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/io/async/DelayedDestruction.h>
20 #include <folly/io/async/EventHandler.h>
21 #include <folly/io/async/EventBase.h>
22 #include <folly/io/async/NotificationQueue.h>
23 #include <folly/io/async/AsyncTimeout.h>
24 #include <folly/io/ShutdownSocketSet.h>
25 #include <folly/SocketAddress.h>
31 #include <sys/socket.h>
34 // Due to the way kernel headers are included, this may or may not be defined.
35 // Number pulled from 3.10 kernel headers.
37 #define SO_REUSEPORT 15
43 * A listening socket that asynchronously informs a callback whenever a new
44 * connection has been accepted.
46 * Unlike most async interfaces that always invoke their callback in the same
47 * EventBase thread, AsyncServerSocket is unusual in that it can distribute
48 * the callbacks across multiple EventBase threads.
50 * This supports a common use case for network servers to distribute incoming
51 * connections across a number of EventBase threads. (Servers typically run
52 * with one EventBase thread per CPU.)
54 * Despite being able to invoke callbacks in multiple EventBase threads,
55 * AsyncServerSocket still has one "primary" EventBase. Operations that
56 * modify the AsyncServerSocket state may only be performed from the primary
59 class AsyncServerSocket : public DelayedDestruction {
61 typedef std::unique_ptr<AsyncServerSocket, Destructor> UniquePtr;
62 // Disallow copy, move, and default construction.
63 AsyncServerSocket(AsyncServerSocket&&) = delete;
65 class AcceptCallback {
67 virtual ~AcceptCallback() {}
70 * connectionAccepted() is called whenever a new client connection is
73 * The AcceptCallback will remain installed after connectionAccepted()
76 * @param fd The newly accepted client socket. The AcceptCallback
77 * assumes ownership of this socket, and is responsible
78 * for closing it when done. The newly accepted file
79 * descriptor will have already been put into
81 * @param clientAddr A reference to a TSocketAddress struct containing the
82 * client's address. This struct is only guaranteed to
83 * remain valid until connectionAccepted() returns.
85 virtual void connectionAccepted(int fd,
86 const SocketAddress& clientAddr)
90 * acceptError() is called if an error occurs while accepting.
92 * The AcceptCallback will remain installed even after an accept error,
93 * as the errors are typically somewhat transient, such as being out of
94 * file descriptors. The server socket must be explicitly stopped if you
95 * wish to stop accepting after an error.
97 * @param ex An exception representing the error.
99 virtual void acceptError(const std::exception& ex) noexcept = 0;
102 * acceptStarted() will be called in the callback's EventBase thread
103 * after this callback has been added to the AsyncServerSocket.
105 * acceptStarted() will be called before any calls to connectionAccepted()
106 * or acceptError() are made on this callback.
108 * acceptStarted() makes it easier for callbacks to perform initialization
109 * inside the callback thread. (The call to addAcceptCallback() must
110 * always be made from the AsyncServerSocket's primary EventBase thread.
111 * acceptStarted() provides a hook that will always be invoked in the
112 * callback's thread.)
114 * Note that the call to acceptStarted() is made once the callback is
115 * added, regardless of whether or not the AsyncServerSocket is actually
116 * accepting at the moment. acceptStarted() will be called even if the
117 * AsyncServerSocket is paused when the callback is added (including if
118 * the initial call to startAccepting() on the AsyncServerSocket has not
121 virtual void acceptStarted() noexcept {}
124 * acceptStopped() will be called when this AcceptCallback is removed from
125 * the AsyncServerSocket, or when the AsyncServerSocket is destroyed,
126 * whichever occurs first.
128 * No more calls to connectionAccepted() or acceptError() will be made
129 * after acceptStopped() is invoked.
131 virtual void acceptStopped() noexcept {}
134 static const uint32_t kDefaultMaxAcceptAtOnce = 30;
135 static const uint32_t kDefaultCallbackAcceptAtOnce = 5;
136 static const uint32_t kDefaultMaxMessagesInQueue = 0;
138 * Create a new AsyncServerSocket with the specified EventBase.
140 * @param eventBase The EventBase to use for driving the asynchronous I/O.
