2 * Copyright 2014 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;
63 class AcceptCallback {
65 virtual ~AcceptCallback() {}
68 * connectionAccepted() is called whenever a new client connection is
71 * The AcceptCallback will remain installed after connectionAccepted()
74 * @param fd The newly accepted client socket. The AcceptCallback
75 * assumes ownership of this socket, and is responsible
76 * for closing it when done. The newly accepted file
77 * descriptor will have already been put into
79 * @param clientAddr A reference to a TSocketAddress struct containing the
80 * client's address. This struct is only guaranteed to
81 * remain valid until connectionAccepted() returns.
83 virtual void connectionAccepted(int fd,
84 const SocketAddress& clientAddr)
88 * acceptError() is called if an error occurs while accepting.
90 * The AcceptCallback will remain installed even after an accept error,
91 * as the errors are typically somewhat transient, such as being out of
92 * file descriptors. The server socket must be explicitly stopped if you
93 * wish to stop accepting after an error.
95 * @param ex An exception representing the error.
97 virtual void acceptError(const std::exception& ex) noexcept = 0;
100 * acceptStarted() will be called in the callback's EventBase thread
101 * after this callback has been added to the AsyncServerSocket.
103 * acceptStarted() will be called before any calls to connectionAccepted()
104 * or acceptError() are made on this callback.
106 * acceptStarted() makes it easier for callbacks to perform initialization
107 * inside the callback thread. (The call to addAcceptCallback() must
108 * always be made from the AsyncServerSocket's primary EventBase thread.
109 * acceptStarted() provides a hook that will always be invoked in the
110 * callback's thread.)
112 * Note that the call to acceptStarted() is made once the callback is
113 * added, regardless of whether or not the AsyncServerSocket is actually
114 * accepting at the moment. acceptStarted() will be called even if the
115 * AsyncServerSocket is paused when the callback is added (including if
116 * the initial call to startAccepting() on the AsyncServerSocket has not
119 virtual void acceptStarted() noexcept {}
122 * acceptStopped() will be called when this AcceptCallback is removed from
123 * the AsyncServerSocket, or when the AsyncServerSocket is destroyed,
124 * whichever occurs first.
126 * No more calls to connectionAccepted() or acceptError() will be made
127 * after acceptStopped() is invoked.
129 virtual void acceptStopped() noexcept {}
132 static const uint32_t kDefaultMaxAcceptAtOnce = 30;
133 static const uint32_t kDefaultCallbackAcceptAtOnce = 5;
134 static const uint32_t kDefaultMaxMessagesInQueue = 0;
136 * Create a new AsyncServerSocket with the specified EventBase.
138 * @param eventBase The EventBase to use for driving the asynchronous I/O.
139 * If this parameter is nullptr, attachEventBase() must be
140 * called before this socket can begin accepting
143 explicit AsyncServerSocket(EventBase* eventBase = nullptr);
146 * Helper function to create a shared_ptr<AsyncServerSocket>.
148 * This passes in the correct destructor object, since AsyncServerSocket's
149 * destructor is protected and cannot be invoked directly.
151 static std::shared_ptr<AsyncServerSocket>
152 newSocket(EventBase* evb = nullptr) {
153 return std::shared_ptr<AsyncServerSocket>(new AsyncServerSocket(evb),
157 void setShutdownSocketSet(ShutdownSocketSet* newSS);
160 * Destroy the socket.
162 * AsyncServerSocket::destroy() must be called to destroy the socket.
163 * The normal destructor is private, and should not be invoked directly.
164 * This prevents callers from deleting a AsyncServerSocket while it is
165 * invoking a callback.
167 * destroy() must be invoked from the socket's primary EventBase thread.
169 * If there are AcceptCallbacks still installed when destroy() is called,
170 * acceptStopped() will be called on these callbacks to notify them that
171 * accepting has stopped. Accept callbacks being driven by other EventBase
172 * threads may continue to receive new accept callbacks for a brief period of
173 * time after destroy() returns. They will not receive any more callback
174 * invocations once acceptStopped() is invoked.
