diff --git a/src/clients/meta/MetaClient.cpp b/src/clients/meta/MetaClient.cpp
index 0e4fb05d239..17348fef4a7 100644
--- a/src/clients/meta/MetaClient.cpp
+++ b/src/clients/meta/MetaClient.cpp
@@ -865,8 +865,6 @@ Status MetaClient::handleResponse(const RESP& resp) {
       return Status::Error("Zone is empty!");
     case nebula::cpp2::ErrorCode::E_STORE_FAILURE:
       return Status::Error("Store failure!");
-    case nebula::cpp2::ErrorCode::E_STORE_SEGMENT_ILLEGAL:
-      return Status::Error("Store segment illegal!");
     case nebula::cpp2::ErrorCode::E_BAD_BALANCE_PLAN:
       return Status::Error("Bad balance plan!");
     case nebula::cpp2::ErrorCode::E_BALANCED:
@@ -1420,134 +1418,6 @@ StatusOr<std::vector<std::string>> MetaClient::getAllEdgeFromCache(const GraphSp
   return it->second;
 }
 
-folly::Future<StatusOr<bool>> MetaClient::multiPut(
-    std::string segment, std::vector<std::pair<std::string, std::string>> pairs) {
-  if (!nebula::meta::checkSegment(segment) || pairs.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::MultiPutReq req;
-  std::vector<nebula::KeyValue> data;
-  data.reserve(pairs.size());
-
-  for (auto& element : pairs) {
-    data.emplace_back(std::move(element));
-  }
-  req.segment_ref() = std::move(segment);
-  req.pairs_ref() = std::move(data);
-  folly::Promise<StatusOr<bool>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_multiPut(request); },
-      [](cpp2::ExecResp&& resp) -> bool {
-        return resp.get_code() == nebula::cpp2::ErrorCode::SUCCEEDED;
-      },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<std::string>> MetaClient::get(std::string segment, std::string key) {
-  if (!nebula::meta::checkSegment(segment) || key.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::GetReq req;
-  req.segment_ref() = std::move(segment);
-  req.key_ref() = std::move(key);
-  folly::Promise<StatusOr<std::string>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_get(request); },
-      [](cpp2::GetResp&& resp) -> std::string { return resp.get_value(); },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<std::vector<std::string>>> MetaClient::multiGet(
-    std::string segment, std::vector<std::string> keys) {
-  if (!nebula::meta::checkSegment(segment) || keys.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::MultiGetReq req;
-  req.segment_ref() = std::move(segment);
-  req.keys_ref() = std::move(keys);
-  folly::Promise<StatusOr<std::vector<std::string>>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_multiGet(request); },
-      [](cpp2::MultiGetResp&& resp) -> std::vector<std::string> { return resp.get_values(); },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<std::vector<std::string>>> MetaClient::scan(std::string segment,
-                                                                   std::string start,
-                                                                   std::string end) {
-  if (!nebula::meta::checkSegment(segment) || start.empty() || end.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::ScanReq req;
-  req.segment_ref() = std::move(segment);
-  req.start_ref() = std::move(start);
-  req.end_ref() = std::move(end);
-  folly::Promise<StatusOr<std::vector<std::string>>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_scan(request); },
-      [](cpp2::ScanResp&& resp) -> std::vector<std::string> { return resp.get_values(); },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<bool>> MetaClient::remove(std::string segment, std::string key) {
-  if (!nebula::meta::checkSegment(segment) || key.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::RemoveReq req;
-  req.segment_ref() = std::move(segment);
-  req.key_ref() = std::move(key);
-  folly::Promise<StatusOr<bool>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_remove(request); },
-      [](cpp2::ExecResp&& resp) -> bool {
-        return resp.get_code() == nebula::cpp2::ErrorCode::SUCCEEDED;
-      },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<bool>> MetaClient::removeRange(std::string segment,
-                                                      std::string start,
-                                                      std::string end) {
-  if (!nebula::meta::checkSegment(segment) || start.empty() || end.empty()) {
-    return Status::Error("arguments invalid!");
-  }
-
-  cpp2::RemoveRangeReq req;
-  req.segment_ref() = std::move(segment);
-  req.start_ref() = std::move(start);
-  req.end_ref() = std::move(end);
-  folly::Promise<StatusOr<bool>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_removeRange(request); },
-      [](cpp2::ExecResp&& resp) -> bool {
-        return resp.get_code() == nebula::cpp2::ErrorCode::SUCCEEDED;
-      },
-      std::move(promise));
-  return future;
-}
-
 PartsMap MetaClient::getPartsMapFromCache(const HostAddr& host) {
   folly::rcu_reader guard;
   const auto& metadata = *metadata_.load();
@@ -2791,50 +2661,6 @@ folly::Future<StatusOr<std::vector<cpp2::RoleItem>>> MetaClient::getUserRoles(st
   return future;
 }
 
-folly::Future<StatusOr<std::string>> MetaClient::getTagDefaultValue(GraphSpaceID spaceId,
-                                                                    TagID tagId,
-                                                                    const std::string& field) {
-  cpp2::GetReq req;
-  static std::string defaultKey = "__default__";
-  req.segment_ref() = defaultKey;
-  std::string key;
-  key.reserve(64);
-  key.append(reinterpret_cast<const char*>(&spaceId), sizeof(GraphSpaceID));
-  key.append(reinterpret_cast<const char*>(&tagId), sizeof(TagID));
-  key.append(field);
-  req.key_ref() = std::move(key);
-  folly::Promise<StatusOr<std::string>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_get(request); },
-      [](cpp2::GetResp&& resp) -> std::string { return resp.get_value(); },
-      std::move(promise));
-  return future;
-}
-
-folly::Future<StatusOr<std::string>> MetaClient::getEdgeDefaultValue(GraphSpaceID spaceId,
-                                                                     EdgeType edgeType,
-                                                                     const std::string& field) {
-  cpp2::GetReq req;
-  static std::string defaultKey = "__default__";
-  req.segment_ref() = defaultKey;
-  std::string key;
-  key.reserve(64);
-  key.append(reinterpret_cast<const char*>(&spaceId), sizeof(GraphSpaceID));
-  key.append(reinterpret_cast<const char*>(&edgeType), sizeof(EdgeType));
-  key.append(field);
-  req.key_ref() = std::move(key);
-  folly::Promise<StatusOr<std::string>> promise;
-  auto future = promise.getFuture();
-  getResponse(
-      std::move(req),
-      [](auto client, auto request) { return client->future_get(request); },
-      [](cpp2::GetResp&& resp) -> std::string { return resp.get_value(); },
-      std::move(promise));
-  return future;
-}
-
 folly::Future<StatusOr<bool>> MetaClient::regConfig(const std::vector<cpp2::ConfigItem>& items) {
   cpp2::RegConfigReq req;
   req.items_ref() = items;
diff --git a/src/clients/meta/MetaClient.h b/src/clients/meta/MetaClient.h
index 8ac7e42ff02..0597dd1d5ee 100644
--- a/src/clients/meta/MetaClient.h
+++ b/src/clients/meta/MetaClient.h
@@ -373,25 +373,6 @@ class MetaClient {
 
   folly::Future<StatusOr<std::vector<cpp2::IndexStatus>>> listEdgeIndexStatus(GraphSpaceID spaceId);
 
-  // Operations for custom kv
-  folly::Future<StatusOr<bool>> multiPut(std::string segment,
-                                         std::vector<std::pair<std::string, std::string>> pairs);
-
-  folly::Future<StatusOr<std::string>> get(std::string segment, std::string key);
-
-  folly::Future<StatusOr<std::vector<std::string>>> multiGet(std::string segment,
-                                                             std::vector<std::string> keys);
-
-  folly::Future<StatusOr<std::vector<std::string>>> scan(std::string segment,
-                                                         std::string start,
-                                                         std::string end);
-
-  folly::Future<StatusOr<bool>> remove(std::string segment, std::string key);
-
-  folly::Future<StatusOr<bool>> removeRange(std::string segment,
-                                            std::string start,
-                                            std::string end);
-
   // Operations for users.
   folly::Future<StatusOr<bool>> createUser(std::string account,
                                            std::string password,
@@ -591,14 +572,6 @@ class MetaClient {
 
   const std::vector<HostAddr>& getAddresses();
 
-  folly::Future<StatusOr<std::string>> getTagDefaultValue(GraphSpaceID spaceId,
-                                                          TagID tagId,
-                                                          const std::string& field);
-
-  folly::Future<StatusOr<std::string>> getEdgeDefaultValue(GraphSpaceID spaceId,
-                                                           EdgeType edgeType,
-                                                           const std::string& field);
-
   std::vector<cpp2::RoleItem> getRolesByUserFromCache(const std::string& user);
 
   Status authCheckFromCache(const std::string& account, const std::string& password);
diff --git a/src/common/meta/Common.h b/src/common/meta/Common.h
index 625102c4d71..5b6f9c44e7d 100644
--- a/src/common/meta/Common.h
+++ b/src/common/meta/Common.h
@@ -62,13 +62,6 @@ using RemoteListeners =
     std::unordered_map<GraphSpaceID,
                        std::unordered_map<PartitionID, std::vector<RemoteListenerInfo>>>;
 
-inline bool checkSegment(const std::string& segment) {
-  static const std::regex pattern("^[0-9a-zA-Z]+$");
-  if (!segment.empty() && std::regex_match(segment, pattern)) {
-    return true;
-  }
-  return false;
-}
 
 }  // namespace meta
 }  // namespace nebula
diff --git a/src/common/utils/MetaKeyUtils.cpp b/src/common/utils/MetaKeyUtils.cpp
index a45ad90c002..821d2fda3af 100644
--- a/src/common/utils/MetaKeyUtils.cpp
+++ b/src/common/utils/MetaKeyUtils.cpp
@@ -760,13 +760,6 @@ std::string MetaKeyUtils::indexZoneKey(const std::string& name) {
   return key;
 }
 
-std::string MetaKeyUtils::assembleSegmentKey(const std::string& segment, const std::string& key) {
-  std::string segmentKey;
-  segmentKey.reserve(64);
-  segmentKey.append(segment).append(key.data(), key.size());
-  return segmentKey;
-}
-
 std::string MetaKeyUtils::userPrefix() {
   return kUsersTable;
 }
diff --git a/src/common/utils/MetaKeyUtils.h b/src/common/utils/MetaKeyUtils.h
index 5d463da6c53..777571f5f11 100644
--- a/src/common/utils/MetaKeyUtils.h
+++ b/src/common/utils/MetaKeyUtils.h
@@ -243,8 +243,6 @@ class MetaKeyUtils final {
 
   static std::string indexZoneKey(const std::string& name);
 
-  static std::string assembleSegmentKey(const std::string& segment, const std::string& key);
-
   static std::string userPrefix();
 
   static std::string userKey(const std::string& account);
diff --git a/src/interface/meta.thrift b/src/interface/meta.thrift
index b512c94ec11..b6bbe7fb6e0 100644
--- a/src/interface/meta.thrift
+++ b/src/interface/meta.thrift
@@ -518,58 +518,6 @@ struct GetWorkerIdResp {
     3: i64              workerid,
 }
 
-struct MultiPutReq {
-    // segment is used to avoid conflict with system data.
-    // it should be comprised of numbers and letters.
-    1: binary                   segment,
-    2: list<common.KeyValue>    pairs,
-}
-
-struct GetReq {
-    1: binary segment,
-    2: binary key,
-}
-
-struct GetResp {
-    1: common.ErrorCode code,
-    2: common.HostAddr  leader,
-    3: binary           value,
-}
-
-struct MultiGetReq {
-    1: binary       segment,
-    2: list<binary> keys,
-}
-
-struct MultiGetResp {
-    1: common.ErrorCode code,
-    2: common.HostAddr  leader,
-    3: list<binary>     values,
-}
-
-struct RemoveReq {
-    1: binary segment,
-    2: binary key,
-}
-
-struct RemoveRangeReq {
-    1: binary segment,
-    2: binary start,
-    3: binary end,
-}
-
-struct ScanReq {
-    1: binary segment,
-    2: binary start,
-    3: binary end,
-}
-
-struct ScanResp {
-    1: common.ErrorCode code,
-    2: common.HostAddr  leader,
-    3: list<binary>     values,
-}
-
 struct HBResp {
     1: common.ErrorCode code,
     2: common.HostAddr  leader,
@@ -1220,13 +1168,6 @@ service MetaService {
 
     GetWorkerIdResp getWorkerId(1: GetWorkerIdReq req);
 