141 * If this parameter is nullptr, attachEventBase() must be
142 * called before this socket can begin accepting
145 explicit AsyncServerSocket(EventBase* eventBase = nullptr);
148 * Helper function to create a shared_ptr<AsyncServerSocket>.
150 * This passes in the correct destructor object, since AsyncServerSocket's
151 * destructor is protected and cannot be invoked directly.
153 static std::shared_ptr<AsyncServerSocket>
154 newSocket(EventBase* evb = nullptr) {
155 return std::shared_ptr<AsyncServerSocket>(new AsyncServerSocket(evb),
159 void setShutdownSocketSet(ShutdownSocketSet* newSS);
162 * Destroy the socket.
164 * AsyncServerSocket::destroy() must be called to destroy the socket.
165 * The normal destructor is private, and should not be invoked directly.
166 * This prevents callers from deleting a AsyncServerSocket while it is
167 * invoking a callback.
169 * destroy() must be invoked from the socket's primary EventBase thread.
171 * If there are AcceptCallbacks still installed when destroy() is called,
172 * acceptStopped() will be called on these callbacks to notify them that
173 * accepting has stopped. Accept callbacks being driven by other EventBase
174 * threads may continue to receive new accept callbacks for a brief period of
175 * time after destroy() returns. They will not receive any more callback
176 * invocations once acceptStopped() is invoked.
178 virtual void destroy();
181 * Attach this AsyncServerSocket to its primary EventBase.
183 * This may only be called if the AsyncServerSocket is not already attached
184 * to a EventBase. The AsyncServerSocket must be attached to a EventBase
185 * before it can begin accepting connections.
187 void attachEventBase(EventBase *eventBase);
190 * Detach the AsyncServerSocket from its primary EventBase.
192 * detachEventBase() may only be called if the AsyncServerSocket is not
193 * currently accepting connections.
195 void detachEventBase();
198 * Get the EventBase used by this socket.
200 EventBase* getEventBase() const {
205 * Create a AsyncServerSocket from an existing socket file descriptor.
207 * useExistingSocket() will cause the AsyncServerSocket to take ownership of
208 * the specified file descriptor, and use it to listen for new connections.
209 * The AsyncServerSocket will close the file descriptor when it is
212 * useExistingSocket() must be called before bind() or listen().
214 * The supplied file descriptor will automatically be put into non-blocking
215 * mode. The caller may have already directly called bind() and possibly
216 * listen on the file descriptor. If so the caller should skip calling the
217 * corresponding AsyncServerSocket::bind() and listen() methods.
219 * On error a TTransportException will be thrown and the caller will retain
220 * ownership of the file descriptor.
222 void useExistingSocket(int fd);
223 void useExistingSockets(const std::vector<int>& fds);
226 * Return the underlying file descriptor
228 std::vector<int> getSockets() const {
229 std::vector<int> sockets;
230 for (auto& handler : sockets_) {
231 sockets.push_back(handler.socket_);
237 * Backwards compatible getSocket, warns if > 1 socket
239 int getSocket() const {
240 if (sockets_.size() > 1) {
241 VLOG(2) << "Warning: getSocket can return multiple fds, " <<
242 "but getSockets was not called, so only returning the first";
244 if (sockets_.size() == 0) {
247 return sockets_[0].socket_;
252 * Bind to the specified address.
254 * This must be called from the primary EventBase thread.
256 * Throws TTransportException on error.
258 virtual void bind(const SocketAddress& address);
261 * Bind to the specified port for the specified addresses.
263 * This must be called from the primary EventBase thread.
265 * Throws TTransportException on error.
268 const std::vector<IPAddress>& ipAddresses,
272 * Bind to the specified port.
274 * This must be called from the primary EventBase thread.
276 * Throws TTransportException on error.
278 virtual void bind(uint16_t port);
281 * Get the local address to which the socket is bound.
283 * Throws TTransportException on error.
285 void getAddress(SocketAddress* addressReturn) const;
288 * Get all the local addresses to which the socket is bound.
290 * Throws TTransportException on error.
292 std::vector<SocketAddress> getAddresses() const;
295 * Begin listening for connections.
297 * This calls ::listen() with the specified backlog.
299 * Once listen() is invoked the socket will actually be open so that remote
300 * clients may establish connections. (Clients that attempt to connect
301 * before listen() is called will receive a connection refused error.)