176 virtual void destroy();
179 * Attach this AsyncServerSocket to its primary EventBase.
181 * This may only be called if the AsyncServerSocket is not already attached
182 * to a EventBase. The AsyncServerSocket must be attached to a EventBase
183 * before it can begin accepting connections.
185 void attachEventBase(EventBase *eventBase);
188 * Detach the AsyncServerSocket from its primary EventBase.
190 * detachEventBase() may only be called if the AsyncServerSocket is not
191 * currently accepting connections.
193 void detachEventBase();
196 * Get the EventBase used by this socket.
198 EventBase* getEventBase() const {
203 * Create a AsyncServerSocket from an existing socket file descriptor.
205 * useExistingSocket() will cause the AsyncServerSocket to take ownership of
206 * the specified file descriptor, and use it to listen for new connections.
207 * The AsyncServerSocket will close the file descriptor when it is
210 * useExistingSocket() must be called before bind() or listen().
212 * The supplied file descriptor will automatically be put into non-blocking
213 * mode. The caller may have already directly called bind() and possibly
214 * listen on the file descriptor. If so the caller should skip calling the
215 * corresponding AsyncServerSocket::bind() and listen() methods.
217 * On error a TTransportException will be thrown and the caller will retain
218 * ownership of the file descriptor.
220 void useExistingSocket(int fd);
221 void useExistingSockets(const std::vector<int>& fds);
224 * Return the underlying file descriptor
226 std::vector<int> getSockets() const {
227 std::vector<int> sockets;
228 for (auto& handler : sockets_) {
229 sockets.push_back(handler.socket_);
235 * Backwards compatible getSocket, warns if > 1 socket
237 int getSocket() const {
238 if (sockets_.size() > 1) {
239 VLOG(2) << "Warning: getSocket can return multiple fds, " <<
240 "but getSockets was not called, so only returning the first";
242 if (sockets_.size() == 0) {
245 return sockets_[0].socket_;
250 * Bind to the specified address.
252 * This must be called from the primary EventBase thread.
254 * Throws TTransportException on error.
256 virtual void bind(const SocketAddress& address);
259 * Bind to the specified port for the specified addresses.
261 * This must be called from the primary EventBase thread.
263 * Throws TTransportException on error.
266 const std::vector<IPAddress>& ipAddresses,
270 * Bind to the specified port.
272 * This must be called from the primary EventBase thread.
274 * Throws TTransportException on error.
276 virtual void bind(uint16_t port);
279 * Get the local address to which the socket is bound.
281 * Throws TTransportException on error.
283 void getAddress(SocketAddress* addressReturn) const;
286 * Get all the local addresses to which the socket is bound.
288 * Throws TTransportException on error.
290 std::vector<SocketAddress> getAddresses() const;
293 * Begin listening for connections.
295 * This calls ::listen() with the specified backlog.
297 * Once listen() is invoked the socket will actually be open so that remote
298 * clients may establish connections. (Clients that attempt to connect
299 * before listen() is called will receive a connection refused error.)
301 * At least one callback must be set and startAccepting() must be called to
302 * actually begin notifying the accept callbacks of newly accepted
303 * connections. The backlog parameter controls how many connections the
304 * kernel will accept and buffer internally while the accept callbacks are
305 * paused (or if accepting is enabled but the callbacks cannot keep up).
307 * bind() must be called before calling listen().
308 * listen() must be called from the primary EventBase thread.
310 * Throws TTransportException on error.
312 virtual void listen(int backlog);
315 * Add an AcceptCallback.
317 * When a new socket is accepted, one of the AcceptCallbacks will be invoked
318 * with the new socket. The AcceptCallbacks are invoked in a round-robin
319 * fashion. This allows the accepted sockets to distributed among a pool of
320 * threads, each running its own EventBase object. This is a common model,
321 * since most asynchronous-style servers typically run one EventBase thread
324 * The EventBase object associated with each AcceptCallback must be running
325 * its loop. If the EventBase loop is not running, sockets will still be
326 * scheduled for the callback, but the callback cannot actually get invoked
327 * until the loop runs.
