2 * Copyright 2015 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include <folly/futures/SharedPromise.h>
20 #include <folly/wangle/channel/Handler.h>
21 #include <folly/io/async/EventBase.h>
22 #include <folly/io/async/EventBaseManager.h>
23 #include <folly/io/IOBuf.h>
24 #include <folly/io/IOBufQueue.h>
26 namespace folly { namespace wangle {
29 * OutputBufferingHandler buffers writes in order to minimize syscalls. The
30 * transport will be written to once per event loop instead of on every write.
32 * This handler may only be used in a single Pipeline.
34 class OutputBufferingHandler : public OutboundBytesToBytesHandler,
35 protected EventBase::LoopCallback {
37 Future<void> write(Context* ctx, std::unique_ptr<IOBuf> buf) override {
40 return ctx->fireWrite(std::move(buf));
42 // Delay sends to optimize for fewer syscalls
44 DCHECK(!isLoopCallbackScheduled());
45 // Buffer all the sends, and call writev once per event loop.
46 sends_ = std::move(buf);
47 ctx->getTransport()->getEventBase()->runInLoop(this);
49 DCHECK(isLoopCallbackScheduled());
50 sends_->prependChain(std::move(buf));
52 return sharedPromise_.getFuture();
56 void runLoopCallback() noexcept override {
57 MoveWrapper<SharedPromise<void>> sharedPromise;
58 std::swap(*sharedPromise, sharedPromise_);
59 getContext()->fireWrite(std::move(sends_))
60 .then([sharedPromise](Try<void> t) mutable {
61 sharedPromise->setTry(std::move(t));
65 Future<void> close(Context* ctx) override {
66 if (isLoopCallbackScheduled()) {
70 // If there are sends queued, cancel them
71 sharedPromise_.setException(
72 folly::make_exception_wrapper<std::runtime_error>(
73 "close() called while sends still pending"));
75 sharedPromise_ = SharedPromise<void>();
76 return ctx->fireClose();
79 SharedPromise<void> sharedPromise_;
80 std::unique_ptr<IOBuf> sends_{nullptr};
81 bool queueSends_{true};