-    ExecResp multiPut(1: MultiPutReq req);
-    GetResp get(1: GetReq req);
-    MultiGetResp multiGet(1: MultiGetReq req);
-    ExecResp remove(1: RemoveReq req);
-    ExecResp removeRange(1: RemoveRangeReq req);
-    ScanResp scan(1: ScanReq req);
-
     ExecResp             createTagIndex(1: CreateTagIndexReq req);
     ExecResp             dropTagIndex(1: DropTagIndexReq req );
     GetTagIndexResp      getTagIndex(1: GetTagIndexReq req);
diff --git a/src/meta/ActiveHostsMan.cpp b/src/meta/ActiveHostsMan.cpp
index 0097634bfae..4ab0eaa581f 100644
--- a/src/meta/ActiveHostsMan.cpp
+++ b/src/meta/ActiveHostsMan.cpp
@@ -8,7 +8,6 @@
 #include <thrift/lib/cpp/util/EnumUtils.h>
 
 #include "common/utils/Utils.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 DECLARE_int32(heartbeat_interval_secs);
diff --git a/src/meta/CMakeLists.txt b/src/meta/CMakeLists.txt
index 2ff62fc1fe5..568d308fe35 100644
--- a/src/meta/CMakeLists.txt
+++ b/src/meta/CMakeLists.txt
@@ -38,12 +38,6 @@ nebula_add_library(
     processors/index/ListEdgeIndexesProcessor.cpp
     processors/service/ServiceProcessor.cpp
     processors/index/FTIndexProcessor.cpp
-    processors/kv/GetProcessor.cpp
-    processors/kv/MultiGetProcessor.cpp
-    processors/kv/MultiPutProcessor.cpp
-    processors/kv/RemoveProcessor.cpp
-    processors/kv/RemoveRangeProcessor.cpp
-    processors/kv/ScanProcessor.cpp
     processors/admin/HBProcessor.cpp
     processors/admin/AgentHBProcessor.cpp
     processors/user/AuthenticationProcessor.cpp
diff --git a/src/meta/MetaServiceHandler.cpp b/src/meta/MetaServiceHandler.cpp
index 1ab14cd1f29..8af918c38eb 100644
--- a/src/meta/MetaServiceHandler.cpp
+++ b/src/meta/MetaServiceHandler.cpp
@@ -35,12 +35,6 @@
 #include "meta/processors/job/ListEdgeIndexStatusProcessor.h"
 #include "meta/processors/job/ListTagIndexStatusProcessor.h"
 #include "meta/processors/job/ReportTaskProcessor.h"
-#include "meta/processors/kv/GetProcessor.h"
-#include "meta/processors/kv/MultiGetProcessor.h"
-#include "meta/processors/kv/MultiPutProcessor.h"
-#include "meta/processors/kv/RemoveProcessor.h"
-#include "meta/processors/kv/RemoveRangeProcessor.h"
-#include "meta/processors/kv/ScanProcessor.h"
 #include "meta/processors/listener/ListenerProcessor.h"
 #include "meta/processors/parts/AlterSpaceProcessor.h"
 #include "meta/processors/parts/CreateSpaceAsProcessor.h"
@@ -157,38 +151,6 @@ folly::Future<cpp2::GetPartsAllocResp> MetaServiceHandler::future_getPartsAlloc(
   RETURN_FUTURE(processor);
 }
 
-folly::Future<cpp2::ExecResp> MetaServiceHandler::future_multiPut(const cpp2::MultiPutReq& req) {
-  auto* processor = MultiPutProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
-folly::Future<cpp2::GetResp> MetaServiceHandler::future_get(const cpp2::GetReq& req) {
-  auto* processor = GetProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
-folly::Future<cpp2::MultiGetResp> MetaServiceHandler::future_multiGet(
-    const cpp2::MultiGetReq& req) {
-  auto* processor = MultiGetProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
-folly::Future<cpp2::ScanResp> MetaServiceHandler::future_scan(const cpp2::ScanReq& req) {
-  auto* processor = ScanProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
-folly::Future<cpp2::ExecResp> MetaServiceHandler::future_remove(const cpp2::RemoveReq& req) {
-  auto* processor = RemoveProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
-folly::Future<cpp2::ExecResp> MetaServiceHandler::future_removeRange(
-    const cpp2::RemoveRangeReq& req) {
-  auto* processor = RemoveRangeProcessor::instance(kvstore_);
-  RETURN_FUTURE(processor);
-}
-
 folly::Future<cpp2::ExecResp> MetaServiceHandler::future_createTag(const cpp2::CreateTagReq& req) {
   auto* processor = CreateTagProcessor::instance(kvstore_);
   RETURN_FUTURE(processor);
diff --git a/src/meta/MetaServiceHandler.h b/src/meta/MetaServiceHandler.h
index 3d9f7c7df20..a9c36b67d70 100644
--- a/src/meta/MetaServiceHandler.h
+++ b/src/meta/MetaServiceHandler.h
@@ -55,21 +55,6 @@ class MetaServiceHandler final : public cpp2::MetaServiceSvIf {
   folly::Future<cpp2::GetPartsAllocResp> future_getPartsAlloc(
       const cpp2::GetPartsAllocReq& req) override;
 
-  /**
-   * Custom kv related operations.
-   * */
-  folly::Future<cpp2::ExecResp> future_multiPut(const cpp2::MultiPutReq& req) override;
-
-  folly::Future<cpp2::GetResp> future_get(const cpp2::GetReq& req) override;
-
-  folly::Future<cpp2::MultiGetResp> future_multiGet(const cpp2::MultiGetReq& req) override;
-
-  folly::Future<cpp2::ExecResp> future_remove(const cpp2::RemoveReq& req) override;
-
-  folly::Future<cpp2::ExecResp> future_removeRange(const cpp2::RemoveRangeReq& req) override;
-
-  folly::Future<cpp2::ScanResp> future_scan(const cpp2::ScanReq& req) override;
-
   /**
    * Schema related operations.
    * */
diff --git a/src/meta/common/MetaCommon.h b/src/meta/common/MetaCommon.h
deleted file mode 100644
index 4d320577386..00000000000
--- a/src/meta/common/MetaCommon.h
+++ /dev/null
@@ -1,60 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_COMMON_H_
-#define META_COMMON_H_
-
-#include "common/base/Base.h"
-#include "common/base/Status.h"
-#include "common/utils/MetaKeyUtils.h"
-#include "interface/gen-cpp2/meta_types.h"
-#include "kvstore/KVStore.h"
-#include "meta/processors/Common.h"
-
-namespace nebula {
-namespace meta {
-
-class MetaCommon final {
- public:
-  MetaCommon() = delete;
-
-  static bool checkSegment(const std::string& segment) {
-    static const std::regex pattern("^[0-9a-zA-Z]+$");
-    if (!segment.empty() && std::regex_match(segment, pattern)) {
-      return true;
-    }
-    return false;
-  }
-
-  static bool saveRebuildStatus(kvstore::KVStore* kvstore,
-                                std::string statusKey,
-                                std::string&& statusValue) {
-    std::vector<kvstore::KV> status{
-        std::make_pair(std::move(statusKey), std::forward<std::string>(statusValue))};
-    folly::Baton<true, std::atomic> baton;
-    auto ret = nebula::cpp2::ErrorCode::SUCCEEDED;
-    kvstore->asyncMultiPut(kDefaultSpaceId,
-                           kDefaultPartId,
-                           std::move(status),
-                           [&ret, &baton](nebula::cpp2::ErrorCode code) {
-                             if (nebula::cpp2::ErrorCode::SUCCEEDED != code) {
-                               ret = code;
-                               LOG(INFO) << "Put data error on meta server";
-                             }
-                             baton.post();
-                           });
-    baton.wait();
-    if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Save Status Failed";
-      return false;
-    }
-    return true;
-  }
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_COMMON_H_
diff --git a/src/meta/http/MetaHttpDownloadHandler.cpp b/src/meta/http/MetaHttpDownloadHandler.cpp
index 03167f1b1cd..6c88e6927db 100644
--- a/src/meta/http/MetaHttpDownloadHandler.cpp
+++ b/src/meta/http/MetaHttpDownloadHandler.cpp
@@ -92,7 +92,7 @@ void MetaHttpDownloadHandler::onEOM() noexcept {
           .body("SSTFile dispatch successfully")
           .sendWithEOM();
     } else {
-      LOG(ERROR) << "SSTFile dispatch failed";
+      LOG(INFO) << "SSTFile dispatch failed";
       ResponseBuilder(downstream_)
           .status(WebServiceUtils::to(HttpStatusCode::FORBIDDEN),
                   WebServiceUtils::toString(HttpStatusCode::FORBIDDEN))
@@ -100,7 +100,7 @@ void MetaHttpDownloadHandler::onEOM() noexcept {
           .sendWithEOM();
     }
   } else {
-    LOG(ERROR) << "Hadoop Home not exist";
+    LOG(INFO) << "Hadoop Home not exist";
     ResponseBuilder(downstream_)
         .status(WebServiceUtils::to(HttpStatusCode::NOT_FOUND),
                 WebServiceUtils::toString(HttpStatusCode::NOT_FOUND))
@@ -117,8 +117,8 @@ void MetaHttpDownloadHandler::requestComplete() noexcept {
 }
 
 void MetaHttpDownloadHandler::onError(ProxygenError error) noexcept {
-  LOG(ERROR) << "Web Service MetaHttpDownloadHandler got error : "
-             << proxygen::getErrorString(error);
+  LOG(INFO) << "Web Service MetaHttpDownloadHandler got error : "
+            << proxygen::getErrorString(error);
 }
 
 bool MetaHttpDownloadHandler::dispatchSSTFiles(const std::string &hdfsHost,
@@ -126,7 +126,7 @@ bool MetaHttpDownloadHandler::dispatchSSTFiles(const std::string &hdfsHost,
                                                const std::string &hdfsPath) {
   auto result = helper_->ls(hdfsHost, hdfsPort, hdfsPath);
   if (!result.ok()) {
-    LOG(ERROR) << "Dispatch SSTFile Failed";
+    LOG(INFO) << "Dispatch SSTFile Failed";
     return false;
   }
   std::vector<std::string> files;
@@ -136,7 +136,7 @@ bool MetaHttpDownloadHandler::dispatchSSTFiles(const std::string &hdfsHost,
   auto prefix = MetaKeyUtils::partPrefix(spaceID_);
   auto ret = kvstore_->prefix(0, 0, prefix, &iter);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Fetch Parts Failed";
+    LOG(INFO) << "Fetch Parts Failed";
     return false;
   }
 
@@ -187,7 +187,7 @@ bool MetaHttpDownloadHandler::dispatchSSTFiles(const std::string &hdfsHost,
   auto tries = folly::collectAll(std::move(futures)).get();
   for (const auto &t : tries) {
     if (t.hasException()) {
-      LOG(ERROR) << "Download Failed: " << t.exception();
+      LOG(INFO) << "Download Failed: " << t.exception();
       successfully = false;
       break;
     }
diff --git a/src/meta/http/MetaHttpDownloadHandler.h b/src/meta/http/MetaHttpDownloadHandler.h
index 18efb020ef8..fff54645ce6 100644
--- a/src/meta/http/MetaHttpDownloadHandler.h
+++ b/src/meta/http/MetaHttpDownloadHandler.h
@@ -19,6 +19,12 @@ namespace meta {
 
 using nebula::HttpCode;
 
+/**
+ * @brief Download sst files from hdfs to every storaged download folder.
+ *        It will send download http request to every storaged, letting them
+ *        download the corressponding sst files.
+ *
+ */
 class MetaHttpDownloadHandler : public proxygen::RequestHandler {
  public:
   MetaHttpDownloadHandler() = default;
diff --git a/src/meta/http/MetaHttpIngestHandler.cpp b/src/meta/http/MetaHttpIngestHandler.cpp
index a11f8675fc8..ff91c27166f 100644
--- a/src/meta/http/MetaHttpIngestHandler.cpp
+++ b/src/meta/http/MetaHttpIngestHandler.cpp
@@ -84,7 +84,7 @@ void MetaHttpIngestHandler::onEOM() noexcept {
         .body("SSTFile ingest successfully")
         .sendWithEOM();
   } else {
-    LOG(ERROR) << "SSTFile ingest failed";
+    LOG(INFO) << "SSTFile ingest failed";
     ResponseBuilder(downstream_)
         .status(WebServiceUtils::to(HttpStatusCode::FORBIDDEN),
                 WebServiceUtils::toString(HttpStatusCode::FORBIDDEN))
@@ -102,7 +102,7 @@ void MetaHttpIngestHandler::requestComplete() noexcept {
 }
 
 void MetaHttpIngestHandler::onError(ProxygenError error) noexcept {
-  LOG(ERROR) << "Web Service MetaHttpIngestHandler got error : " << proxygen::getErrorString(error);
+  LOG(INFO) << "Web Service MetaHttpIngestHandler got error : " << proxygen::getErrorString(error);
 }
 
 bool MetaHttpIngestHandler::ingestSSTFiles(GraphSpaceID space) {
@@ -113,7 +113,7 @@ bool MetaHttpIngestHandler::ingestSSTFiles(GraphSpaceID space) {
   static const PartitionID metaPartId = 0;
   auto ret = kvstore_->prefix(metaSpaceId, metaPartId, prefix, &iter);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Fetch Parts Failed";
+    LOG(INFO) << "Fetch Parts Failed";
     return false;
   }
 