303 * At least one callback must be set and startAccepting() must be called to
304 * actually begin notifying the accept callbacks of newly accepted
305 * connections. The backlog parameter controls how many connections the
306 * kernel will accept and buffer internally while the accept callbacks are
307 * paused (or if accepting is enabled but the callbacks cannot keep up).
309 * bind() must be called before calling listen().
310 * listen() must be called from the primary EventBase thread.
312 * Throws TTransportException on error.
314 virtual void listen(int backlog);
317 * Add an AcceptCallback.
319 * When a new socket is accepted, one of the AcceptCallbacks will be invoked
320 * with the new socket. The AcceptCallbacks are invoked in a round-robin
321 * fashion. This allows the accepted sockets to distributed among a pool of
322 * threads, each running its own EventBase object. This is a common model,
323 * since most asynchronous-style servers typically run one EventBase thread
326 * The EventBase object associated with each AcceptCallback must be running
327 * its loop. If the EventBase loop is not running, sockets will still be
328 * scheduled for the callback, but the callback cannot actually get invoked
329 * until the loop runs.
331 * This method must be invoked from the AsyncServerSocket's primary
334 * Note that startAccepting() must be called on the AsyncServerSocket to
335 * cause it to actually start accepting sockets once callbacks have been
338 * @param callback The callback to invoke.
339 * @param eventBase The EventBase to use to invoke the callback. This
340 * parameter may be nullptr, in which case the callback will be invoked in
341 * the AsyncServerSocket's primary EventBase.
342 * @param maxAtOnce The maximum number of connections to accept in this
343 * callback on a single iteration of the event base loop.
344 * This only takes effect when eventBase is non-nullptr.
345 * When using a nullptr eventBase for the callback, the
346 * setMaxAcceptAtOnce() method controls how many
347 * connections the main event base will accept at once.
349 virtual void addAcceptCallback(
350 AcceptCallback *callback,
351 EventBase *eventBase,
352 uint32_t maxAtOnce = kDefaultCallbackAcceptAtOnce);
355 * Remove an AcceptCallback.
357 * This allows a single AcceptCallback to be removed from the round-robin
360 * This method must be invoked from the AsyncServerSocket's primary
361 * EventBase thread. Use EventBase::runInEventBaseThread() to schedule the
362 * operation in the correct EventBase if your code is not in the server
363 * socket's primary EventBase.
365 * Given that the accept callback is being driven by a different EventBase,
366 * the AcceptCallback may continue to be invoked for a short period of time
367 * after removeAcceptCallback() returns in this thread. Once the other
368 * EventBase thread receives the notification to stop, it will call
369 * acceptStopped() on the callback to inform it that it is fully stopped and
370 * will not receive any new sockets.
372 * If the last accept callback is removed while the socket is accepting,
373 * the socket will implicitly pause accepting. If a callback is later added,
374 * it will resume accepting immediately, without requiring startAccepting()
377 * @param callback The callback to uninstall.
378 * @param eventBase The EventBase associated with this callback. This must
379 * be the same EventBase that was used when the callback was installed
380 * with addAcceptCallback().
382 void removeAcceptCallback(AcceptCallback *callback, EventBase *eventBase);
385 * Begin accepting connctions on this socket.
387 * bind() and listen() must be called before calling startAccepting().
389 * When a AsyncServerSocket is initially created, it will not begin
390 * accepting connections until at least one callback has been added and
391 * startAccepting() has been called. startAccepting() can also be used to
392 * resume accepting connections after a call to pauseAccepting().
394 * If startAccepting() is called when there are no accept callbacks
395 * installed, the socket will not actually begin accepting until an accept
398 * This method may only be called from the primary EventBase thread.
400 virtual void startAccepting();
403 * Pause accepting connections.
405 * startAccepting() may be called to resume accepting.
407 * This method may only be called from the primary EventBase thread.
408 * If there are AcceptCallbacks being driven by other EventBase threads they
409 * may continue to receive callbacks for a short period of time after
410 * pauseAccepting() returns.
412 * Unlike removeAcceptCallback() or destroy(), acceptStopped() will not be
413 * called on the AcceptCallback objects simply due to a temporary pause. If
414 * the server socket is later destroyed while paused, acceptStopped() will be
415 * called all of the installed AcceptCallbacks.
