folly/folly/io/async/AsyncServerSocket.h

/*
 * Copyright (c) Meta Platforms, Inc. and 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.
 */

#pragma once

#include <limits.h>
#include <stddef.h>

#include <chrono>
#include <exception>
#include <functional>
#include <memory>
#include <variant>
#include <vector>

#include <folly/ExceptionWrapper.h>
#include <folly/SocketAddress.h>
#include <folly/String.h>
#include <folly/io/ShutdownSocketSet.h>
#include <folly/io/async/AsyncSocketBase.h>
#include <folly/io/async/AsyncTimeout.h>
#include <folly/io/async/DelayedDestruction.h>
#include <folly/io/async/EventBase.h>
#include <folly/io/async/EventBaseAtomicNotificationQueue.h>
#include <folly/io/async/EventHandler.h>
#include <folly/net/NetOps.h>
#include <folly/net/NetworkSocket.h>
#include <folly/observer/Observer.h>
#include <folly/portability/Sockets.h>

// Due to the way kernel headers are included, this may or may not be defined.
// Number pulled from 3.10 kernel headers.
#ifndef SO_REUSEPORT
#define SO_REUSEPORT …
#endif

#if defined __linux__ && !defined SO_NO_TRANSPARENT_TLS
#define SO_NO_TRANSPARENT_TLS …
#endif

namespace folly {

/**
 * AsyncServerSocket is a listening socket that asynchronously informs a
 * callback whenever a new connection has been accepted.
 *
 * Unlike most async interfaces that always invoke their callback in the same
 * EventBase thread, AsyncServerSocket is unusual in that it can distribute
 * the callbacks across multiple EventBase threads.

 * This supports a common use case for network servers to distribute incoming
 * connections across a number of EventBase threads.  (Servers typically run
 * with one EventBase thread per CPU.)

 * Despite being able to invoke callbacks in multiple EventBase threads,
 * AsyncServerSocket still has one "primary" EventBase.  Operations that
 * modify the AsyncServerSocket state may only be performed from the primary
 * EventBase thread.
 *
 */
class AsyncServerSocket : public DelayedDestruction, public AsyncSocketBase { … };

} // namespace folly