stats: revert "Prom stats perf improvements" (#27226)

Commit Message: Reverts #24998

See #27173

Additional Description:
Risk Level: n/a
Testing: n/a
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: n/a

source/server/admin/BUILD

@@ -139,18 +139,11 @@ envoy_cc_library(
 
 envoy_cc_library(
     name = "stats_request_lib",
-    srcs = [
-        "grouped_stats_request.cc",
-        "stats_request.cc",
-        "ungrouped_stats_request.cc",
-    ],
-    hdrs = [
-        "grouped_stats_request.h",
-        "stats_request.h",
-        "ungrouped_stats_request.h",
-    ],
+    srcs = ["stats_request.cc"],
+    hdrs = ["stats_request.h"],
     deps = [
         ":handler_ctx_lib",
+        ":prometheus_stats_lib",
         ":stats_params_lib",
         ":stats_render_lib",
         ":utils_lib",
@@ -190,6 +183,7 @@ envoy_cc_library(
     hdrs = ["stats_handler.h"],
     deps = [
         ":handler_ctx_lib",
+        ":prometheus_stats_lib",
         ":stats_render_lib",
         ":stats_request_lib",
         ":utils_lib",
@@ -203,6 +197,19 @@ envoy_cc_library(
     ],
 )
 
+envoy_cc_library(
+    name = "prometheus_stats_lib",
+    srcs = ["prometheus_stats.cc"],
+    hdrs = ["prometheus_stats.h"],
+    deps = [
+        ":stats_params_lib",
+        ":utils_lib",
+        "//envoy/stats:custom_stat_namespaces_interface",
+        "//source/common/buffer:buffer_lib",
+        "//source/common/stats:histogram_lib",
+    ],
+)
+
 envoy_cc_library(
     name = "listeners_handler_lib",
     srcs = ["listeners_handler.cc"],

source/server/admin/admin.cc

@@ -187,7 +187,15 @@ AdminImpl::AdminImpl(const std::string& profile_path, Server::Instance& server,
           makeHandler("/ready", "print server state, return 200 if LIVE, otherwise return 503",
                       MAKE_ADMIN_HANDLER(server_info_handler_.handlerReady), false, false),
           stats_handler_.statsHandler(false /* not active mode */),
-          stats_handler_.prometheusStatsHandler(),
+          makeHandler("/stats/prometheus", "print server stats in prometheus format",
+                      MAKE_ADMIN_HANDLER(stats_handler_.handlerPrometheusStats), false, false,
+                      {{ParamDescriptor::Type::Boolean, "usedonly",
+                        "Only include stats that have been written by system since restart"},
+                       {ParamDescriptor::Type::Boolean, "text_readouts",
+                        "Render text_readouts as new gaugues with value 0 (increases Prometheus "
+                        "data size)"},
+                       {ParamDescriptor::Type::String, "filter",
+                        "Regular expression (Google re2) for filtering stats"}}),
           makeHandler("/stats/recentlookups", "Show recent stat-name lookups",
                       MAKE_ADMIN_HANDLER(stats_handler_.handlerStatsRecentLookups), false, false),
           makeHandler("/stats/recentlookups/clear", "clear list of stat-name lookups and counter",