417 void pauseAccepting();
420 * Shutdown the listen socket and notify all callbacks that accept has
421 * stopped, but don't close the socket. This invokes shutdown(2) with the
422 * supplied argument. Passing -1 will close the socket now. Otherwise, the
423 * close will be delayed until this object is destroyed.
425 * Only use this if you have reason to pass special flags to shutdown.
426 * Otherwise just destroy the socket.
428 * This method has no effect when a ShutdownSocketSet option is used.
430 * Returns the result of shutdown on sockets_[n-1]
432 int stopAccepting(int shutdownFlags = -1);
435 * Get the maximum number of connections that will be accepted each time
436 * around the event loop.
438 uint32_t getMaxAcceptAtOnce() const {
439 return maxAcceptAtOnce_;
443 * Set the maximum number of connections that will be accepted each time
444 * around the event loop.
446 * This provides a very coarse-grained way of controlling how fast the
447 * AsyncServerSocket will accept connections. If you find that when your
448 * server is overloaded AsyncServerSocket accepts connections more quickly
449 * than your code can process them, you can try lowering this number so that
450 * fewer connections will be accepted each event loop iteration.
452 * For more explicit control over the accept rate, you can also use
453 * pauseAccepting() to temporarily pause accepting when your server is
454 * overloaded, and then use startAccepting() later to resume accepting.
456 void setMaxAcceptAtOnce(uint32_t numConns) {
457 maxAcceptAtOnce_ = numConns;
461 * Get the maximum number of unprocessed messages which a NotificationQueue
464 uint32_t getMaxNumMessagesInQueue() const {
465 return maxNumMsgsInQueue_;
469 * Set the maximum number of unprocessed messages in NotificationQueue.
470 * No new message will be sent to that NotificationQueue if there are more
471 * than such number of unprocessed messages in that queue.
473 * Only works if called before addAcceptCallback.
475 void setMaxNumMessagesInQueue(uint32_t num) {
476 maxNumMsgsInQueue_ = num;
480 * Get the speed of adjusting connection accept rate.
482 double getAcceptRateAdjustSpeed() const {
483 return acceptRateAdjustSpeed_;
487 * Set the speed of adjusting connection accept rate.
489 void setAcceptRateAdjustSpeed(double speed) {
490 acceptRateAdjustSpeed_ = speed;
494 * Get the number of connections dropped by the AsyncServerSocket
496 uint64_t getNumDroppedConnections() const {
497 return numDroppedConnections_;
501 * Set whether or not SO_KEEPALIVE should be enabled on the server socket
502 * (and thus on all subsequently-accepted connections). By default, keepalive
505 * Note that TCP keepalive usually only kicks in after the connection has
506 * been idle for several hours. Applications should almost always have their
507 * own, shorter idle timeout.
509 void setKeepAliveEnabled(bool enabled) {
510 keepAliveEnabled_ = enabled;
512 for (auto& handler : sockets_) {
513 if (handler.socket_ < 0) {
517 int val = (enabled) ? 1 : 0;
518 if (setsockopt(handler.socket_, SOL_SOCKET,
519 SO_KEEPALIVE, &val, sizeof(val)) != 0) {
520 LOG(ERROR) << "failed to set SO_KEEPALIVE on async server socket: %s" <<
527 * Get whether or not SO_KEEPALIVE is enabled on the server socket.
529 bool getKeepAliveEnabled() const {
530 return keepAliveEnabled_;
534 * Set whether or not SO_REUSEPORT should be enabled on the server socket,
535 * allowing multiple binds to the same port
537 void setReusePortEnabled(bool enabled) {
538 reusePortEnabled_ = enabled;
540 for (auto& handler : sockets_) {
541 if (handler.socket_ < 0) {
545 int val = (enabled) ? 1 : 0;
546 if (setsockopt(handler.socket_, SOL_SOCKET,
547 SO_REUSEPORT, &val, sizeof(val)) != 0) {
549 "failed to set SO_REUSEPORT on async server socket " << errno;
550 folly::throwSystemError(errno,
551 "failed to bind to async server socket");
557 * Get whether or not SO_REUSEPORT is enabled on the server socket.