@@ -144,7 +144,7 @@ bool MetaHttpIngestHandler::ingestSSTFiles(GraphSpaceID space) {
   auto tries = folly::collectAll(std::move(futures)).get();
   for (const auto &t : tries) {
     if (t.hasException()) {
-      LOG(ERROR) << "Ingest Failed: " << t.exception();
+      LOG(INFO) << "Ingest Failed: " << t.exception();
       successfully = false;
       break;
     }
diff --git a/src/meta/http/MetaHttpIngestHandler.h b/src/meta/http/MetaHttpIngestHandler.h
index 9cfc1400430..70ff7ece64d 100644
--- a/src/meta/http/MetaHttpIngestHandler.h
+++ b/src/meta/http/MetaHttpIngestHandler.h
@@ -18,6 +18,13 @@ namespace meta {
 
 using nebula::HttpCode;
 
+/**
+ * @brief Ingest should be called after download successfully.
+ *        It will instruct relative storaged to ingest sst files
+ *        from local download folder by sending http request.
+ *        It will handle one space each time.
+ *
+ */
 class MetaHttpIngestHandler : public proxygen::RequestHandler {
  public:
   MetaHttpIngestHandler() = default;
diff --git a/src/meta/http/MetaHttpReplaceHostHandler.cpp b/src/meta/http/MetaHttpReplaceHostHandler.cpp
index 23fa54fcf39..ad3cbc0f062 100644
--- a/src/meta/http/MetaHttpReplaceHostHandler.cpp
+++ b/src/meta/http/MetaHttpReplaceHostHandler.cpp
@@ -84,7 +84,7 @@ void MetaHttpReplaceHostHandler::onEOM() noexcept {
         .body("Replace Host successfully")
         .sendWithEOM();
   } else {
-    LOG(ERROR) << "Replace Host failed";
+    LOG(INFO) << "Replace Host failed";
     ResponseBuilder(downstream_)
         .status(WebServiceUtils::to(HttpStatusCode::FORBIDDEN),
                 WebServiceUtils::toString(HttpStatusCode::FORBIDDEN))
@@ -102,8 +102,8 @@ void MetaHttpReplaceHostHandler::requestComplete() noexcept {
 }
 
 void MetaHttpReplaceHostHandler::onError(ProxygenError error) noexcept {
-  LOG(ERROR) << "Web Service MetaHttpReplaceHostHandler got error : "
-             << proxygen::getErrorString(error);
+  LOG(INFO) << "Web Service MetaHttpReplaceHostHandler got error : "
+            << proxygen::getErrorString(error);
 }
 
 bool MetaHttpReplaceHostHandler::replaceHost(std::string ipv4From, std::string ipv4To) {
@@ -113,7 +113,7 @@ bool MetaHttpReplaceHostHandler::replaceHost(std::string ipv4From, std::string i
   auto kvRet = kvstore_->prefix(kDefaultSpaceId, kDefaultPartId, spacePrefix, &iter);
   if (kvRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
     errMsg_ = folly::stringPrintf("can't get space prefix=%s", spacePrefix.c_str());
-    LOG(ERROR) << errMsg_;
+    LOG(INFO) << errMsg_;
     return false;
   }
 
@@ -131,7 +131,7 @@ bool MetaHttpReplaceHostHandler::replaceHost(std::string ipv4From, std::string i
     kvRet = kvstore_->prefix(kDefaultSpaceId, kDefaultPartId, partPrefix, &iter);
     if (kvRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
       errMsg_ = folly::stringPrintf("can't get partPrefix=%s", partPrefix.c_str());
-      LOG(ERROR) << errMsg_;
+      LOG(INFO) << errMsg_;
       return false;
     }
 
diff --git a/src/meta/http/MetaHttpReplaceHostHandler.h b/src/meta/http/MetaHttpReplaceHostHandler.h
index 48cccaca157..b1211a0e798 100644
--- a/src/meta/http/MetaHttpReplaceHostHandler.h
+++ b/src/meta/http/MetaHttpReplaceHostHandler.h
@@ -17,6 +17,13 @@ namespace meta {
 
 using nebula::HttpCode;
 
+/**
+ * @brief It will replace host info in meta partition table from
+ *        backup host to current cluster host.
+ *        It should be called after ingesting meta sst files when
+ *        restore cluster.
+ *
+ */
 class MetaHttpReplaceHostHandler : public proxygen::RequestHandler {
   FRIEND_TEST(MetaHttpReplaceHandlerTest, FooTest);
 
diff --git a/src/meta/processors/BaseProcessor-inl.h b/src/meta/processors/BaseProcessor-inl.h
index 03780043fd5..2115725a6cd 100644
--- a/src/meta/processors/BaseProcessor-inl.h
+++ b/src/meta/processors/BaseProcessor-inl.h
@@ -166,7 +166,7 @@ ErrorOr<nebula::cpp2::ErrorCode, int32_t> BaseProcessor<RESP>::autoIncrementId()
 template <typename RESP>
 ErrorOr<nebula::cpp2::ErrorCode, int32_t> BaseProcessor<RESP>::getAvailableGlobalId() {
   // A read lock has been added before call
-  static const std::string kIdKey = "__id__";
+  static const std::string kIdKey = MetaKeyUtils::idKey();
   int32_t id;
   std::string val;
   auto ret = kvstore_->get(kDefaultSpaceId, kDefaultPartId, kIdKey, &val);
@@ -279,7 +279,7 @@ nebula::cpp2::ErrorCode BaseProcessor<RESP>::includeByZone(const std::vector<Hos
   nebula::cpp2::ErrorCode code = nebula::cpp2::ErrorCode::SUCCEEDED;
   if (!nebula::ok(iterRet)) {
     code = nebula::error(iterRet);
-    LOG(ERROR) << "Get zones failed, error: " << apache::thrift::util::enumNameSafe(code);
+    LOG(INFO) << "Get zones failed, error: " << apache::thrift::util::enumNameSafe(code);
     return code;
   }
 
@@ -289,7 +289,7 @@ nebula::cpp2::ErrorCode BaseProcessor<RESP>::includeByZone(const std::vector<Hos
     auto zoneHosts = MetaKeyUtils::parseZoneHosts(iter->val());
     for (const auto& host : hosts) {
       if (std::find(zoneHosts.begin(), zoneHosts.end(), host) != zoneHosts.end()) {
-        LOG(ERROR) << "Host overlap found in zone " << name;
+        LOG(INFO) << "Host overlap found in zone " << name;
         code = nebula::cpp2::ErrorCode::E_CONFLICT;
         break;
       }
@@ -356,7 +356,7 @@ ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> BaseProcessor<RESP>::getLatestTag
   const auto& key = MetaKeyUtils::schemaTagPrefix(spaceId, tagId);
   auto ret = doPrefix(key);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Tag Prefix " << key << " failed";
+    LOG(INFO) << "Tag Prefix " << key << " failed";
     return nebula::error(ret);
   }
 
@@ -364,7 +364,7 @@ ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> BaseProcessor<RESP>::getLatestTag
   if (iter->valid()) {
     return MetaKeyUtils::parseSchema(iter->val());
   } else {
-    LOG(ERROR) << "Tag Prefix " << key << " not found";
+    LOG(INFO) << "Tag Prefix " << key << " not found";
     return nebula::cpp2::ErrorCode::E_TAG_NOT_FOUND;
   }
 }
@@ -375,7 +375,7 @@ ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> BaseProcessor<RESP>::getLatestEdg
   const auto& key = MetaKeyUtils::schemaEdgePrefix(spaceId, edgeType);
   auto ret = doPrefix(key);
   if (!nebula::ok(ret)) {
-    LOG(ERROR) << "Edge Prefix " << key << " failed";
+    LOG(INFO) << "Edge Prefix " << key << " failed";
     return nebula::error(ret);
   }
 
@@ -383,7 +383,7 @@ ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> BaseProcessor<RESP>::getLatestEdg
   if (iter->valid()) {
     return MetaKeyUtils::parseSchema(iter->val());
   } else {
-    LOG(ERROR) << "Edge Prefix " << key << " not found";
+    LOG(INFO) << "Edge Prefix " << key << " not found";
     return nebula::cpp2::ErrorCode::E_EDGE_NOT_FOUND;
   }
 }
@@ -490,8 +490,8 @@ ErrorOr<nebula::cpp2::ErrorCode, std::vector<cpp2::IndexItem>> BaseProcessor<RES
   auto iterRet = doPrefix(indexPrefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Tag or edge index prefix failed, error :"
-               << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Tag or edge index prefix failed, error :"
+              << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
   auto indexIter = nebula::value(iterRet).get();
@@ -509,6 +509,7 @@ ErrorOr<nebula::cpp2::ErrorCode, std::vector<cpp2::IndexItem>> BaseProcessor<RES
   }
   return items;
 }
+
 template <typename RESP>
 ErrorOr<nebula::cpp2::ErrorCode, cpp2::FTIndex> BaseProcessor<RESP>::getFTIndex(
     GraphSpaceID spaceId, int32_t tagOrEdge) {
@@ -516,8 +517,8 @@ ErrorOr<nebula::cpp2::ErrorCode, cpp2::FTIndex> BaseProcessor<RESP>::getFTIndex(
   auto iterRet = doPrefix(indexPrefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Tag or edge fulltext index prefix failed, error :"
-               << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Tag or edge fulltext index prefix failed, error :"
+              << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
   auto indexIter = nebula::value(iterRet).get();
@@ -550,8 +551,8 @@ nebula::cpp2::ErrorCode BaseProcessor<RESP>::indexCheck(
             return tCol.name == iCol.name;
           });
           if (it != indexCols.end()) {
-            LOG(ERROR) << "Index conflict, index :" << index.get_index_name()
-                       << ", column : " << tCol.name;
+            LOG(INFO) << "Index conflict, index :" << index.get_index_name()
+                      << ", column : " << tCol.name;
             return nebula::cpp2::ErrorCode::E_CONFLICT;
           }
         }
@@ -560,6 +561,7 @@ nebula::cpp2::ErrorCode BaseProcessor<RESP>::indexCheck(
   }
   return nebula::cpp2::ErrorCode::SUCCEEDED;
 }
+
 template <typename RESP>
 nebula::cpp2::ErrorCode BaseProcessor<RESP>::ftIndexCheck(
     const std::vector<std::string>& cols, const std::vector<cpp2::AlterSchemaItem>& alterItems) {
@@ -571,7 +573,7 @@ nebula::cpp2::ErrorCode BaseProcessor<RESP>::ftIndexCheck(
         auto it =
             std::find_if(cols.begin(), cols.end(), [&](const auto& c) { return c == iCol.name; });
         if (it != cols.end()) {
-          LOG(ERROR) << "fulltext index conflict";
+          LOG(INFO) << "fulltext index conflict";
           return nebula::cpp2::ErrorCode::E_CONFLICT;
         }
       }
@@ -592,7 +594,7 @@ bool BaseProcessor<RESP>::checkIndexExist(const std::vector<cpp2::IndexFieldDef>
       return false;
     }
   }
-  LOG(ERROR) << "Index " << item.get_index_name() << " has existed";
+  LOG(INFO) << "Index " << item.get_index_name() << " has existed";
   return true;
 }
 
diff --git a/src/meta/processors/BaseProcessor.h b/src/meta/processors/BaseProcessor.h
index 76430930cf4..2984268524b 100644
--- a/src/meta/processors/BaseProcessor.h
+++ b/src/meta/processors/BaseProcessor.h
@@ -20,7 +20,6 @@
 #include "kvstore/KVStore.h"
 #include "meta/ActiveHostsMan.h"
 #include "meta/MetaServiceUtils.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 namespace nebula {
@@ -43,16 +42,6 @@ using SignType = storage::cpp2::EngineSignType;
     break;                                          \
   }
 