329 * This method must be invoked from the AsyncServerSocket's primary
332 * Note that startAccepting() must be called on the AsyncServerSocket to
333 * cause it to actually start accepting sockets once callbacks have been
336 * @param callback The callback to invoke.
337 * @param eventBase The EventBase to use to invoke the callback. This
338 * parameter may be nullptr, in which case the callback will be invoked in
339 * the AsyncServerSocket's primary EventBase.
340 * @param maxAtOnce The maximum number of connections to accept in this
341 * callback on a single iteration of the event base loop.
342 * This only takes effect when eventBase is non-nullptr.
343 * When using a nullptr eventBase for the callback, the
344 * setMaxAcceptAtOnce() method controls how many
345 * connections the main event base will accept at once.
347 virtual void addAcceptCallback(
348 AcceptCallback *callback,
349 EventBase *eventBase,
350 uint32_t maxAtOnce = kDefaultCallbackAcceptAtOnce);
353 * Remove an AcceptCallback.
355 * This allows a single AcceptCallback to be removed from the round-robin
358 * This method must be invoked from the AsyncServerSocket's primary
359 * EventBase thread. Use EventBase::runInEventBaseThread() to schedule the
360 * operation in the correct EventBase if your code is not in the server
361 * socket's primary EventBase.
363 * Given that the accept callback is being driven by a different EventBase,
364 * the AcceptCallback may continue to be invoked for a short period of time
365 * after removeAcceptCallback() returns in this thread. Once the other
366 * EventBase thread receives the notification to stop, it will call
367 * acceptStopped() on the callback to inform it that it is fully stopped and
368 * will not receive any new sockets.
370 * If the last accept callback is removed while the socket is accepting,
371 * the socket will implicitly pause accepting. If a callback is later added,
372 * it will resume accepting immediately, without requiring startAccepting()
375 * @param callback The callback to uninstall.
376 * @param eventBase The EventBase associated with this callback. This must
377 * be the same EventBase that was used when the callback was installed
378 * with addAcceptCallback().
380 void removeAcceptCallback(AcceptCallback *callback, EventBase *eventBase);
383 * Begin accepting connctions on this socket.
385 * bind() and listen() must be called before calling startAccepting().
387 * When a AsyncServerSocket is initially created, it will not begin
388 * accepting connections until at least one callback has been added and
389 * startAccepting() has been called. startAccepting() can also be used to
390 * resume accepting connections after a call to pauseAccepting().
392 * If startAccepting() is called when there are no accept callbacks
393 * installed, the socket will not actually begin accepting until an accept
396 * This method may only be called from the primary EventBase thread.
398 virtual void startAccepting();
401 * Pause accepting connections.
403 * startAccepting() may be called to resume accepting.
405 * This method may only be called from the primary EventBase thread.
406 * If there are AcceptCallbacks being driven by other EventBase threads they
407 * may continue to receive callbacks for a short period of time after
408 * pauseAccepting() returns.
410 * Unlike removeAcceptCallback() or destroy(), acceptStopped() will not be
411 * called on the AcceptCallback objects simply due to a temporary pause. If
412 * the server socket is later destroyed while paused, acceptStopped() will be
413 * called all of the installed AcceptCallbacks.
415 void pauseAccepting();
418 * Shutdown the listen socket and notify all callbacks that accept has
419 * stopped, but don't close the socket. This invokes shutdown(2) with the
420 * supplied argument. Passing -1 will close the socket now. Otherwise, the
421 * close will be delayed until this object is destroyed.
423 * Only use this if you have reason to pass special flags to shutdown.
424 * Otherwise just destroy the socket.
426 * This method has no effect when a ShutdownSocketSet option is used.
428 * Returns the result of shutdown on sockets_[n-1]
430 int stopAccepting(int shutdownFlags = -1);
433 * Get the maximum number of connections that will be accepted each time
434 * around the event loop.
