FiberManager - addFiberFuture and blockingWait

Summary:
This diff has two goals:
- To provide an API that allows users to schedule async annotated functors to run on fibers (thereby removing the need to use `init_await` at the top of the stack)
- To provide a boilerplate-free entry point into fiber code that should work for a majority of testing/benchmarking interactions with fiber manager.

The diff implements two APIs:
-addFiberFuture: wrapper around `fiberManager.addTaskFuture`. The differing name is to mainly avoid namespace collisions and avoid confusion with `coro::Task`
- blockingWait: Fiber entry point helper

Reviewed By: A5he

Differential Revision: D22071005

fbshipit-source-id: 24ceea005d32f6e2c84b4599042703207504bd0f

folly/fibers/async/FiberManager.h

+/*
+ * 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/fibers/FiberManager.h>
+#include <folly/fibers/async/Async.h>
+
+#pragma once
+
+namespace folly {
+namespace fibers {
+namespace async {
+
+namespace detail {
+/**
+ * Schedule an async-annotated functor to run on a fiber manager. Returns a
+ * future for the result.
+ *
+ * In most cases, you probably want to use executeOnFiberAndWait instead
+ */
+template <typename F>
+auto addFiberFuture(F&& func, FiberManager& fm) {
+  return fm.addTaskFuture(
+      [func = std::forward<F>(func)] { return init_await(func()); });
+}
+} // namespace detail
+
+} // namespace async
+} // namespace fibers
+} // namespace folly

folly/fibers/async/WaitUtils.h

+/*
+ * 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/fibers/FiberManagerInternal.h>
+#include <folly/fibers/FiberManagerMap.h>
+#include <folly/fibers/async/Async.h>
+#include <folly/fibers/async/FiberManager.h>
+
+#pragma once
+
+namespace folly {
+namespace fibers {
+namespace async {
+
+namespace detail {
+template <typename F>
+auto executeOnFiberAndWait(F&& func, folly::EventBase& evb, FiberManager& fm) {
+  DCHECK(!detail::onFiber());
+  return addFiberFuture(std::forward<F>(func), fm).getVia(&evb);
+}
+} // namespace detail
+
+/**
+ * Run an async-annotated functor `func`, to completion on a fiber manager `fm`
+ * associated with Event Base `evb`, blocking the current thread.
+ *
+ * Should not be called from fiber context.
+ *
+ * Several overloads are provided to configure the executor / fiber manager
+ * options
+ */
+template <typename F>
+auto executeOnFiberAndWait(
+    F&& func,
+    const FiberManager::Options& opts = FiberManager::Options()) {
+  folly::EventBase evb;
+  return detail::executeOnFiberAndWait(
+      std::forward<F>(func), evb, getFiberManager(evb, opts));
+}
+
+template <typename F>
+auto executeOnFiberAndWait(F&& func, const FiberManager::FrozenOptions& opts) {
+  folly::EventBase evb;
+  return detail::executeOnFiberAndWait(
+      std::forward<F>(func), evb, getFiberManager(evb, opts));
+}
+
+template <typename F>
+auto executeOnFiberAndWait(
+    F&& func,
+    folly::EventBase& evb,
+    const FiberManager::Options& opts = FiberManager::Options()) {
+  return detail::executeOnFiberAndWait(
+      std::forward<F>(func), evb, getFiberManager(evb, opts));
+}
+
+template <typename F>
+auto executeOnFiberAndWait(
+    F&& func,
+    folly::EventBase& evb,
+    const FiberManager::FrozenOptions& opts) {
+  return detail::executeOnFiberAndWait(
+      std::forward<F>(func), evb, getFiberManager(evb, opts));
+}
+
+} // namespace async
+} // namespace fibers
+} // namespace folly

folly/fibers/async/test/AsyncTest.cpp

@@ -20,8 +20,10 @@
 #include <folly/fibers/FiberManagerMap.h>
 #include <folly/fibers/async/Async.h>
 #include <folly/fibers/async/Baton.h>
+#include <folly/fibers/async/FiberManager.h>
 #include <folly/fibers/async/Future.h>
 #include <folly/fibers/async/Promise.h>
+#include <folly/fibers/async/WaitUtils.h>
 #include <folly/io/async/EventBase.h>
 
 #if FOLLY_HAS_COROUTINES
@@ -238,3 +240,27 @@ TEST(AsyncTest, asyncConstructorGuides) {
       std::is_same<int&, async::async_inner_type_t<decltype(getRef())>>::value);
 }
 #endif
+
+TEST(FiberManager, asyncFiberManager) {
+  {
+    folly::EventBase evb;
+    bool completed = false;
+    async::detail::addFiberFuture(
+        [&]() -> async::Async<void> {
+          completed = true;
+          return {};
+        },
+        getFiberManager(evb))
+        .getVia(&evb);
+    EXPECT_TRUE(completed);
+  }
+
+  {
+    bool completed = false;
+    async::executeOnFiberAndWait([&]() -> async::Async<void> {
+      completed = true;
+      return {};
+    });
+    EXPECT_TRUE(completed);
+  }
+}