-/**
- * Check segment is consist of numbers and letters and should not empty.
- * */
-#define CHECK_SEGMENT(segment)                                         \
-  if (!MetaCommon::checkSegment(segment)) {                            \
-    handleErrorCode(nebula::cpp2::ErrorCode::E_STORE_SEGMENT_ILLEGAL); \
-    onFinished();                                                      \
-    return;                                                            \
-  }
-
 template <typename RESP>
 class BaseProcessor {
  public:
@@ -66,13 +55,21 @@ class BaseProcessor {
 
  protected:
   /**
-   * Destroy current instance when finished.
-   * */
+   * @brief Destroy current instance when finished.
+   *
+   */
   virtual void onFinished() {
     promise_.setValue(std::move(resp_));
     delete this;
   }
 
+  /**
+   * @brief Set error code and handle leader changed.
+   *
+   * @param code
+   * @param spaceId
+   * @param partId
+   */
   void handleErrorCode(nebula::cpp2::ErrorCode code,
                        GraphSpaceID spaceId = kDefaultSpaceId,
                        PartitionID partId = kDefaultPartId) {
@@ -82,6 +79,12 @@ class BaseProcessor {
     }
   }
 
+  /**
+   * @brief Set leader address to reponse.
+   *
+   * @param spaceId
+   * @param partId
+   */
   void handleLeaderChanged(GraphSpaceID spaceId, PartitionID partId) {
     auto leaderRet = kvstore_->partLeader(spaceId, partId);
     if (ok(leaderRet)) {
@@ -120,153 +123,379 @@ class BaseProcessor {
   }
 
   /**
-   * General put function.
-   * */
+   * @brief Batch put data to meta kv store synchronously.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param data kv pairs to put
+   */
   void doPut(std::vector<kvstore::KV> data);
 
+  /**
+   * @brief Get the iterator on given meta prefix.
+   *
+   * @tparam RESP
+   * @param key
+   * @param canReadFromFollower read from follower's local
+   * @return ErrorOr<nebula::cpp2::ErrorCode, std::unique_ptr<kvstore::KVIterator>>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, std::unique_ptr<kvstore::KVIterator>> doPrefix(
       const std::string& key, bool canReadFromFollower = false);
 
   /**
-   * General get function.
-   * */
+   * @brief Get the given key's value
+   *
+   * @tparam RESP
+   * @param key
+   * @return ErrorOr<nebula::cpp2::ErrorCode, std::string>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, std::string> doGet(const std::string& key);
 
   /**
-   * General multi get function.
-   * */
+   * @brief Multiple get for given keys.
+   *
+   * @tparam RESP
+   * @param keys
+   * @return ErrorOr<nebula::cpp2::ErrorCode, std::vector<std::string>>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, std::vector<std::string>> doMultiGet(
       const std::vector<std::string>& keys);
 
   /**
-   * General remove function.
-   * */
+   * @brief Remove given keys from kv store.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param key
+   */
   void doRemove(const std::string& key);
 
   /**
-   * Remove keys from start to end, doesn't contain end.
-   * */
+   * @brief Range remove.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param start
+   * @param end
+   */
   void doRemoveRange(const std::string& start, const std::string& end);
 
   /**
-   * Scan keys from start to end, doesn't contain end.
-   * */
+   * @brief Range scan.
+   *
+   * @tparam RESP
+   * @param start
+   * @param end
+   * @return ErrorOr<nebula::cpp2::ErrorCode, std::vector<std::string>>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, std::vector<std::string>> doScan(const std::string& start,
                                                                     const std::string& end);
   /**
-   * General multi remove function.
-   **/
+   * @brief Batch remove.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param keys
+   */
   void doMultiRemove(std::vector<std::string> keys);
 
   /**
-   * General batch function.
-   **/
+   * @brief Batch general operation.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param batchOp
+   */
   void doBatchOperation(std::string batchOp);
 
   /**
-   * Get one auto-increment Id.
-   * */
+   * @brief Increment global auto-incremental id and then return it.
+   *        Note that it has side effect: it will set the code to the resp_.
+   *
+   * @tparam RESP
+   * @return ErrorOr<nebula::cpp2::ErrorCode, int32_t>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, int32_t> autoIncrementId();
 
   /**
-   * Get the current available global id
-   **/
+   * @brief Get global incremental id without incrementing it.
+   *
+   * @tparam RESP
+   * @return ErrorOr<nebula::cpp2::ErrorCode, int32_t>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, int32_t> getAvailableGlobalId();
 
   /**
-   * Get one auto-increment Id in spaceId.
-   * */
+   * @brief Increment space auto-incremental id and then return it.
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @return ErrorOr<nebula::cpp2::ErrorCode, int32_t>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, int32_t> autoIncrementIdInSpace(GraphSpaceID spaceId);
 
   /**
-   * Check spaceId exist or not.
-   * */
+   * @brief Check if given space exist or not.
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @return SUCCEEDED means exist, E_SPACE_NOT_FOUND means not, others means error.
+   */
   nebula::cpp2::ErrorCode spaceExist(GraphSpaceID spaceId);
 
   /**
-   * Check user exist or not.
-   **/
+   * @brief Check if given user exist or not.
+   *
+   * @tparam RESP
+   * @param account
+   * @return SUCCEEDED means exist, E_USER_NOT_FOUND means not, others means error.
+   */
   nebula::cpp2::ErrorCode userExist(const std::string& account);
 
   /**
-   * Check machine has been registered or not.
-   * */
+   * @brief Check if given machine exist.
+   *
+   * @tparam RESP
+   * @param machineKey
+   * @return SUCCEEDED means exist, E_NOT_FOUND means not, others means error.
+   */
   nebula::cpp2::ErrorCode machineExist(const std::string& machineKey);
 
+  /**
+   * @brief Check if given host exist.
+   *
+   * @tparam RESP
+   * @param hostKey
+   * @return SUCCEEDED means exist, E_NOT_FOUND means not, others means error.
+   */
   nebula::cpp2::ErrorCode hostExist(const std::string& hostKey);
 
   /**
-   * Check hosts has been include by zone or not.
-   * */
+   * @brief Check if any host in host list included by any zone.
+   *
+   * @tparam RESP
+   * @param hosts
+   * @return nebula::cpp1::ErrorCode
+   */
   nebula::cpp2::ErrorCode includeByZone(const std::vector<HostAddr>& hosts);
 
   /**
-   * Return the spaceId for name.
-   * */
+   * @brief Get space id by space name
+   *
+   * @tparam RESP
+   * @param name
+   * @return ErrorOr<nebula::cpp2::ErrorCode, GraphSpaceID>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, GraphSpaceID> getSpaceId(const std::string& name);
 
   /**
-   * Return the tagId for name.
+   * @brief Get tag id by space id and tag name
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param name tag name
+   * @return ErrorOr<nebula::cpp2::ErrorCode, TagID>
    */
   ErrorOr<nebula::cpp2::ErrorCode, TagID> getTagId(GraphSpaceID spaceId, const std::string& name);
 
   /**
-   * Fetch the latest version tag's schema.
+   * @brief Fetch the latest version tag's schema by space id and tag id
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param tagId
+   * @return ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema>
    */
   ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> getLatestTagSchema(GraphSpaceID spaceId,
                                                                     const TagID tagId);
 
   /**
-   * Return the edgeType for name.
+   * @brief Get edge type by space id and edge name
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param name edge name
+   * @return ErrorOr<nebula::cpp2::ErrorCode, EdgeType>
    */
   ErrorOr<nebula::cpp2::ErrorCode, EdgeType> getEdgeType(GraphSpaceID spaceId,
                                                          const std::string& name);
 
   /**
-   * Fetch the latest version edge's schema.
+   * @brief Retch the latest version edge's schema by space id and tag id
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param edgeType
+   * @return ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema>
    */
   ErrorOr<nebula::cpp2::ErrorCode, cpp2::Schema> getLatestEdgeSchema(GraphSpaceID spaceId,
                                                                      const EdgeType edgeType);
 
+  /**
+   * @brief Get index id by space id and index name
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param indexName
+   * @return ErrorOr<nebula::cpp2::ErrorCode, IndexID>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, IndexID> getIndexID(GraphSpaceID spaceId,
                                                        const std::string& indexName);
 
+  /**
+   * @brief Check if password identical or not.
+   *
+   * @tparam RESP
+   * @param account
+   * @param password
+   * @return ErrorOr<nebula::cpp2::ErrorCode, bool>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, bool> checkPassword(const std::string& account,
                                                        const std::string& password);
 
+  /**
+   * @brief Put data to kvstore synchronously without side effect.
+   *
+   * @tparam RESP
+   * @param data
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode doSyncPut(std::vector<kvstore::KV> data);
 
+  /**
+   * @brief Put data to the kvstore synchronously. If finished successfully,
+   *        it will update the LastUpdateTime, indicating the metaclient should refresh
+   *        its local schema cache.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param data
+   */
   void doSyncPutAndUpdate(std::vector<kvstore::KV> data);
 
+  /**
+   * @brief Remove data from the kvstore synchronously. If finished successfully,
+   *        it will update the LastUpdateTime, indicating the metaclient should refresh
+   *        its local schema cache.
+   *        Note that it has side effect: it will set the code to the resp_,
+   *        and delete the processor instance. So, it could be only used
+   *        in the Processor:process() end.
+   *
+   * @tparam RESP
+   * @param keys
+   */
   void doSyncMultiRemoveAndUpdate(std::vector<std::string> keys);
 
   /**
-   * Check the edge or tag contains indexes when alter it.
-   **/
+   * @brief Check if tag/edge contains index when alter it.
+   *
+   * @tparam RESP
+   * @param items
+   * @param alterItems
+   * @return ErrorCode::E_CONFLICT if contains
+   */
   nebula::cpp2::ErrorCode indexCheck(const std::vector<cpp2::IndexItem>& items,
                                      const std::vector<cpp2::AlterSchemaItem>& alterItems);
 
+  /**
+   * @brief Check if tag/edge containes full text index when alter it.
+   *
+   * @tparam RESP
+   * @param cols
+   * @param alterItems
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode ftIndexCheck(const std::vector<std::string>& cols,
                                        const std::vector<cpp2::AlterSchemaItem>& alterItems);
 
+  /**
+   * @brief List all tag/edge index for given space and tag/edge id.
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param tagOrEdge tag id or edge id
+   * @return ErrorOr<nebula::cpp2::ErrorCode, std::vector<cpp2::IndexItem>>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, std::vector<cpp2::IndexItem>> getIndexes(GraphSpaceID spaceId,
                                                                             int32_t tagOrEdge);
 
+  /**
+   * @brief Get all full text indexes for given space and tag/edge id.
+   *
+   * @tparam RESP
+   * @param spaceId
+   * @param tagOrEdge
+   * @return ErrorOr<nebula::cpp2::ErrorCode, cpp2::FTIndex>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, cpp2::FTIndex> getFTIndex(GraphSpaceID spaceId,
                                                              int32_t tagOrEdge);
 
+  /**
+   * @brief Check if index on given fields alredy exist.
+   *
+   * @tparam RESP
+   * @param fields
+   * @param item
+   * @return true
+   * @return false
+   */
   bool checkIndexExist(const std::vector<cpp2::IndexFieldDef>& fields, const cpp2::IndexItem& item);
 
+  /**
+   * @brief Get zone id by zone name
+   *
+   * @tparam RESP
+   * @param zoneName
+   * @return ErrorOr<nebula::cpp2::ErrorCode, ZoneID>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, ZoneID> getZoneId(const std::string& zoneName);
 
+  /**
+   * @brief Check if given space exist given type's listener.
+   *
+   * @tparam RESP
+   * @param space
+   * @param type
+   * @return nebula::cpp2::ErrorCode
+   */
   nebula::cpp2::ErrorCode listenerExist(GraphSpaceID space, cpp2::ListenerType type);
 
-  // A direct value of true means that data will not be written to follow via
-  // the raft protocol, but will be written directly to local disk
+  /**
+   * @brief Used in BR, after restore meta data, it will replace partition info from
+   *        current ip to backup ip.
+   *
+   * @param ipv4From
+   * @param ipv4To
+   * @param direct A direct value of true means that data will not be written to follow via
+   *               the raft protocol, but will be written directly to local disk
+   * @return ErrorOr<nebula::cpp2::ErrorCode, bool>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, bool> replaceHostInPartition(const HostAddr& ipv4From,
                                                                 const HostAddr& ipv4To,
                                                                 bool direct = false);
 
