[EventEngine] Always initialize PosixEventEngine when created. (#32724)

If an engine is created, it should be fully functional regardless of
whether gRPC-core experiments are on or off. The trade-off for now is
that when the core experiments are not enabled, the engine will be
slowly polling with nothing to do.

---------

Co-authored-by: drfloob <drfloob@users.noreply.github.com>

src/core/BUILD

@@ -1931,7 +1931,6 @@ grpc_cc_library(
     deps = [
         "event_engine_common",
         "event_engine_poller",
-        "event_engine_shim",
         "event_engine_tcp_socket_utils",
         "event_engine_thread_pool",
         "event_engine_trace",

src/core/lib/event_engine/posix_engine/posix_engine.cc

@@ -41,7 +41,6 @@
 #include "src/core/lib/event_engine/posix.h"
 #include "src/core/lib/event_engine/posix_engine/tcp_socket_utils.h"
 #include "src/core/lib/event_engine/posix_engine/timer.h"
-#include "src/core/lib/event_engine/shim.h"
 #include "src/core/lib/event_engine/tcp_socket_utils.h"
 #include "src/core/lib/event_engine/trace.h"
 #include "src/core/lib/event_engine/utils.h"
@@ -66,10 +65,6 @@ using namespace std::chrono_literals;
 namespace grpc_event_engine {
 namespace experimental {
 
-bool NeedPosixEngine() {
-  return UseEventEngineClient() || UseEventEngineListener();
-}
-
 #ifdef GRPC_POSIX_SOCKET_TCP
 
 void AsyncConnect::Start(EventEngine::Duration timeout) {
@@ -340,24 +335,20 @@ PosixEventEngine::PosixEventEngine(PosixEventPoller* poller)
     : connection_shards_(std::max(2 * gpr_cpu_num_cores(), 1u)),
       executor_(std::make_shared<ThreadPool>()),
       timer_manager_(executor_) {
-  if (NeedPosixEngine()) {
-    poller_manager_ = std::make_shared<PosixEnginePollerManager>(poller);
-  }
+  poller_manager_ = std::make_shared<PosixEnginePollerManager>(poller);
 }
 
 PosixEventEngine::PosixEventEngine()
     : connection_shards_(std::max(2 * gpr_cpu_num_cores(), 1u)),
       executor_(std::make_shared<ThreadPool>()),
       timer_manager_(executor_) {
-  if (NeedPosixEngine()) {
-    poller_manager_ = std::make_shared<PosixEnginePollerManager>(executor_);
-    // The threadpool must be instantiated after the poller otherwise, the
-    // process will deadlock when forking.
-    if (poller_manager_->Poller() != nullptr) {
-      executor_->Run([poller_manager = poller_manager_]() {
-        PollerWorkInternal(poller_manager);
-      });
-    }
+  poller_manager_ = std::make_shared<PosixEnginePollerManager>(executor_);
+  // The threadpool must be instantiated after the poller otherwise, the
+  // process will deadlock when forking.
+  if (poller_manager_->Poller() != nullptr) {
+    executor_->Run([poller_manager = poller_manager_]() {
+      PollerWorkInternal(poller_manager);
+    });
   }
 }
 
@@ -549,9 +540,6 @@ EventEngine::ConnectionHandle PosixEventEngine::Connect(
     OnConnectCallback on_connect, const ResolvedAddress& addr,
     const EndpointConfig& args, MemoryAllocator memory_allocator,
     Duration timeout) {
-  if (!NeedPosixEngine()) {
-    grpc_core::Crash("unimplemented");
-  }
 #ifdef GRPC_POSIX_SOCKET_TCP
   GPR_ASSERT(poller_manager_ != nullptr);
   PosixTcpOptions options = TcpOptionsFromEndpointConfig(args);
@@ -574,9 +562,6 @@ std::unique_ptr<PosixEndpointWithFdSupport>
 PosixEventEngine::CreatePosixEndpointFromFd(int fd,
                                             const EndpointConfig& config,
                                             MemoryAllocator memory_allocator) {
-  if (!NeedPosixEngine()) {
-    grpc_core::Crash("unimplemented");
-  }
 #ifdef GRPC_POSIX_SOCKET_TCP
   GPR_DEBUG_ASSERT(fd > 0);
   PosixEventPoller* poller = poller_manager_->Poller();
@@ -623,9 +608,6 @@ PosixEventEngine::CreatePosixListener(
     absl::AnyInvocable<void(absl::Status)> on_shutdown,
     const EndpointConfig& config,
     std::unique_ptr<MemoryAllocatorFactory> memory_allocator_factory) {
-  if (!NeedPosixEngine()) {
-    grpc_core::Crash("unimplemented");
-  }
 #ifdef GRPC_POSIX_SOCKET_TCP
   return std::make_unique<PosixEngineListener>(
       std::move(on_accept), std::move(on_shutdown), config,

