diff --git a/src/main/java/com/xiaomi/infra/pegasus/client/PegasusClientInterface.java b/src/main/java/com/xiaomi/infra/pegasus/client/PegasusClientInterface.java
index 3af2de70..529580c2 100644
--- a/src/main/java/com/xiaomi/infra/pegasus/client/PegasusClientInterface.java
+++ b/src/main/java/com/xiaomi/infra/pegasus/client/PegasusClientInterface.java
@@ -69,8 +69,8 @@ public PegasusTableInterface openTable(String tableName, int backupRequestDelayM
    *     administrator
    * @param tableOptions control the table feature, such as open backup-request, compress and etc,
    *     see {@link TableOptions}
-   * @return
-   * @throws PException
+   * @return the table handler
+   * @throws PException throws exception if any error occurs.
    */
   public PegasusTableInterface openTable(String tableName, TableOptions tableOptions)
       throws PException;
diff --git a/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ClusterManager.java b/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ClusterManager.java
index 25e9db5e..cc57b78e 100644
--- a/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ClusterManager.java
+++ b/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ClusterManager.java
@@ -48,6 +48,7 @@ public class ClusterManager extends Cluster {
   private ConcurrentHashMap<rpc_address, ReplicaSession> replicaSessions;
   private EventLoopGroup metaGroup; // group used for handle meta logic
   private EventLoopGroup replicaGroup; // group used for handle io with replica servers
+  private EventLoopGroup timeoutTaskGroup; // group used for handle timeout task in replica servers
   private EventLoopGroup tableGroup; // group used for handle table logic
   private String[] metaList;
   private MetaSession metaSession;
@@ -72,6 +73,7 @@ public ClusterManager(ClientOptions opts) throws IllegalArgumentException {
 
     replicaSessions = new ConcurrentHashMap<rpc_address, ReplicaSession>();
     replicaGroup = getEventLoopGroupInstance(opts.getAsyncWorkers());
+    timeoutTaskGroup = getEventLoopGroupInstance(opts.getAsyncWorkers());
     metaGroup = getEventLoopGroupInstance(1);
     tableGroup = getEventLoopGroupInstance(1);
     sessionInterceptorManager = new ReplicaSessionInterceptorManager(opts);
@@ -104,6 +106,7 @@ public ReplicaSession getReplicaSession(rpc_address address) {
           new ReplicaSession(
               address,
               replicaGroup,
+              timeoutTaskGroup,
               max(operationTimeout, ClientOptions.MIN_SOCK_CONNECT_TIMEOUT),
               sessionResetTimeWindowSecs,
               sessionInterceptorManager);
@@ -169,6 +172,7 @@ public void close() {
     Future metaGroupFuture = metaGroup.shutdownGracefully();
     Future replicaGroupFuture = replicaGroup.shutdownGracefully();
     Future tableGroupFuture = tableGroup.shutdownGracefully();
+    Future timeoutTaskGroupFuture = timeoutTaskGroup.shutdownGracefully();
 
     try {
       metaGroupFuture.sync();
@@ -191,6 +195,13 @@ public void close() {
       logger.warn("close table group failed: ", ex);
     }
 
+    try {
+      timeoutTaskGroupFuture.sync();
+      logger.info("timeout task group has closed");
+    } catch (Exception ex) {
+      logger.warn("close timeout task group failed: ", ex);
+    }
+
     logger.info("cluster manager has closed");
   }
 }
diff --git a/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSession.java b/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSession.java
index a8f34e74..66ffaeaf 100644
--- a/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSession.java
+++ b/src/main/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSession.java
@@ -57,11 +57,12 @@ public enum ConnState {
   public ReplicaSession(
       rpc_address address,
       EventLoopGroup rpcGroup,
+      EventLoopGroup timeoutTaskGroup,
       int socketTimeout,
       long sessionResetTimeWindowSec,
       ReplicaSessionInterceptorManager interceptorManager) {
     this.address = address;
-    this.rpcGroup = rpcGroup;
+    this.timeoutTaskGroup = timeoutTaskGroup;
     this.interceptorManager = interceptorManager;
     this.sessionResetTimeWindowMs = sessionResetTimeWindowSec * 1000;
 
@@ -358,7 +359,7 @@ public void operationComplete(ChannelFuture channelFuture) throws Exception {
   // this task will be cancelled.
   // TODO(wutao1): call it addTimeoutTicker
   private ScheduledFuture<?> addTimer(final int seqID, long timeoutInMillseconds) {
-    return rpcGroup.schedule(
+    return this.timeoutTaskGroup.schedule(
         new Runnable() {
           @Override
           public void run() {
@@ -473,7 +474,7 @@ static final class VolatileFields {
 
   private final rpc_address address;
   private Bootstrap boot;
-  private EventLoopGroup rpcGroup;
+  private EventLoopGroup timeoutTaskGroup;
   private ReplicaSessionInterceptorManager interceptorManager;
   private boolean authSucceed;
   final Queue<RequestEntry> authPendingSend = new LinkedList<>();
diff --git a/src/test/java/com/xiaomi/infra/pegasus/client/TestPingZK.java b/src/test/java/com/xiaomi/infra/pegasus/client/TestPingZK.java
index ead83468..98b3b4a5 100644
--- a/src/test/java/com/xiaomi/infra/pegasus/client/TestPingZK.java
+++ b/src/test/java/com/xiaomi/infra/pegasus/client/TestPingZK.java
@@ -37,7 +37,7 @@ public void testPingZK() throws PException {
     System.out.println("write config to " + configPath);
     zkClient.writeData(zkPath, configData.getBytes());
 
-    PegasusClientInterface client = PegasusClientFactory.getSingletonClient(configPath);
+    PegasusClientInterface client = PegasusClientFactory.createClient(configPath);
     String tableName = "temp";
 
     byte[] hashKey = "hello".getBytes();
diff --git a/src/test/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSessionTest.java b/src/test/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSessionTest.java
index 155a6180..4fd1cb14 100644
--- a/src/test/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSessionTest.java
+++ b/src/test/java/com/xiaomi/infra/pegasus/rpc/async/ReplicaSessionTest.java
@@ -295,8 +295,10 @@ public void testSessionConnectTimeout() throws InterruptedException {
 
     long start = System.currentTimeMillis();
     EventLoopGroup rpcGroup = new NioEventLoopGroup(4);
+    EventLoopGroup timeoutTaskGroup = new NioEventLoopGroup(4);
     ReplicaSession rs =
-        new ReplicaSession(addr, rpcGroup, 1000, 30, (ReplicaSessionInterceptorManager) null);
+        new ReplicaSession(
+            addr, rpcGroup, timeoutTaskGroup, 1000, 30, (ReplicaSessionInterceptorManager) null);
     rs.tryConnect().awaitUninterruptibly();
     long end = System.currentTimeMillis();
     Assert.assertEquals((end - start) / 1000, 1); // ensure connect failed within 1sec