Cache python-import in getExecutor

Summary: [Folly] Cache python-import in `getExecutor` so that it happens only once overall rather than once per call.

Reviewed By: nanshu

Differential Revision: D23657508

fbshipit-source-id: 06d3bd53303cac9c10fff74f4e6daaeccdc59471

CMakeLists.txt

@@ -158,11 +158,13 @@ REMOVE_MATCHES_FROM_LISTS(files hfiles
 list(REMOVE_ITEM files
   ${FOLLY_DIR}/experimental/JSONSchemaTester.cpp
   ${FOLLY_DIR}/experimental/io/HugePageUtil.cpp
+  ${FOLLY_DIR}/python/executor.cpp
   ${FOLLY_DIR}/python/fibers.cpp
   ${FOLLY_DIR}/python/GILAwareManualExecutor.cpp
   ${FOLLY_DIR}/cybld/folly/executor.cpp
 )
 list(REMOVE_ITEM hfiles
+  ${FOLLY_DIR}/python/executor.h
   ${FOLLY_DIR}/python/fibers.h
   ${FOLLY_DIR}/python/GILAwareManualExecutor.h
 )

folly/python/executor.cpp

+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <folly/python/executor.h>
+
+#include <stdexcept>
+
+#include <folly/CppAttributes.h>
+#include <folly/python/AsyncioExecutor.h>
+#include <folly/python/executor_api.h> // @manual
+
+namespace folly {
+namespace python {
+
+namespace {
+
+void do_import() {
+  if (0 != import_folly__executor()) {
+    throw std::runtime_error("import_folly__executor failed");
+  }
+}
+
+} // namespace
+
+folly::Executor* getExecutor() {
+  FOLLY_MAYBE_UNUSED static bool done = (do_import(), false);
+  return get_executor();
+}
+
+} // namespace python
+} // namespace folly

folly/python/executor.h

@@ -16,15 +16,12 @@
 
 #pragma once
 
-#include <folly/python/executor_api.h> // @manual
+#include <folly/Executor.h>
 
 namespace folly {
 namespace python {
 
-inline folly::Executor* getExecutor() {
-  import_folly__executor();
-  return get_executor();
-}
+folly::Executor* getExecutor();
 
 } // namespace python
 } // namespace folly