+  /**
+   * @brief Used in BR, after restore meta data, it will replace Zone info from
+   *        current ip to backup ip.
+   *
+   * @param ipv4From
+   * @param ipv4To
+   * @param direct A direct value of true means that data will not be written to follow via
+   *               the raft protocol, but will be written directly to local disk
+   * @return ErrorOr<nebula::cpp2::ErrorCode, bool>
+   */
   ErrorOr<nebula::cpp2::ErrorCode, bool> replaceHostInZone(const HostAddr& ipv4From,
                                                            const HostAddr& ipv4To,
                                                            bool direct = false);
diff --git a/src/meta/processors/admin/AdminClient.cpp b/src/meta/processors/admin/AdminClient.cpp
index 3decaf0b314..5dda012e652 100644
--- a/src/meta/processors/admin/AdminClient.cpp
+++ b/src/meta/processors/admin/AdminClient.cpp
@@ -11,7 +11,6 @@
 #include "common/utils/Utils.h"
 #include "kvstore/Part.h"
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 DEFINE_int32(max_retry_times_admin_op, 30, "max retry times for admin request!");
diff --git a/src/meta/processors/admin/RestoreProcessor.cpp b/src/meta/processors/admin/RestoreProcessor.cpp
index 3f3c35e6cab..acf803b5f2d 100644
--- a/src/meta/processors/admin/RestoreProcessor.cpp
+++ b/src/meta/processors/admin/RestoreProcessor.cpp
@@ -6,7 +6,6 @@
 #include "meta/processors/admin/RestoreProcessor.h"
 
 #include "common/fs/FileUtils.h"
-#include "meta/common/MetaCommon.h"
 
 namespace nebula {
 namespace meta {
diff --git a/src/meta/processors/admin/SnapShot.cpp b/src/meta/processors/admin/SnapShot.cpp
index 49452bd83d5..2b29402d273 100644
--- a/src/meta/processors/admin/SnapShot.cpp
+++ b/src/meta/processors/admin/SnapShot.cpp
@@ -10,7 +10,6 @@
 #include "common/network/NetworkUtils.h"
 #include "common/utils/MetaKeyUtils.h"
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 namespace nebula {
diff --git a/src/meta/processors/config/GetConfigProcessor.cpp b/src/meta/processors/config/GetConfigProcessor.cpp
index 1b1d45fb0d9..47a37da6b6c 100644
--- a/src/meta/processors/config/GetConfigProcessor.cpp
+++ b/src/meta/processors/config/GetConfigProcessor.cpp
@@ -50,8 +50,8 @@ nebula::cpp2::ErrorCode GetConfigProcessor::getOneConfig(const cpp2::ConfigModul
     if (retCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       retCode = nebula::cpp2::ErrorCode::E_CONFIG_NOT_FOUND;
     }
-    LOG(ERROR) << "Get config " << name
-               << " failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Get config " << name
+              << " failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
 
diff --git a/src/meta/processors/config/GetConfigProcessor.h b/src/meta/processors/config/GetConfigProcessor.h
index 398c7f3027f..439ae9f8281 100644
--- a/src/meta/processors/config/GetConfigProcessor.h
+++ b/src/meta/processors/config/GetConfigProcessor.h
@@ -11,6 +11,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Get dynamic configuration by given name in given module(all, meta, graph, storage)
+ *
+ */
 class GetConfigProcessor : public BaseProcessor<cpp2::GetConfigResp> {
  public:
   static GetConfigProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/config/ListConfigsProcessor.cpp b/src/meta/processors/config/ListConfigsProcessor.cpp
index cc7056601c8..788efce778b 100644
--- a/src/meta/processors/config/ListConfigsProcessor.cpp
+++ b/src/meta/processors/config/ListConfigsProcessor.cpp
@@ -15,7 +15,7 @@ void ListConfigsProcessor::process(const cpp2::ListConfigsReq& req) {
   auto iterRet = doPrefix(prefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "List configs failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List configs failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
diff --git a/src/meta/processors/config/ListConfigsProcessor.h b/src/meta/processors/config/ListConfigsProcessor.h
index 9995cfc06a5..0326d6e2817 100644
--- a/src/meta/processors/config/ListConfigsProcessor.h
+++ b/src/meta/processors/config/ListConfigsProcessor.h
@@ -11,6 +11,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief List all registered configs in given module
+ *
+ */
 class ListConfigsProcessor : public BaseProcessor<cpp2::ListConfigsResp> {
  public:
   static ListConfigsProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/config/RegConfigProcessor.cpp b/src/meta/processors/config/RegConfigProcessor.cpp
index 204b805c163..cf70c7321e9 100644
--- a/src/meta/processors/config/RegConfigProcessor.cpp
+++ b/src/meta/processors/config/RegConfigProcessor.cpp
@@ -28,7 +28,7 @@ void RegConfigProcessor::process(const cpp2::RegConfigReq& req) {
       } else {
         auto retCode = nebula::error(configRet);
         if (retCode != nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
-          LOG(ERROR) << "Get config Failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+          LOG(INFO) << "Get config Failed, error: " << apache::thrift::util::enumNameSafe(retCode);
           handleErrorCode(retCode);
           onFinished();
           return;
diff --git a/src/meta/processors/config/RegConfigProcessor.h b/src/meta/processors/config/RegConfigProcessor.h
index 09fe8990f57..40f69ec238d 100644
--- a/src/meta/processors/config/RegConfigProcessor.h
+++ b/src/meta/processors/config/RegConfigProcessor.h
@@ -11,6 +11,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Register configuration in meta service, configuration item could be
+ *        set only after registered.
+ *
+ */
 class RegConfigProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static RegConfigProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/config/SetConfigProcessor.cpp b/src/meta/processors/config/SetConfigProcessor.cpp
index 17b4c3ed971..53a92636d97 100644
--- a/src/meta/processors/config/SetConfigProcessor.cpp
+++ b/src/meta/processors/config/SetConfigProcessor.cpp
@@ -59,8 +59,8 @@ nebula::cpp2::ErrorCode SetConfigProcessor::setConfig(const cpp2::ConfigModule&
     if (retCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       retCode = nebula::cpp2::ErrorCode::E_CONFIG_NOT_FOUND;
     }
-    LOG(ERROR) << "Set config " << name << " failed, error "
-               << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Set config " << name << " failed, error "
+              << apache::thrift::util::enumNameSafe(retCode);
     return retCode;
   }
 
diff --git a/src/meta/processors/config/SetConfigProcessor.h b/src/meta/processors/config/SetConfigProcessor.h
index 7cd8d77e5aa..bd1a60439a8 100644
--- a/src/meta/processors/config/SetConfigProcessor.h
+++ b/src/meta/processors/config/SetConfigProcessor.h
@@ -11,6 +11,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Set configuration of given module's given name,
+ *
+ */
 class SetConfigProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static SetConfigProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/id/GetWorkerIdProcessor.h b/src/meta/processors/id/GetWorkerIdProcessor.h
index 1b1433d81a2..f2db79836f2 100644
--- a/src/meta/processors/id/GetWorkerIdProcessor.h
+++ b/src/meta/processors/id/GetWorkerIdProcessor.h
@@ -11,6 +11,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Assign an incremental work id for each host in cluster, used to
+ *        generate snowflake uuid
+ *
+ */
 class GetWorkerIdProcessor : public BaseProcessor<cpp2::GetWorkerIdResp> {
  public:
   static GetWorkerIdProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/job/BalancePlan.cpp b/src/meta/processors/job/BalancePlan.cpp
index 84ed777e57f..7750fb2945f 100644
--- a/src/meta/processors/job/BalancePlan.cpp
+++ b/src/meta/processors/job/BalancePlan.cpp
@@ -8,7 +8,6 @@
 #include <folly/synchronization/Baton.h>
 
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 DEFINE_uint32(task_concurrency, 10, "The tasks number could be invoked simultaneously");
diff --git a/src/meta/processors/job/JobDescription.cpp b/src/meta/processors/job/JobDescription.cpp
index 2586168dbfd..230da7e7f2e 100644
--- a/src/meta/processors/job/JobDescription.cpp
+++ b/src/meta/processors/job/JobDescription.cpp
@@ -10,8 +10,8 @@
 #include <boost/stacktrace.hpp>
 #include <stdexcept>
 
+#include "common/utils/MetaKeyUtils.h"
 #include "kvstore/KVIterator.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 #include "meta/processors/job/JobUtils.h"
 
diff --git a/src/meta/processors/job/JobExecutor.cpp b/src/meta/processors/job/JobExecutor.cpp
index f8d01f143f6..ec20a1f6602 100644
--- a/src/meta/processors/job/JobExecutor.cpp
+++ b/src/meta/processors/job/JobExecutor.cpp
@@ -10,7 +10,6 @@
 #include "common/utils/Utils.h"
 #include "interface/gen-cpp2/common_types.h"
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 #include "meta/processors/admin/AdminClient.h"
 #include "meta/processors/job/CompactJobExecutor.h"
diff --git a/src/meta/processors/job/JobManager.cpp b/src/meta/processors/job/JobManager.cpp
index 795ade3c73c..fb55c652f5a 100644
--- a/src/meta/processors/job/JobManager.cpp
+++ b/src/meta/processors/job/JobManager.cpp
@@ -18,7 +18,6 @@
 #include "interface/gen-cpp2/common_types.h"
 #include "kvstore/Common.h"
 #include "kvstore/KVIterator.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 #include "meta/processors/admin/AdminClient.h"
 #include "meta/processors/job/BalancePlan.h"
diff --git a/src/meta/processors/job/RebuildJobExecutor.cpp b/src/meta/processors/job/RebuildJobExecutor.cpp
index cd80e043633..8be68da16f9 100644
--- a/src/meta/processors/job/RebuildJobExecutor.cpp
+++ b/src/meta/processors/job/RebuildJobExecutor.cpp
@@ -9,7 +9,6 @@
 #include "common/utils/MetaKeyUtils.h"
 #include "common/utils/Utils.h"
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 DECLARE_int32(heartbeat_interval_secs);
diff --git a/src/meta/processors/job/StatsJobExecutor.cpp b/src/meta/processors/job/StatsJobExecutor.cpp
index ef45e303211..bb918c4f22a 100644
--- a/src/meta/processors/job/StatsJobExecutor.cpp
+++ b/src/meta/processors/job/StatsJobExecutor.cpp
@@ -7,7 +7,6 @@
 
