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/wangle/channel/Handler.h>
20 #include <folly/io/async/EventBase.h>
21 #include <folly/io/async/EventBaseManager.h>
22 #include <folly/io/IOBuf.h>
23 #include <folly/io/IOBufQueue.h>
25 namespace folly { namespace wangle {
28 * OutputBufferingHandler buffers writes in order to minimize syscalls. The
29 * transport will be written to once per event loop instead of on every write.
31 * This handler may only be used in a single Pipeline.
33 class OutputBufferingHandler : public BytesToBytesHandler,
34 protected EventBase::LoopCallback {
36 Future<void> write(Context* ctx, std::unique_ptr<IOBuf> buf) override {
39 return ctx->fireWrite(std::move(buf));
41 // Delay sends to optimize for fewer syscalls
43 DCHECK(!isLoopCallbackScheduled());
44 // Buffer all the sends, and call writev once per event loop.
45 sends_ = std::move(buf);
46 ctx->getTransport()->getEventBase()->runInLoop(this);
48 DCHECK(isLoopCallbackScheduled());
49 sends_->prependChain(std::move(buf));
52 auto f = p.getFuture();
53 promises_.push_back(std::move(p));
58 void runLoopCallback() noexcept override {
59 MoveWrapper<std::vector<Promise<void>>> promises(std::move(promises_));
60 getContext()->fireWrite(std::move(sends_))
61 .then([promises](Try<void> t) mutable {
62 for (auto& p : *promises) {
68 Future<void> close(Context* ctx) override {
69 if (isLoopCallbackScheduled()) {
73 // If there are sends queued, cancel them
74 for (auto& promise : promises_) {
76 folly::make_exception_wrapper<std::runtime_error>(
77 "close() called while sends still pending"));
81 return ctx->fireClose();
84 std::vector<Promise<void>> promises_;
85 std::unique_ptr<IOBuf> sends_{nullptr};
86 bool queueSends_{true};