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.
17 #ifndef __STDC_FORMAT_MACROS
18 #define __STDC_FORMAT_MACROS
21 #include <folly/io/async/EventBase.h>
23 #include <folly/ThreadName.h>
24 #include <folly/io/async/NotificationQueue.h>
26 #include <boost/static_assert.hpp>
34 using folly::EventBase;
36 template <typename Callback>
37 class FunctionLoopCallback : public EventBase::LoopCallback {
39 explicit FunctionLoopCallback(Cob&& function)
40 : function_(std::move(function)) {}
42 explicit FunctionLoopCallback(const Cob& function)
43 : function_(function) {}
45 virtual void runLoopCallback() noexcept {
61 * EventBase::FunctionRunner
64 class EventBase::FunctionRunner
65 : public NotificationQueue<std::pair<void (*)(void*), void*>>::Consumer {
67 void messageAvailable(std::pair<void (*)(void*), void*>&& msg) {
69 // In libevent2, internal events do not break the loop.
70 // Most users would expect loop(), followed by runInEventBaseThread(),
71 // to break the loop and check if it should exit or not.
72 // To have similar bejaviour to libevent1.4, tell the loop to break here.
73 // Note that loop() may still continue to loop, but it will also check the
74 // stop_ flag as well as runInLoop callbacks, etc.
75 event_base_loopbreak(getEventBase()->evb_);
77 if (msg.first == nullptr && msg.second == nullptr) {
78 // terminateLoopSoon() sends a null message just to
79 // wake up the loop. We can ignore these messages.
83 // If function is nullptr, just log and move on
85 LOG(ERROR) << "nullptr callback registered to be run in "
86 << "event base thread";
90 // The function should never throw an exception, because we have no
91 // way of knowing what sort of error handling to perform.
93 // If it does throw, log a message and abort the program.
95 msg.first(msg.second);
96 } catch (const std::exception& ex) {
97 LOG(ERROR) << "runInEventBaseThread() function threw a "
98 << typeid(ex).name() << " exception: " << ex.what();
101 LOG(ERROR) << "runInEventBaseThread() function threw an exception";
108 * EventBase::CobTimeout methods
111 void EventBase::CobTimeout::timeoutExpired() noexcept {
112 // For now, we just swallow any exceptions that the callback threw.
115 } catch (const std::exception& ex) {
116 LOG(ERROR) << "EventBase::runAfterDelay() callback threw "
117 << typeid(ex).name() << " exception: " << ex.what();
119 LOG(ERROR) << "EventBase::runAfterDelay() callback threw non-exception "
123 // The CobTimeout object was allocated on the heap by runAfterDelay(),
124 // so delete it now that the it has fired.
132 EventBase::EventBase()
133 : runOnceCallbacks_(nullptr)
136 , evb_(static_cast<event_base*>(event_init()))
140 , avgLoopTime_(2000000)
141 , maxLatencyLoopTime_(avgLoopTime_)
142 , nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
143 , latestLoopCnt_(nextLoopCnt_)
146 , observerSampleCount_(0) {
147 if (UNLIKELY(evb_ == nullptr)) {
148 LOG(ERROR) << "EventBase(): Failed to init event base.";
149 folly::throwSystemError("error in EventBase::EventBase()");
151 VLOG(5) << "EventBase(): Created.";
152 initNotificationQueue();
153 RequestContext::getStaticContext();
156 // takes ownership of the event_base
157 EventBase::EventBase(event_base* evb)
158 : runOnceCallbacks_(nullptr)
165 , avgLoopTime_(2000000)
166 , maxLatencyLoopTime_(avgLoopTime_)
167 , nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
168 , latestLoopCnt_(nextLoopCnt_)
171 , observerSampleCount_(0) {
172 if (UNLIKELY(evb_ == nullptr)) {
173 LOG(ERROR) << "EventBase(): Pass nullptr as event base.";
174 throw std::invalid_argument("EventBase(): event base cannot be nullptr");
176 initNotificationQueue();
177 RequestContext::getStaticContext();
180 EventBase::~EventBase() {
181 // Call all destruction callbacks, before we start cleaning up our state.
182 while (!onDestructionCallbacks_.empty()) {
183 LoopCallback* callback = &onDestructionCallbacks_.front();
184 onDestructionCallbacks_.pop_front();
185 callback->runLoopCallback();
188 // Delete any unfired callback objects, so that we don't leak memory
189 // (Note that we don't fire them. The caller is responsible for cleaning up
190 // its own data structures if it destroys the EventBase with unfired events
192 while (!pendingCobTimeouts_.empty()) {
193 CobTimeout* timeout = &pendingCobTimeouts_.front();
197 while (!noWaitLoopCallbacks_.empty()) {
198 delete &noWaitLoopCallbacks_.front();
201 (void) runLoopCallbacks(false);
203 // Stop consumer before deleting NotificationQueue
204 fnRunner_->stopConsuming();
205 event_base_free(evb_);
206 VLOG(5) << "EventBase(): Destroyed.";
209 int EventBase::getNotificationQueueSize() const {
210 return queue_->size();
213 void EventBase::setMaxReadAtOnce(uint32_t maxAtOnce) {
214 fnRunner_->setMaxReadAtOnce(maxAtOnce);
217 // Set smoothing coefficient for loop load average; input is # of milliseconds
218 // for exp(-1) decay.