436 uint32_t getMaxAcceptAtOnce() const {
437 return maxAcceptAtOnce_;
441 * Set the maximum number of connections that will be accepted each time
442 * around the event loop.
444 * This provides a very coarse-grained way of controlling how fast the
445 * AsyncServerSocket will accept connections. If you find that when your
446 * server is overloaded AsyncServerSocket accepts connections more quickly
447 * than your code can process them, you can try lowering this number so that
448 * fewer connections will be accepted each event loop iteration.
450 * For more explicit control over the accept rate, you can also use
451 * pauseAccepting() to temporarily pause accepting when your server is
452 * overloaded, and then use startAccepting() later to resume accepting.
454 void setMaxAcceptAtOnce(uint32_t numConns) {
455 maxAcceptAtOnce_ = numConns;
459 * Get the maximum number of unprocessed messages which a NotificationQueue
462 uint32_t getMaxNumMessagesInQueue() const {
463 return maxNumMsgsInQueue_;
467 * Set the maximum number of unprocessed messages in NotificationQueue.
468 * No new message will be sent to that NotificationQueue if there are more
469 * than such number of unprocessed messages in that queue.
471 * Only works if called before addAcceptCallback.
473 void setMaxNumMessagesInQueue(uint32_t num) {
474 maxNumMsgsInQueue_ = num;
478 * Get the speed of adjusting connection accept rate.
480 double getAcceptRateAdjustSpeed() const {
481 return acceptRateAdjustSpeed_;
485 * Set the speed of adjusting connection accept rate.
487 void setAcceptRateAdjustSpeed(double speed) {
488 acceptRateAdjustSpeed_ = speed;
492 * Get the number of connections dropped by the AsyncServerSocket
494 uint64_t getNumDroppedConnections() const {
495 return numDroppedConnections_;
499 * Set whether or not SO_KEEPALIVE should be enabled on the server socket
500 * (and thus on all subsequently-accepted connections). By default, keepalive
503 * Note that TCP keepalive usually only kicks in after the connection has
504 * been idle for several hours. Applications should almost always have their
505 * own, shorter idle timeout.
507 void setKeepAliveEnabled(bool enabled) {
508 keepAliveEnabled_ = enabled;
510 for (auto& handler : sockets_) {
511 if (handler.socket_ < 0) {
515 int val = (enabled) ? 1 : 0;
516 if (setsockopt(handler.socket_, SOL_SOCKET,
517 SO_KEEPALIVE, &val, sizeof(val)) != 0) {
518 LOG(ERROR) << "failed to set SO_KEEPALIVE on async server socket: %s" <<
525 * Get whether or not SO_KEEPALIVE is enabled on the server socket.
527 bool getKeepAliveEnabled() const {
528 return keepAliveEnabled_;
532 * Set whether or not SO_REUSEPORT should be enabled on the server socket,
533 * allowing multiple binds to the same port
535 void setReusePortEnabled(bool enabled) {
536 reusePortEnabled_ = enabled;
538 for (auto& handler : sockets_) {
539 if (handler.socket_ < 0) {
543 int val = (enabled) ? 1 : 0;
544 if (setsockopt(handler.socket_, SOL_SOCKET,
545 SO_REUSEPORT, &val, sizeof(val)) != 0) {
547 "failed to set SO_REUSEPORT on async server socket " << errno;
548 folly::throwSystemError(errno,
549 "failed to bind to async server socket");
555 * Get whether or not SO_REUSEPORT is enabled on the server socket.
557 bool getReusePortEnabled_() const {
558 return reusePortEnabled_;
562 * Set whether or not the socket should close during exec() (FD_CLOEXEC). By
563 * default, this is enabled
565 void setCloseOnExec(bool closeOnExec) {
566 closeOnExec_ = closeOnExec;
570 * Get whether or not FD_CLOEXEC is enabled on the server socket.
572 bool getCloseOnExec() const {
578 * Protected destructor.
