tcp: switching to the new pool (envoyproxy#12180)

Risk Level: High (roll back first, ask questions later)
Testing: cloned all unit tests and all integration tests.
Docs Changes: n/a
Release Notes: inline
Runtime guard: envoy.reloadable_features.new_tcp_connection_pool

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

docs/root/version_history/current.rst

@@ -42,6 +42,7 @@ New Features
 * load balancer: added a :ref:`configuration<envoy_v3_api_msg_config.cluster.v3.Cluster.LeastRequestLbConfig>` option to specify the active request bias used by the least request load balancer.
 * redis: added fault injection support :ref:`fault injection for redis proxy <envoy_v3_api_field_extensions.filters.network.redis_proxy.v3.RedisProxy.faults>`, described further in :ref:`configuration documentation <config_network_filters_redis_proxy>`.
 * tap: added :ref:`generic body matcher<envoy_v3_api_msg_config.tap.v3.HttpGenericBodyMatch>` to scan http requests and responses for text or hex patterns.
+* tcp: switched the TCP connection pool to the new "shared" connection pool, sharing a common code base with HTTP and HTTP/2. Any unexpected behavioral changes can be temporarily reverted by setting `envoy.reloadable_features.new_tcp_connection_pool` to false.
 
 Deprecated
 ----------

source/common/runtime/runtime_features.cc

@@ -71,6 +71,7 @@ constexpr const char* runtime_features[] = {
     "envoy.reloadable_features.http_default_alpn",
     "envoy.reloadable_features.listener_in_place_filterchain_update",
     "envoy.reloadable_features.new_codec_behavior",
+    "envoy.reloadable_features.new_tcp_connection_pool",
     "envoy.reloadable_features.preserve_query_string_in_path_redirects",
     "envoy.reloadable_features.preserve_upstream_date",
     "envoy.reloadable_features.stop_faking_paths",
@@ -87,8 +88,6 @@ constexpr const char* runtime_features[] = {
 // When features are added here, there should be a tracking bug assigned to the
 // code owner to flip the default after sufficient testing.
 constexpr const char* disabled_runtime_features[] = {
-    // TODO(alyssawilk) flip true after the release.
-    "envoy.reloadable_features.new_tcp_connection_pool",
     // Sentinel and test flag.
     "envoy.reloadable_features.test_feature_false",
 };