[EventEngine] Enable the PosixEventEngine client experiment (#35669)

Closes #35669

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35669 from drfloob:posix-ee-client-flip 0d563ed3a1
PiperOrigin-RevId: 601857289

bazel/experiments.bzl

@@ -217,7 +217,6 @@ EXPERIMENTS = {
                 "v3_compression_filter",
             ],
             "core_end2end_test": [
-                "event_engine_client",
                 "promise_based_server_call",
                 "work_serializer_dispatch",
             ],
@@ -229,9 +228,6 @@ EXPERIMENTS = {
                 "tcp_frame_size_tuning",
                 "tcp_rcv_lowat",
             ],
-            "event_engine_client_test": [
-                "event_engine_client",
-            ],
             "flow_control_test": [
                 "multiping",
                 "peer_state_based_framing",
@@ -259,6 +255,7 @@ EXPERIMENTS = {
         },
         "on": {
             "core_end2end_test": [
+                "event_engine_client",
                 "event_engine_listener",
             ],
             "cpp_lb_end2end_test": [
@@ -266,6 +263,9 @@ EXPERIMENTS = {
                 "round_robin_delegate_to_pick_first",
                 "wrr_delegate_to_pick_first",
             ],
+            "event_engine_client_test": [
+                "event_engine_client",
+            ],
             "event_engine_listener_test": [
                 "event_engine_listener",
             ],

src/core/lib/event_engine/shim.cc

@@ -25,9 +25,10 @@ namespace experimental {
 bool UseEventEngineClient() {
 // TODO(hork, eryu): Adjust the ifdefs accordingly when event engines become
 // available for other platforms.
-#if defined(GRPC_POSIX_SOCKET_TCP) && !defined(GRPC_CFSTREAM)
+#if defined(GRPC_POSIX_SOCKET_TCP) && !defined(GRPC_CFSTREAM) && \
+    !defined(GRPC_DO_NOT_INSTANTIATE_POSIX_POLLER)
   return grpc_core::IsEventEngineClientEnabled();
-#elif defined(GPR_WINDOWS)
+#elif defined(GPR_WINDOWS) && !defined(GRPC_DO_NOT_INSTANTIATE_POSIX_POLLER)
   return grpc_core::IsEventEngineClientEnabled();
 #elif defined(GRPC_IOS_EVENT_ENGINE_CLIENT)
   return true;

src/core/lib/experiments/experiments.cc

@@ -715,7 +715,7 @@ const ExperimentMetadata g_experiment_metadata[] = {
     {"client_privacy", description_client_privacy,
      additional_constraints_client_privacy, nullptr, 0, false, false},
     {"event_engine_client", description_event_engine_client,
-     additional_constraints_event_engine_client, nullptr, 0, false, true},
+     additional_constraints_event_engine_client, nullptr, 0, true, true},
     {"event_engine_dns", description_event_engine_dns,
      additional_constraints_event_engine_dns, nullptr, 0, false, false},
     {"event_engine_listener", description_event_engine_listener,

src/core/lib/experiments/experiments.h

@@ -194,7 +194,8 @@ inline bool IsCanaryClientPrivacyEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_CLIENT_IDLENESS
 inline bool IsClientIdlenessEnabled() { return true; }
 inline bool IsClientPrivacyEnabled() { return false; }
-inline bool IsEventEngineClientEnabled() { return false; }
+#define GRPC_EXPERIMENT_IS_INCLUDED_EVENT_ENGINE_CLIENT
+inline bool IsEventEngineClientEnabled() { return true; }
 inline bool IsEventEngineDnsEnabled() { return false; }
 #define GRPC_EXPERIMENT_IS_INCLUDED_EVENT_ENGINE_LISTENER
 inline bool IsEventEngineListenerEnabled() { return true; }

src/core/lib/experiments/rollouts.yaml

@@ -52,7 +52,7 @@
   default:
     # not tested on iOS at all
     ios: broken
-    posix: false
+    posix: true
     # TODO(hork): resolve when the client end2end test flake rate reduces to
     # a tolerable amount.
     windows: broken

src/python/grpcio_tests/tests/fork/BUILD.bazel

@@ -22,6 +22,8 @@ pyx_library(
 py_test(
     name = "fork_test",
     srcs = glob(["*.py"]),
+    # TODO(yijiem): remove this to test EventEngine fork support
+    env = {"GRPC_EXPERIMENTS": "-event_engine_client"},
     imports = ["../.."],
     main = "_fork_interop_test.py",
     python_version = "PY3",