 #include "common/utils/MetaKeyUtils.h"
 #include "common/utils/Utils.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 
 namespace nebula {
diff --git a/src/meta/processors/job/StorageJobExecutor.cpp b/src/meta/processors/job/StorageJobExecutor.cpp
index 14ef50aa4bd..6432b25c423 100644
--- a/src/meta/processors/job/StorageJobExecutor.cpp
+++ b/src/meta/processors/job/StorageJobExecutor.cpp
@@ -10,7 +10,6 @@
 #include "common/utils/Utils.h"
 #include "interface/gen-cpp2/common_types.h"
 #include "meta/ActiveHostsMan.h"
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/Common.h"
 #include "meta/processors/admin/AdminClient.h"
 #include "meta/processors/job/BalanceJobExecutor.h"
diff --git a/src/meta/processors/kv/GetProcessor.cpp b/src/meta/processors/kv/GetProcessor.cpp
deleted file mode 100644
index bed3a344cad..00000000000
--- a/src/meta/processors/kv/GetProcessor.cpp
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/GetProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void GetProcessor::process(const cpp2::GetReq& req) {
-  auto key = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_key());
-  auto result = doGet(key);
-  if (!nebula::ok(result)) {
-    auto retCode = nebula::error(result);
-    LOG(ERROR) << "Get Failed: " << key
-               << " error: " << apache::thrift::util::enumNameSafe(retCode);
-    handleErrorCode(retCode);
-    onFinished();
-    return;
-  }
-
-  handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
-  resp_.value_ref() = std::move(nebula::value(result));
-  onFinished();
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/GetProcessor.h b/src/meta/processors/kv/GetProcessor.h
deleted file mode 100644
index f555044d09e..00000000000
--- a/src/meta/processors/kv/GetProcessor.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_GETPROCESSOR_H_
-#define META_GETPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-class GetProcessor : public BaseProcessor<cpp2::GetResp> {
- public:
-  static GetProcessor* instance(kvstore::KVStore* kvstore) {
-    return new GetProcessor(kvstore);
-  }
-
-  void process(const cpp2::GetReq& req);
-
- private:
-  explicit GetProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::GetResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_GETPROCESSOR_H_
diff --git a/src/meta/processors/kv/MultiGetProcessor.cpp b/src/meta/processors/kv/MultiGetProcessor.cpp
deleted file mode 100644
index ef50ff56337..00000000000
--- a/src/meta/processors/kv/MultiGetProcessor.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/MultiGetProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void MultiGetProcessor::process(const cpp2::MultiGetReq& req) {
-  std::vector<std::string> keys;
-  for (auto& key : req.get_keys()) {
-    keys.emplace_back(MetaKeyUtils::assembleSegmentKey(req.get_segment(), key));
-  }
-
-  auto result = doMultiGet(std::move(keys));
-  if (!nebula::ok(result)) {
-    auto retCode = nebula::error(result);
-    LOG(ERROR) << "MultiGet Failed, error: " << apache::thrift::util::enumNameSafe(retCode);
-    handleErrorCode(retCode);
-    onFinished();
-    return;
-  }
-
-  handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
-  resp_.values_ref() = std::move(nebula::value(result));
-  onFinished();
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/MultiGetProcessor.h b/src/meta/processors/kv/MultiGetProcessor.h
deleted file mode 100644
index d7f06cfd738..00000000000
--- a/src/meta/processors/kv/MultiGetProcessor.h
+++ /dev/null
@@ -1,30 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_MULTIGETPROCESSOR_H_
-#define META_MULTIGETPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-class MultiGetProcessor : public BaseProcessor<cpp2::MultiGetResp> {
- public:
-  static MultiGetProcessor* instance(kvstore::KVStore* kvstore) {
-    return new MultiGetProcessor(kvstore);
-  }
-
-  void process(const cpp2::MultiGetReq& req);
-
- private:
-  explicit MultiGetProcessor(kvstore::KVStore* kvstore)
-      : BaseProcessor<cpp2::MultiGetResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_MULTIGETPROCESSOR_H_
diff --git a/src/meta/processors/kv/MultiPutProcessor.cpp b/src/meta/processors/kv/MultiPutProcessor.cpp
deleted file mode 100644
index 43a655f4d98..00000000000
--- a/src/meta/processors/kv/MultiPutProcessor.cpp
+++ /dev/null
@@ -1,21 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/MultiPutProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void MultiPutProcessor::process(const cpp2::MultiPutReq& req) {
-  CHECK_SEGMENT(req.get_segment());
-  std::vector<kvstore::KV> data;
-  for (auto& pair : req.get_pairs()) {
-    data.emplace_back(MetaKeyUtils::assembleSegmentKey(req.get_segment(), pair.key), pair.value);
-  }
-  doPut(std::move(data));
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/MultiPutProcessor.h b/src/meta/processors/kv/MultiPutProcessor.h
deleted file mode 100644
index 676bcc4f050..00000000000
--- a/src/meta/processors/kv/MultiPutProcessor.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_MULTIPUTPROCESSOR_H_
-#define META_MULTIPUTPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-class MultiPutProcessor : public BaseProcessor<cpp2::ExecResp> {
- public:
-  static MultiPutProcessor* instance(kvstore::KVStore* kvstore) {
-    return new MultiPutProcessor(kvstore);
-  }
-
-  void process(const cpp2::MultiPutReq& req);
-
- private:
-  explicit MultiPutProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_MULTIPUTPROCESSOR_H_
diff --git a/src/meta/processors/kv/RemoveProcessor.cpp b/src/meta/processors/kv/RemoveProcessor.cpp
deleted file mode 100644
index be3c36849d9..00000000000
--- a/src/meta/processors/kv/RemoveProcessor.cpp
+++ /dev/null
@@ -1,18 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/RemoveProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void RemoveProcessor::process(const cpp2::RemoveReq& req) {
-  CHECK_SEGMENT(req.get_segment());
-  auto key = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_key());
-  doRemove(key);
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/RemoveProcessor.h b/src/meta/processors/kv/RemoveProcessor.h
deleted file mode 100644
index 652f79c0dbb..00000000000
--- a/src/meta/processors/kv/RemoveProcessor.h
+++ /dev/null
@@ -1,32 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_REMOVEPROCESSOR_H_
-#define META_REMOVEPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-/**
- * Remove some rows in custom kv operations.
- * */
-class RemoveProcessor : public BaseProcessor<cpp2::ExecResp> {
- public:
-  static RemoveProcessor* instance(kvstore::KVStore* kvstore) {
-    return new RemoveProcessor(kvstore);
-  }
-
-  void process(const cpp2::RemoveReq& req);
-
- private:
-  explicit RemoveProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_DELETEPROCESSOR_H_
diff --git a/src/meta/processors/kv/RemoveRangeProcessor.cpp b/src/meta/processors/kv/RemoveRangeProcessor.cpp
deleted file mode 100644
index 99f6155cb4e..00000000000
--- a/src/meta/processors/kv/RemoveRangeProcessor.cpp
+++ /dev/null
@@ -1,19 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/RemoveRangeProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void RemoveRangeProcessor::process(const cpp2::RemoveRangeReq& req) {
-  CHECK_SEGMENT(req.get_segment());
-  auto start = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_start());
-  auto end = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_end());
-  doRemoveRange(start, end);
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/RemoveRangeProcessor.h b/src/meta/processors/kv/RemoveRangeProcessor.h
deleted file mode 100644
index d6587aac9f6..00000000000
--- a/src/meta/processors/kv/RemoveRangeProcessor.h
+++ /dev/null
@@ -1,30 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_REMOVERANGEPROCESSOR_H_
-#define META_REMOVERANGEPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-class RemoveRangeProcessor : public BaseProcessor<cpp2::ExecResp> {
- public:
-  static RemoveRangeProcessor* instance(kvstore::KVStore* kvstore) {
-    return new RemoveRangeProcessor(kvstore);
-  }
-
-  void process(const cpp2::RemoveRangeReq& req);
-
- private:
-  explicit RemoveRangeProcessor(kvstore::KVStore* kvstore)
-      : BaseProcessor<cpp2::ExecResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_REMOVERANGEPROCESSOR_H_
diff --git a/src/meta/processors/kv/ScanProcessor.cpp b/src/meta/processors/kv/ScanProcessor.cpp
deleted file mode 100644
index 1b14f1a5b8a..00000000000
--- a/src/meta/processors/kv/ScanProcessor.cpp
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#include "meta/processors/kv/ScanProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-void ScanProcessor::process(const cpp2::ScanReq& req) {
-  auto start = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_start());
-  auto end = MetaKeyUtils::assembleSegmentKey(req.get_segment(), req.get_end());
-  auto result = doScan(start, end);
-  if (!nebula::ok(result)) {
-    auto retCode = nebula::error(result);
-    LOG(ERROR) << "Scan Failed, error: " << apache::thrift::util::enumNameSafe(retCode);
-    handleErrorCode(retCode);
-    onFinished();
-    return;
-  }
-
-  handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
-  resp_.values_ref() = std::move(nebula::value(result));
-  onFinished();
-}
-
-}  // namespace meta
-}  // namespace nebula
diff --git a/src/meta/processors/kv/ScanProcessor.h b/src/meta/processors/kv/ScanProcessor.h
deleted file mode 100644
index 1d127af59fb..00000000000
--- a/src/meta/processors/kv/ScanProcessor.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* Copyright (c) 2018 vesoft inc. All rights reserved.
- *
- * This source code is licensed under Apache 2.0 License.
- */
-
-#ifndef META_SCANPROCESSOR_H_
-#define META_SCANPROCESSOR_H_
-
-#include "meta/processors/BaseProcessor.h"
-
-namespace nebula {
-namespace meta {
-
-class ScanProcessor : public BaseProcessor<cpp2::ScanResp> {
- public:
-  static ScanProcessor* instance(kvstore::KVStore* kvstore) {
-    return new ScanProcessor(kvstore);
-  }
-
-  void process(const cpp2::ScanReq& req);
-
- private:
-  explicit ScanProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ScanResp>(kvstore) {}
-};
-
-}  // namespace meta
-}  // namespace nebula
-
-#endif  // META_SCANPROCESSOR_H_
diff --git a/src/meta/processors/listener/ListenerProcessor.cpp b/src/meta/processors/listener/ListenerProcessor.cpp
index 52c6daa90be..36966be8cb9 100644
--- a/src/meta/processors/listener/ListenerProcessor.cpp
+++ b/src/meta/processors/listener/ListenerProcessor.cpp
@@ -21,10 +21,10 @@ void AddListenerProcessor::process(const cpp2::AddListenerReq& req) {
   auto ret = listenerExist(space, type);
   if (ret != nebula::cpp2::ErrorCode::E_LISTENER_NOT_FOUND) {
     if (ret == nebula::cpp2::ErrorCode::SUCCEEDED) {
-      LOG(ERROR) << "Add listener failed, listener already exists.";
+      LOG(INFO) << "Add listener failed, listener already exists.";
       ret = nebula::cpp2::ErrorCode::E_EXISTED;
     } else {
-      LOG(ERROR) << "Add listener failed, error: " << apache::thrift::util::enumNameSafe(ret);
+      LOG(INFO) << "Add listener failed, error: " << apache::thrift::util::enumNameSafe(ret);
     }
     handleErrorCode(ret);
     onFinished();
@@ -38,7 +38,7 @@ void AddListenerProcessor::process(const cpp2::AddListenerReq& req) {
   auto iterRet = doPrefix(prefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "List parts failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List parts failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -65,9 +65,9 @@ void RemoveListenerProcessor::process(const cpp2::RemoveListenerReq& req) {
   auto ret = listenerExist(space, type);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
     if (ret == nebula::cpp2::ErrorCode::E_LISTENER_NOT_FOUND) {
-      LOG(ERROR) << "Remove listener failed, listener not exists.";
+      LOG(INFO) << "Remove listener failed, listener not exists.";
     } else {
-      LOG(ERROR) << "Remove listener failed, error: " << apache::thrift::util::enumNameSafe(ret);
+      LOG(INFO) << "Remove listener failed, error: " << apache::thrift::util::enumNameSafe(ret);
     }
     handleErrorCode(ret);
     onFinished();
@@ -80,7 +80,7 @@ void RemoveListenerProcessor::process(const cpp2::RemoveListenerReq& req) {
   auto iterRet = doPrefix(prefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "Remove listener failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Remove listener failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -102,7 +102,7 @@ void ListListenerProcessor::process(const cpp2::ListListenerReq& req) {
   auto iterRet = doPrefix(prefix);
   if (!nebula::ok(iterRet)) {
     auto retCode = nebula::error(iterRet);
-    LOG(ERROR) << "List listener failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List listener failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
diff --git a/src/meta/processors/listener/ListenerProcessor.h b/src/meta/processors/listener/ListenerProcessor.h
index 78d8ff61062..9606cc8bf0a 100644
--- a/src/meta/processors/listener/ListenerProcessor.h
+++ b/src/meta/processors/listener/ListenerProcessor.h
@@ -11,6 +11,13 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Add typed listeners for given space, assign one listener for each part round robin.
+ *        Notice that in each space, listeners could be only added once now.
+ *        But, of course, you could remove them and re-add new ones.
+ *        It will use heartbeat to instruct the relative storaged to add listeners physically.
+ *
+ */
 class AddListenerProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static AddListenerProcessor* instance(kvstore::KVStore* kvstore) {
@@ -24,6 +31,10 @@ class AddListenerProcessor : public BaseProcessor<cpp2::ExecResp> {
       : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Remove added listener information. Return failed if not found.
+ *
+ */
 class RemoveListenerProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static RemoveListenerProcessor* instance(kvstore::KVStore* kvstore) {
@@ -37,6 +48,11 @@ class RemoveListenerProcessor : public BaseProcessor<cpp2::ExecResp> {
       : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief List all listeners for given spaces and listener type.
+ *        And will fill the listener ative state.
+ *
+ */
 class ListListenerProcessor : public BaseProcessor<cpp2::ListListenerResp> {
  public:
   static ListListenerProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/service/ServiceProcessor.cpp b/src/meta/processors/service/ServiceProcessor.cpp
index bff6ba7aa30..5e3c7efe44c 100644
--- a/src/meta/processors/service/ServiceProcessor.cpp
+++ b/src/meta/processors/service/ServiceProcessor.cpp
@@ -15,15 +15,14 @@ void SignInServiceProcessor::process(const cpp2::SignInServiceReq& req) {
   auto serviceKey = MetaKeyUtils::serviceKey(type);
   auto ret = doGet(serviceKey);
   if (nebula::ok(ret)) {
-    LOG(ERROR) << "Service already exists.";
+    LOG(INFO) << "Service already exists.";
     handleErrorCode(nebula::cpp2::ErrorCode::E_EXISTED);
     onFinished();
     return;
   } else {
     auto retCode = nebula::error(ret);
     if (retCode != nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
-      LOG(ERROR) << "Sign in service failed, error: "
-                 << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Sign in service failed, error: " << apache::thrift::util::enumNameSafe(retCode);
       handleErrorCode(retCode);
       onFinished();
       return;
@@ -44,10 +43,10 @@ void SignOutServiceProcessor::process(const cpp2::SignOutServiceReq& req) {
   if (!nebula::ok(ret)) {
     auto retCode = nebula::error(ret);
     if (retCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
-      LOG(ERROR) << "Sign out service failed, service not exists.";
+      LOG(INFO) << "Sign out service failed, service not exists.";
     } else {
-      LOG(ERROR) << "Sign out service failed, error: "
-                 << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Sign out service failed, error: "
+                << apache::thrift::util::enumNameSafe(retCode);
     }
     handleErrorCode(retCode);
     onFinished();
@@ -66,7 +65,7 @@ void ListServiceClientsProcessor::process(const cpp2::ListServiceClientsReq& req
   auto ret = doGet(serviceKey);
   if (!nebula::ok(ret) && nebula::error(ret) != nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
     auto retCode = nebula::error(ret);
-    LOG(ERROR) << "List service failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List service failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
diff --git a/src/meta/processors/service/ServiceProcessor.h b/src/meta/processors/service/ServiceProcessor.h
index a424381579e..49ce53b6d74 100644
--- a/src/meta/processors/service/ServiceProcessor.h
+++ b/src/meta/processors/service/ServiceProcessor.h
@@ -11,6 +11,11 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Sign in outer service info. It only used in listeners now, such as es
+ *        service info.
+ *
+ */
 class SignInServiceProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static SignInServiceProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/session/SessionManagerProcessor.cpp b/src/meta/processors/session/SessionManagerProcessor.cpp
index 76bb7285b22..bb91bfda288 100644
--- a/src/meta/processors/session/SessionManagerProcessor.cpp
+++ b/src/meta/processors/session/SessionManagerProcessor.cpp
@@ -13,7 +13,7 @@ void CreateSessionProcessor::process(const cpp2::CreateSessionReq& req) {
   const auto& user = req.get_user();
   auto ret = userExist(user);
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "User does not exist, errorCode: " << apache::thrift::util::enumNameSafe(ret);
+    LOG(INFO) << "User does not exist, errorCode: " << apache::thrift::util::enumNameSafe(ret);
     handleErrorCode(ret);
     onFinished();
     return;
@@ -34,8 +34,8 @@ void CreateSessionProcessor::process(const cpp2::CreateSessionReq& req) {
   resp_.session_ref() = session;
   ret = doSyncPut(std::move(data));
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Put data error on meta server, errorCode: "
-               << apache::thrift::util::enumNameSafe(ret);
+    LOG(INFO) << "Put data error on meta server, errorCode: "
+              << apache::thrift::util::enumNameSafe(ret);
   }
   handleErrorCode(ret);
   onFinished();
@@ -53,7 +53,7 @@ void UpdateSessionsProcessor::process(const cpp2::UpdateSessionsReq& req) {
     auto ret = doGet(sessionKey);
     if (!nebula::ok(ret)) {
       auto errCode = nebula::error(ret);
-      LOG(WARNING) << "Session id `" << sessionId << "' not found";
+      LOG(INFO) << "Session id '" << sessionId << "' not found";
       if (errCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
         errCode = nebula::cpp2::ErrorCode::E_SESSION_NOT_FOUND;
       }
@@ -95,8 +95,8 @@ void UpdateSessionsProcessor::process(const cpp2::UpdateSessionsReq& req) {
 