559 bool getReusePortEnabled_() const {
560 return reusePortEnabled_;
564 * Set whether or not the socket should close during exec() (FD_CLOEXEC). By
565 * default, this is enabled
567 void setCloseOnExec(bool closeOnExec) {
568 closeOnExec_ = closeOnExec;
572 * Get whether or not FD_CLOEXEC is enabled on the server socket.
574 bool getCloseOnExec() const {
580 * Protected destructor.
582 * Invoke destroy() instead to destroy the AsyncServerSocket.
584 virtual ~AsyncServerSocket();
587 enum class MessageType {
592 struct QueueMessage {
596 SocketAddress address;
601 * A class to receive notifications to invoke AcceptCallback objects
602 * in other EventBase threads.
604 * A RemoteAcceptor object is created for each AcceptCallback that
605 * is installed in a separate EventBase thread. The RemoteAcceptor
606 * receives notification of new sockets via a NotificationQueue,
607 * and then invokes the AcceptCallback.
610 : private NotificationQueue<QueueMessage>::Consumer {
612 explicit RemoteAcceptor(AcceptCallback *callback)
613 : callback_(callback) {}
617 void start(EventBase *eventBase, uint32_t maxAtOnce, uint32_t maxInQueue);
618 void stop(EventBase* eventBase, AcceptCallback* callback);
620 virtual void messageAvailable(QueueMessage&& message);
622 NotificationQueue<QueueMessage>* getQueue() {
627 AcceptCallback *callback_;
629 NotificationQueue<QueueMessage> queue_;
633 * A struct to keep track of the callbacks associated with this server
636 struct CallbackInfo {
637 CallbackInfo(AcceptCallback *cb, EventBase *evb)
642 AcceptCallback *callback;
643 EventBase *eventBase;
645 RemoteAcceptor* consumer;
648 class BackoffTimeout;
650 virtual void handlerReady(
651 uint16_t events, int socket, sa_family_t family) noexcept;
653 int createSocket(int family);
654 void setupSocket(int fd);
655 void bindSocket(int fd, const SocketAddress& address, bool isExistingSocket);
656 void dispatchSocket(int socket, SocketAddress&& address);
657 void dispatchError(const char *msg, int errnoValue);
659 void backoffTimeoutExpired();
661 CallbackInfo* nextCallback() {
662 CallbackInfo* info = &callbacks_[callbackIndex_];
665 if (callbackIndex_ >= callbacks_.size()) {
672 struct ServerEventHandler : public EventHandler {
673 ServerEventHandler(EventBase* eventBase, int socket,
674 AsyncServerSocket* parent,
675 sa_family_t addressFamily)
676 : EventHandler(eventBase, socket)
677 , eventBase_(eventBase)
680 , addressFamily_(addressFamily) {}
682 ServerEventHandler(const ServerEventHandler& other)
683 : EventHandler(other.eventBase_, other.socket_)
684 , eventBase_(other.eventBase_)
685 , socket_(other.socket_)
686 , parent_(other.parent_)
687 , addressFamily_(other.addressFamily_) {}
689 ServerEventHandler& operator=(
690 const ServerEventHandler& other) {
691 if (this != &other) {
692 eventBase_ = other.eventBase_;
693 socket_ = other.socket_;
694 parent_ = other.parent_;
695 addressFamily_ = other.addressFamily_;
698 attachEventBase(other.eventBase_);
699 changeHandlerFD(other.socket_);
704 // Inherited from EventHandler
705 virtual void handlerReady(uint16_t events) noexcept {
706 parent_->handlerReady(events, socket_, addressFamily_);
709 EventBase* eventBase_;
711 AsyncServerSocket* parent_;
712 sa_family_t addressFamily_;
715 EventBase *eventBase_;
716 std::vector<ServerEventHandler> sockets_;
717 std::vector<int> pendingCloseSockets_;
719 uint32_t maxAcceptAtOnce_;
720 uint32_t maxNumMsgsInQueue_;
721 double acceptRateAdjustSpeed_; //0 to disable auto adjust
723 std::chrono::time_point<std::chrono::steady_clock> lastAccepTimestamp_;
724 uint64_t numDroppedConnections_;
725 uint32_t callbackIndex_;
726 BackoffTimeout *backoffTimeout_;
727 std::vector<CallbackInfo> callbacks_;
728 bool keepAliveEnabled_;
729 bool reusePortEnabled_{false};
731 ShutdownSocketSet* shutdownSocketSet_;