580 * Invoke destroy() instead to destroy the AsyncServerSocket.
582 virtual ~AsyncServerSocket();
585 enum class MessageType {
590 struct QueueMessage {
594 SocketAddress address;
599 * A class to receive notifications to invoke AcceptCallback objects
600 * in other EventBase threads.
602 * A RemoteAcceptor object is created for each AcceptCallback that
603 * is installed in a separate EventBase thread. The RemoteAcceptor
604 * receives notification of new sockets via a NotificationQueue,
605 * and then invokes the AcceptCallback.
608 : private NotificationQueue<QueueMessage>::Consumer {
610 explicit RemoteAcceptor(AcceptCallback *callback)
611 : callback_(callback) {}
615 void start(EventBase *eventBase, uint32_t maxAtOnce, uint32_t maxInQueue);
616 void stop(EventBase* eventBase, AcceptCallback* callback);
618 virtual void messageAvailable(QueueMessage&& message);
620 NotificationQueue<QueueMessage>* getQueue() {
625 AcceptCallback *callback_;
627 NotificationQueue<QueueMessage> queue_;
631 * A struct to keep track of the callbacks associated with this server
634 struct CallbackInfo {
635 CallbackInfo(AcceptCallback *cb, EventBase *evb)
640 AcceptCallback *callback;
641 EventBase *eventBase;
643 RemoteAcceptor* consumer;
646 class BackoffTimeout;
648 virtual void handlerReady(
649 uint16_t events, int socket, sa_family_t family) noexcept;
651 int createSocket(int family);
652 void setupSocket(int fd);
653 void bindSocket(int fd, const SocketAddress& address, bool isExistingSocket);
654 void dispatchSocket(int socket, SocketAddress&& address);
655 void dispatchError(const char *msg, int errnoValue);
657 void backoffTimeoutExpired();
659 CallbackInfo* nextCallback() {
660 CallbackInfo* info = &callbacks_[callbackIndex_];
663 if (callbackIndex_ >= callbacks_.size()) {
670 struct ServerEventHandler : public EventHandler {
671 ServerEventHandler(EventBase* eventBase, int socket,
672 AsyncServerSocket* parent,
673 sa_family_t addressFamily)
674 : EventHandler(eventBase, socket)
675 , eventBase_(eventBase)
678 , addressFamily_(addressFamily) {}
680 ServerEventHandler(const ServerEventHandler& other)
681 : EventHandler(other.eventBase_, other.socket_)
682 , eventBase_(other.eventBase_)
683 , socket_(other.socket_)
684 , parent_(other.parent_)
685 , addressFamily_(other.addressFamily_) {}
687 ServerEventHandler& operator=(
688 const ServerEventHandler& other) {
689 if (this != &other) {
690 eventBase_ = other.eventBase_;
691 socket_ = other.socket_;
692 parent_ = other.parent_;
693 addressFamily_ = other.addressFamily_;
696 attachEventBase(other.eventBase_);
697 changeHandlerFD(other.socket_);
702 // Inherited from EventHandler
703 virtual void handlerReady(uint16_t events) noexcept {
704 parent_->handlerReady(events, socket_, addressFamily_);
707 EventBase* eventBase_;
709 AsyncServerSocket* parent_;
710 sa_family_t addressFamily_;
713 EventBase *eventBase_;
714 std::vector<ServerEventHandler> sockets_;
715 std::vector<int> pendingCloseSockets_;
717 uint32_t maxAcceptAtOnce_;
718 uint32_t maxNumMsgsInQueue_;
719 double acceptRateAdjustSpeed_; //0 to disable auto adjust
721 std::chrono::time_point<std::chrono::steady_clock> lastAccepTimestamp_;
722 uint64_t numDroppedConnections_;
723 uint32_t callbackIndex_;
724 BackoffTimeout *backoffTimeout_;
725 std::vector<CallbackInfo> callbacks_;
726 bool keepAliveEnabled_;
727 bool reusePortEnabled_{false};
729 ShutdownSocketSet* shutdownSocketSet_;