   auto ret = doSyncPut(std::move(data));
   if (ret != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Put data error on meta server, errorCode: "
-               << apache::thrift::util::enumNameSafe(ret);
+    LOG(INFO) << "Put data error on meta server, errorCode: "
+              << apache::thrift::util::enumNameSafe(ret);
     handleErrorCode(ret);
     onFinished();
     return;
@@ -140,7 +140,7 @@ void GetSessionProcessor::process(const cpp2::GetSessionReq& req) {
   auto ret = doGet(sessionKey);
   if (!nebula::ok(ret)) {
     auto errCode = nebula::error(ret);
-    LOG(ERROR) << "Session id `" << sessionId << "' not found";
+    LOG(INFO) << "Session id `" << sessionId << "' not found";
     if (errCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       errCode = nebula::cpp2::ErrorCode::E_SESSION_NOT_FOUND;
     }
@@ -162,7 +162,7 @@ void RemoveSessionProcessor::process(const cpp2::RemoveSessionReq& req) {
   auto ret = doGet(sessionKey);
   if (!nebula::ok(ret)) {
     auto errCode = nebula::error(ret);
-    LOG(ERROR) << "Session id `" << sessionId << "' not found";
+    LOG(INFO) << "Session id `" << sessionId << "' not found";
     if (errCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       errCode = nebula::cpp2::ErrorCode::E_SESSION_NOT_FOUND;
     }
@@ -186,7 +186,7 @@ void KillQueryProcessor::process(const cpp2::KillQueryReq& req) {
     auto ret = doGet(sessionKey);
     if (!nebula::ok(ret)) {
       auto errCode = nebula::error(ret);
-      LOG(ERROR) << "Session id `" << sessionId << "' not found";
+      LOG(INFO) << "Session id `" << sessionId << "' not found";
       if (errCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
         errCode = nebula::cpp2::ErrorCode::E_SESSION_NOT_FOUND;
       }
@@ -211,8 +211,8 @@ void KillQueryProcessor::process(const cpp2::KillQueryReq& req) {
 
   auto putRet = doSyncPut(std::move(data));
   if (putRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Put data error on meta server, errorCode: "
-               << apache::thrift::util::enumNameSafe(putRet);
+    LOG(INFO) << "Put data error on meta server, errorCode: "
+              << apache::thrift::util::enumNameSafe(putRet);
   }
   handleErrorCode(putRet);
   onFinished();
diff --git a/src/meta/processors/session/SessionManagerProcessor.h b/src/meta/processors/session/SessionManagerProcessor.h
index eb69f9ef74b..fd3d70332bd 100644
--- a/src/meta/processors/session/SessionManagerProcessor.h
+++ b/src/meta/processors/session/SessionManagerProcessor.h
@@ -6,12 +6,17 @@
 #ifndef META_SESSIONMANAGERPROCESSOR_H
 #define META_SESSIONMANAGERPROCESSOR_H
 
-#include "meta/common/MetaCommon.h"
 #include "meta/processors/BaseProcessor.h"
 
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Create session and write the session meta data to kv store,
+ *        including graph address and client ip.
+ *        It will check if user exist or not first.
+ *
+ */
 class CreateSessionProcessor : public BaseProcessor<cpp2::CreateSessionResp> {
  public:
   static CreateSessionProcessor* instance(kvstore::KVStore* kvstore) {
@@ -25,6 +30,11 @@ class CreateSessionProcessor : public BaseProcessor<cpp2::CreateSessionResp> {
       : BaseProcessor<cpp2::CreateSessionResp>(kvstore) {}
 };
 
+/**
+ * @brief Update sessions and get killed queries. Then the graph can kill
+ *        its queries by the reponse.
+ *
+ */
 class UpdateSessionsProcessor : public BaseProcessor<cpp2::UpdateSessionsResp> {
  public:
   static UpdateSessionsProcessor* instance(kvstore::KVStore* kvstore) {
@@ -38,6 +48,10 @@ class UpdateSessionsProcessor : public BaseProcessor<cpp2::UpdateSessionsResp> {
       : BaseProcessor<cpp2::UpdateSessionsResp>(kvstore) {}
 };
 
+/**
+ * @brief List all sessions saved in meta kv store.
+ *
+ */
 class ListSessionsProcessor : public BaseProcessor<cpp2::ListSessionsResp> {
  public:
   static ListSessionsProcessor* instance(kvstore::KVStore* kvstore) {
@@ -51,6 +65,10 @@ class ListSessionsProcessor : public BaseProcessor<cpp2::ListSessionsResp> {
       : BaseProcessor<cpp2::ListSessionsResp>(kvstore) {}
 };
 
+/**
+ * @brief Get session by specified session id.
+ *
+ */
 class GetSessionProcessor : public BaseProcessor<cpp2::GetSessionResp> {
  public:
   static GetSessionProcessor* instance(kvstore::KVStore* kvstore) {
@@ -64,6 +82,10 @@ class GetSessionProcessor : public BaseProcessor<cpp2::GetSessionResp> {
       : BaseProcessor<cpp2::GetSessionResp>(kvstore) {}
 };
 
+/**
+ * @brief Remove session by specified session id.
+ *
+ */
 class RemoveSessionProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static RemoveSessionProcessor* instance(kvstore::KVStore* kvstore) {
@@ -77,6 +99,10 @@ class RemoveSessionProcessor : public BaseProcessor<cpp2::ExecResp> {
       : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Mark given queries killed in their sessions.
+ *
+ */
 class KillQueryProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static KillQueryProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/processors/user/AuthenticationProcessor.cpp b/src/meta/processors/user/AuthenticationProcessor.cpp
index ac09be9844c..9185324b6f6 100644
--- a/src/meta/processors/user/AuthenticationProcessor.cpp
+++ b/src/meta/processors/user/AuthenticationProcessor.cpp
@@ -19,18 +19,19 @@ void CreateUserProcessor::process(const cpp2::CreateUserReq& req) {
   if (retCode != nebula::cpp2::ErrorCode::E_USER_NOT_FOUND) {
     if (retCode == nebula::cpp2::ErrorCode::SUCCEEDED) {
       if (!req.get_if_not_exists()) {
-        LOG(ERROR) << "Create User Failed : User " << account << " already existed!";
+        LOG(INFO) << "Create User Failed : User " << account << " already existed!";
         retCode = nebula::cpp2::ErrorCode::E_EXISTED;
       }
     } else {
-      LOG(ERROR) << "Create User Failed : User " << account
-                 << " error: " << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Create User Failed : User " << account
+                << " error: " << apache::thrift::util::enumNameSafe(retCode);
     }
     handleErrorCode(retCode);
     onFinished();
     return;
   }
 
+  LOG(INFO) << "Create User " << account;
   std::vector<kvstore::KV> data;
   data.emplace_back(MetaKeyUtils::userKey(account), MetaKeyUtils::userVal(password));
   doSyncPutAndUpdate(std::move(data));
@@ -49,13 +50,14 @@ void AlterUserProcessor::process(const cpp2::AlterUserReq& req) {
     if (errCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       errCode = nebula::cpp2::ErrorCode::E_USER_NOT_FOUND;
     }
-    LOG(ERROR) << "Get User Failed : User " << account
-               << " error: " << apache::thrift::util::enumNameSafe(errCode);
+    LOG(INFO) << "Get User Failed : User " << account
+              << " error: " << apache::thrift::util::enumNameSafe(errCode);
     handleErrorCode(errCode);
     onFinished();
     return;
   }
 
+  LOG(INFO) << "Alter User " << account;
   std::vector<kvstore::KV> data;
   data.emplace_back(std::move(userKey), std::move(userVal));
   doSyncPutAndUpdate(std::move(data));
@@ -71,11 +73,11 @@ void DropUserProcessor::process(const cpp2::DropUserReq& req) {
       if (req.get_if_exists()) {
         retCode = nebula::cpp2::ErrorCode::SUCCEEDED;
       } else {
-        LOG(ERROR) << "Drop User Failed: " << account << " not found.";
+        LOG(INFO) << "Drop User Failed: " << account << " not found.";
       }
     } else {
-      LOG(ERROR) << "Drop User Failed, User " << account
-                 << " error: " << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Drop User Failed, User " << account
+                << " error: " << apache::thrift::util::enumNameSafe(retCode);
     }
     handleErrorCode(retCode);
     onFinished();
@@ -91,8 +93,8 @@ void DropUserProcessor::process(const cpp2::DropUserReq& req) {
   if (!nebula::ok(iterRet)) {
     retCode = nebula::error(iterRet);
     // The error of prefix is leader change
-    LOG(ERROR) << "Drop User Failed, User " << account
-               << " error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Drop User Failed, User " << account
+              << " error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -130,13 +132,15 @@ void GrantProcessor::process(const cpp2::GrantRoleReq& req) {
   }
   auto retCode = userExist(account);
   if (retCode != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Grant User Failed : User " << account
-               << " error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Grant User Failed : User " << account
+              << " error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
   }
 