test/core/event_engine/posix/posix_event_engine_connect_test.cc

@@ -44,7 +44,6 @@
 #include "src/core/lib/event_engine/channel_args_endpoint_config.h"
 #include "src/core/lib/event_engine/posix_engine/posix_engine.h"
 #include "src/core/lib/event_engine/tcp_socket_utils.h"
-#include "src/core/lib/experiments/config.h"
 #include "src/core/lib/gprpp/crash.h"
 #include "src/core/lib/gprpp/notification.h"
 #include "src/core/lib/resource_quota/memory_quota.h"
@@ -209,8 +208,6 @@ TEST(PosixEventEngineTest, IndefiniteConnectCancellationTest) {
 int main(int argc, char** argv) {
   grpc::testing::TestEnvironment env(&argc, argv);
   ::testing::InitGoogleTest(&argc, argv);
-  // TODO(vigneshbabu): remove when the experiment is over
-  grpc_core::ForceEnableExperiment("event_engine_client", true);
   grpc_init();
   int ret = RUN_ALL_TESTS();
   grpc_shutdown();

test/core/event_engine/test_suite/posix_event_engine_test.cc

@@ -18,7 +18,6 @@
 #include <grpc/grpc.h>
 
 #include "src/core/lib/event_engine/posix_engine/posix_engine.h"
-#include "src/core/lib/experiments/config.h"
 #include "test/core/event_engine/test_suite/event_engine_test_framework.h"
 #include "test/core/event_engine/test_suite/posix/oracle_event_engine_posix.h"
 #include "test/core/event_engine/test_suite/tests/client_test.h"
@@ -41,9 +40,6 @@ int main(int argc, char** argv) {
   grpc_event_engine::experimental::InitTimerTests();
   grpc_event_engine::experimental::InitClientTests();
   grpc_event_engine::experimental::InitServerTests();
-  // TODO(vigneshbabu): remove when the experiment is over
-  grpc_core::ForceEnableExperiment("event_engine_client", true);
-  grpc_core::ForceEnableExperiment("event_engine_listener", true);
   // TODO(ctiller): EventEngine temporarily needs grpc to be initialized first
   // until we clear out the iomgr shutdown code.
   grpc_init();

test/core/event_engine/test_suite/thready_posix_event_engine_test.cc

@@ -18,7 +18,6 @@
 #include <grpc/grpc.h>
 
 #include "src/core/lib/event_engine/posix_engine/posix_engine.h"
-#include "src/core/lib/experiments/config.h"
 #include "test/core/event_engine/test_suite/event_engine_test_framework.h"
 #include "test/core/event_engine/test_suite/posix/oracle_event_engine_posix.h"
 #include "test/core/event_engine/test_suite/tests/client_test.h"
@@ -46,9 +45,6 @@ int main(int argc, char** argv) {
   grpc_event_engine::experimental::InitTimerTests();
   grpc_event_engine::experimental::InitClientTests();
   grpc_event_engine::experimental::InitServerTests();
-  // TODO(vigneshbabu): remove when the experiment is over
-  grpc_core::ForceEnableExperiment("event_engine_client", true);
-  grpc_core::ForceEnableExperiment("event_engine_listener", true);
   // TODO(ctiller): EventEngine temporarily needs grpc to be initialized first
   // until we clear out the iomgr shutdown code.
   grpc_init();