+  LOG(INFO) << "Grant User " << account
+            << " role:" << apache::thrift::util::enumNameSafe(roleItem.get_role_type());
   std::vector<kvstore::KV> data;
   data.emplace_back(MetaKeyUtils::roleKey(spaceId, account),
                     MetaKeyUtils::roleVal(roleItem.get_role_type()));
@@ -153,8 +157,8 @@ void RevokeProcessor::process(const cpp2::RevokeRoleReq& req) {
 
   auto userRet = userExist(account);
   if (userRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Revoke User Failed : User " << account
-               << " error: " << apache::thrift::util::enumNameSafe(userRet);
+    LOG(INFO) << "Revoke User Failed : User " << account
+              << " error: " << apache::thrift::util::enumNameSafe(userRet);
     handleErrorCode(userRet);
     onFinished();
     return;
@@ -167,8 +171,8 @@ void RevokeProcessor::process(const cpp2::RevokeRoleReq& req) {
     if (userRet == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       userRet = nebula::cpp2::ErrorCode::E_ROLE_NOT_FOUND;
     }
-    LOG(ERROR) << "Get Role User Failed : User " << account
-               << " error: " << apache::thrift::util::enumNameSafe(userRet);
+    LOG(INFO) << "Get Role User Failed : User " << account
+              << " error: " << apache::thrift::util::enumNameSafe(userRet);
     handleErrorCode(userRet);
     onFinished();
     return;
@@ -176,12 +180,15 @@ void RevokeProcessor::process(const cpp2::RevokeRoleReq& req) {
   auto val = nebula::value(result);
   const auto role = *reinterpret_cast<const cpp2::RoleType*>(val.c_str());
   if (role != roleItem.get_role_type()) {
-    LOG(ERROR) << "Revoke User Failed : User " << account << " error: "
-               << apache::thrift::util::enumNameSafe(nebula::cpp2::ErrorCode::E_IMPROPER_ROLE);
+    LOG(INFO) << "Revoke User Failed : User " << account << " error: "
+              << apache::thrift::util::enumNameSafe(nebula::cpp2::ErrorCode::E_IMPROPER_ROLE);
     handleErrorCode(nebula::cpp2::ErrorCode::E_IMPROPER_ROLE);
     onFinished();
     return;
   }
+
+  LOG(INFO) << "Revoke user " << account
+            << "'s role: " << apache::thrift::util::enumNameSafe(roleItem.get_role_type());
   doSyncMultiRemoveAndUpdate({std::move(roleKey)});
 }
 
@@ -190,8 +197,8 @@ void ChangePasswordProcessor::process(const cpp2::ChangePasswordReq& req) {
   const auto& account = req.get_account();
   auto userRet = userExist(account);
   if (userRet != nebula::cpp2::ErrorCode::SUCCEEDED) {
-    LOG(ERROR) << "Change password Failed, get user " << account << " failed, "
-               << " error: " << apache::thrift::util::enumNameSafe(userRet);
+    LOG(INFO) << "Change password Failed, get user " << account << " failed, "
+              << " error: " << apache::thrift::util::enumNameSafe(userRet);
     handleErrorCode(userRet);
     onFinished();
     return;
@@ -203,8 +210,8 @@ void ChangePasswordProcessor::process(const cpp2::ChangePasswordReq& req) {
     if (retCode == nebula::cpp2::ErrorCode::E_KEY_NOT_FOUND) {
       retCode = nebula::cpp2::ErrorCode::E_USER_NOT_FOUND;
     }
-    LOG(ERROR) << "Get user " << account << " failed, "
-               << " error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Get user " << account << " failed, "
+              << " error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -212,13 +219,14 @@ void ChangePasswordProcessor::process(const cpp2::ChangePasswordReq& req) {
     if (!nebula::value(checkRet)) {
       auto retCode = nebula::cpp2::ErrorCode::E_INVALID_PASSWORD;
       handleErrorCode(retCode);
-      LOG(ERROR) << "Change password failed, user " << account
-                 << apache::thrift::util::enumNameSafe(retCode);
+      LOG(INFO) << "Change password failed, user " << account
+                << apache::thrift::util::enumNameSafe(retCode);
       onFinished();
       return;
     }
   }
 
+  LOG(INFO) << "Change password for user " << account;
   auto userKey = MetaKeyUtils::userKey(account);
   auto userVal = MetaKeyUtils::userVal(req.get_new_encoded_pwd());
   std::vector<kvstore::KV> data;
@@ -229,11 +237,11 @@ void ChangePasswordProcessor::process(const cpp2::ChangePasswordReq& req) {
 void ListUsersProcessor::process(const cpp2::ListUsersReq& req) {
   UNUSED(req);
   folly::SharedMutex::ReadHolder rHolder(LockUtils::userLock());
-  std::string prefix = "__users__";
+  std::string prefix = MetaKeyUtils::userPrefix();
   auto ret = doPrefix(prefix);
   if (!nebula::ok(ret)) {
     auto retCode = nebula::error(ret);
-    LOG(ERROR) << "List User failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List User failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -247,6 +255,8 @@ void ListUsersProcessor::process(const cpp2::ListUsersReq& req) {
     users.emplace(std::move(account), std::move(password));
     iter->next();
   }
+
+  VLOG(2) << "List all users, user count: " << users.size();
   resp_.users_ref() = std::move(users);
   handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
   onFinished();
@@ -261,7 +271,7 @@ void ListRolesProcessor::process(const cpp2::ListRolesReq& req) {
   auto ret = doPrefix(prefix);
   if (!nebula::ok(ret)) {
     auto retCode = nebula::error(ret);
-    LOG(ERROR) << "List roles failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "List roles failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -279,6 +289,8 @@ void ListRolesProcessor::process(const cpp2::ListRolesReq& req) {
     roles.emplace_back(std::move(role));
     iter->next();
   }
+
+  VLOG(2) << "List all user roles for space:" << spaceId << ", user role count: " << roles.size();
   resp_.roles_ref() = std::move(roles);
   handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
   onFinished();
@@ -292,7 +304,7 @@ void GetUserRolesProcessor::process(const cpp2::GetUserRolesReq& req) {
   auto ret = doPrefix(prefix);
   if (!nebula::ok(ret)) {
     auto retCode = nebula::error(ret);
-    LOG(ERROR) << "Prefix roles failed, error: " << apache::thrift::util::enumNameSafe(retCode);
+    LOG(INFO) << "Prefix roles failed, error: " << apache::thrift::util::enumNameSafe(retCode);
     handleErrorCode(retCode);
     onFinished();
     return;
@@ -313,6 +325,8 @@ void GetUserRolesProcessor::process(const cpp2::GetUserRolesReq& req) {
     }
     iter->next();
   }
+
+  VLOG(2) << "Get user:" << act << " roles, its count: " << roles.size();
   resp_.roles_ref() = std::move(roles);
   handleErrorCode(nebula::cpp2::ErrorCode::SUCCEEDED);
   onFinished();
diff --git a/src/meta/processors/user/AuthenticationProcessor.h b/src/meta/processors/user/AuthenticationProcessor.h
index 79fd01a4945..e044982b16a 100644
--- a/src/meta/processors/user/AuthenticationProcessor.h
+++ b/src/meta/processors/user/AuthenticationProcessor.h
@@ -11,6 +11,10 @@
 namespace nebula {
 namespace meta {
 
+/**
+ * @brief Create user with account and password
+ *
+ */
 class CreateUserProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static CreateUserProcessor* instance(kvstore::KVStore* kvstore) {
@@ -24,6 +28,11 @@ class CreateUserProcessor : public BaseProcessor<cpp2::ExecResp> {
       : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Update given user's password, return error if user
+ *        not exist. It will override old password without checking.
+ *
+ */
 class AlterUserProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static AlterUserProcessor* instance(kvstore::KVStore* kvstore) {
@@ -36,6 +45,10 @@ class AlterUserProcessor : public BaseProcessor<cpp2::ExecResp> {
   explicit AlterUserProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Drop user and revoke related roles.
+ *
+ */
 class DropUserProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static DropUserProcessor* instance(kvstore::KVStore* kvstore) {
@@ -48,6 +61,10 @@ class DropUserProcessor : public BaseProcessor<cpp2::ExecResp> {
   explicit DropUserProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Grant user space's given role permission(RoleType:GOD, ADMIN, DBA, USER, GUEST)
+ *
+ */
 class GrantProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static GrantProcessor* instance(kvstore::KVStore* kvstore) {
@@ -60,6 +77,10 @@ class GrantProcessor : public BaseProcessor<cpp2::ExecResp> {
   explicit GrantProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Revoke user's given role. Return error if user or role not exist.
+ *
+ */
 class RevokeProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static RevokeProcessor* instance(kvstore::KVStore* kvstore) {
@@ -72,6 +93,10 @@ class RevokeProcessor : public BaseProcessor<cpp2::ExecResp> {
   explicit RevokeProcessor(kvstore::KVStore* kvstore) : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Change given user's password, but it will check old password first.
+ *
+ */
 class ChangePasswordProcessor : public BaseProcessor<cpp2::ExecResp> {
  public:
   static ChangePasswordProcessor* instance(kvstore::KVStore* kvstore) {
@@ -85,6 +110,10 @@ class ChangePasswordProcessor : public BaseProcessor<cpp2::ExecResp> {
       : BaseProcessor<cpp2::ExecResp>(kvstore) {}
 };
 
+/**
+ * @brief Get all user's accounts and passwords.
+ *
+ */
 class ListUsersProcessor : public BaseProcessor<cpp2::ListUsersResp> {
  public:
   static ListUsersProcessor* instance(kvstore::KVStore* kvstore) {
@@ -98,6 +127,10 @@ class ListUsersProcessor : public BaseProcessor<cpp2::ListUsersResp> {
       : BaseProcessor<cpp2::ListUsersResp>(kvstore) {}
 };
 
+/**
+ * @brief List all user roles granted to given space.
+ *
+ */
 class ListRolesProcessor : public BaseProcessor<cpp2::ListRolesResp> {
  public:
   static ListRolesProcessor* instance(kvstore::KVStore* kvstore) {
@@ -111,6 +144,10 @@ class ListRolesProcessor : public BaseProcessor<cpp2::ListRolesResp> {
       : BaseProcessor<cpp2::ListRolesResp>(kvstore) {}
 };
 
+/**
+ * @brief Get given user's all roles and relative spaces
+ *
+ */
 class GetUserRolesProcessor : public BaseProcessor<cpp2::ListRolesResp> {
  public:
   static GetUserRolesProcessor* instance(kvstore::KVStore* kvstore) {
diff --git a/src/meta/test/ProcessorTest.cpp b/src/meta/test/ProcessorTest.cpp
index 58bce373c42..cb7defb05c9 100644
--- a/src/meta/test/ProcessorTest.cpp
+++ b/src/meta/test/ProcessorTest.cpp
@@ -7,12 +7,6 @@
 #include "common/base/Base.h"
 #include "common/fs/TempDir.h"
 #include "meta/processors/admin/CreateBackupProcessor.h"
-#include "meta/processors/kv/GetProcessor.h"
-#include "meta/processors/kv/MultiGetProcessor.h"
-#include "meta/processors/kv/MultiPutProcessor.h"
-#include "meta/processors/kv/RemoveProcessor.h"
-#include "meta/processors/kv/RemoveRangeProcessor.h"
-#include "meta/processors/kv/ScanProcessor.h"
 #include "meta/processors/parts/AlterSpaceProcessor.h"
 #include "meta/processors/parts/CreateSpaceProcessor.h"
 #include "meta/processors/parts/DropSpaceProcessor.h"
diff --git a/src/meta/upgrade/v1/MetaServiceUtilsV1.h b/src/meta/upgrade/v1/MetaServiceUtilsV1.h
index 189a7dcab25..156df78debb 100644
--- a/src/meta/upgrade/v1/MetaServiceUtilsV1.h
+++ b/src/meta/upgrade/v1/MetaServiceUtilsV1.h
@@ -36,6 +36,11 @@ const std::string kJobArchive = "__job_mgr_archive_";             // NOLINT
 
 using ConfigName = std::pair<cpp2::ConfigModule, std::string>;
 
+/**
+ * @brief Meta kv store utils to help parsing key and values.
+ *        These shoule be used to upgrade meta from 1.x to 2.x
+ *
+ */
 class MetaServiceUtilsV1 final {
  public:
   MetaServiceUtilsV1() = delete;
diff --git a/src/meta/upgrade/v2/MetaServiceUtilsV2.h b/src/meta/upgrade/v2/MetaServiceUtilsV2.h
index 47bf010ce98..7c5cbcec9a2 100644
--- a/src/meta/upgrade/v2/MetaServiceUtilsV2.h
+++ b/src/meta/upgrade/v2/MetaServiceUtilsV2.h
@@ -17,6 +17,11 @@ namespace nebula::meta::v2 {
 
 const std::string kGroupsTable = "__groups__";  // NOLINT
 
+/**
+ * @brief Meta kv store utils to help parsing key and values.
+ *        These shoule be used to upgrade meta from 2.x to 3.x
+ *
+ */
 class MetaServiceUtilsV2 final {
  public:
   MetaServiceUtilsV2() = delete;