219 void EventBase::setLoadAvgMsec(uint32_t ms) {
220 uint64_t us = 1000 * ms;
222 maxLatencyLoopTime_.setTimeInterval(us);
223 avgLoopTime_.setTimeInterval(us);
225 LOG(ERROR) << "non-positive arg to setLoadAvgMsec()";
229 void EventBase::resetLoadAvg(double value) {
230 avgLoopTime_.reset(value);
231 maxLatencyLoopTime_.reset(value);
234 static std::chrono::milliseconds
235 getTimeDelta(std::chrono::steady_clock::time_point* prev) {
236 auto result = std::chrono::steady_clock::now() - *prev;
237 *prev = std::chrono::steady_clock::now();
239 return std::chrono::duration_cast<std::chrono::milliseconds>(result);
242 void EventBase::waitUntilRunning() {
243 while (!isRunning()) {
248 // enters the event_base loop -- will only exit when forced to
249 bool EventBase::loop() {
253 bool EventBase::loopOnce(int flags) {
254 return loopBody(flags | EVLOOP_ONCE);
257 bool EventBase::loopBody(int flags) {
258 VLOG(5) << "EventBase(): Starting loop.";
260 bool ranLoopCallbacks;
261 bool blocking = !(flags & EVLOOP_NONBLOCK);
262 bool once = (flags & EVLOOP_ONCE);
264 loopThread_.store(pthread_self(), std::memory_order_release);
266 if (!name_.empty()) {
267 setThreadName(name_);
270 auto prev = std::chrono::steady_clock::now();
271 int64_t idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
272 std::chrono::steady_clock::now().time_since_epoch()).count();
274 // TODO: Read stop_ atomically with an acquire barrier.
278 // nobody can add loop callbacks from within this thread if
279 // we don't have to handle anything to start with...
280 if (blocking && loopCallbacks_.empty()) {
281 LoopCallbackList callbacks;
282 callbacks.swap(noWaitLoopCallbacks_);
284 while(!callbacks.empty()) {
285 auto* item = &callbacks.front();
286 callbacks.pop_front();
287 item->runLoopCallback();
290 res = event_base_loop(evb_, EVLOOP_ONCE);
292 res = event_base_loop(evb_, EVLOOP_ONCE | EVLOOP_NONBLOCK);
295 ranLoopCallbacks = runLoopCallbacks();
297 int64_t busy = std::chrono::duration_cast<std::chrono::microseconds>(
298 std::chrono::steady_clock::now().time_since_epoch()).count() - startWork_;
299 int64_t idle = startWork_ - idleStart;
301 avgLoopTime_.addSample(idle, busy);
302 maxLatencyLoopTime_.addSample(idle, busy);
305 if (observerSampleCount_++ == observer_->getSampleRate()) {
306 observerSampleCount_ = 0;
307 observer_->loopSample(busy, idle);
311 VLOG(11) << "EventBase " << this << " did not timeout "
312 " loop time guess: " << busy + idle <<
313 " idle time: " << idle <<
314 " busy time: " << busy <<
315 " avgLoopTime: " << avgLoopTime_.get() <<
316 " maxLatencyLoopTime: " << maxLatencyLoopTime_.get() <<
317 " maxLatency_: " << maxLatency_ <<
318 " nothingHandledYet(): "<< nothingHandledYet();
320 // see if our average loop time has exceeded our limit
321 if ((maxLatency_ > 0) &&
322 (maxLatencyLoopTime_.get() > double(maxLatency_))) {
324 // back off temporarily -- don't keep spamming maxLatencyCob_
325 // if we're only a bit over the limit
326 maxLatencyLoopTime_.dampen(0.9);
329 // Our loop run did real work; reset the idle timer
330 idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
331 std::chrono::steady_clock::now().time_since_epoch()).count();
333 // If the event loop indicate that there were no more events, and
334 // we also didn't have any loop callbacks to run, there is nothing left to
336 if (res != 0 && !ranLoopCallbacks) {
337 // Since Notification Queue is marked 'internal' some events may not have
338 // run. Run them manually if so, and continue looping.
340 if (getNotificationQueueSize() > 0) {
341 fnRunner_->handlerReady(0);
347 VLOG(5) << "EventBase " << this << " loop time: " <<
348 getTimeDelta(&prev).count();
354 // Reset stop_ so loop() can be called again
358 LOG(ERROR) << "EventBase: -- error in event loop, res = " << res;
360 } else if (res == 1) {
361 VLOG(5) << "EventBase: ran out of events (exiting loop)!";
362 } else if (res > 1) {
363 LOG(ERROR) << "EventBase: unknown event loop result = " << res;
367 loopThread_.store(0, std::memory_order_release);
369 VLOG(5) << "EventBase(): Done with loop.";
373 void EventBase::loopForever() {
374 // Update the notification queue event to treat it as a normal (non-internal)
375 // event. The notification queue event always remains installed, and the main
376 // loop won't exit with it installed.
377 fnRunner_->stopConsuming();
378 fnRunner_->startConsuming(this, queue_.get());
382 // Restore the notification queue internal flag
383 fnRunner_->stopConsuming();
384 fnRunner_->startConsumingInternal(this, queue_.get());
387 folly::throwSystemError("error in EventBase::loopForever()");
391 bool EventBase::bumpHandlingTime() {
392 VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
393 " (loop) latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
394 if(nothingHandledYet()) {
395 latestLoopCnt_ = nextLoopCnt_;
397 startWork_ = std::chrono::duration_cast<std::chrono::microseconds>(
398 std::chrono::steady_clock::now().time_since_epoch()).count();
400 VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
401 " (loop) startWork_ " << startWork_;
407 void EventBase::terminateLoopSoon() {
408 VLOG(5) << "EventBase(): Received terminateLoopSoon() command.";
410 // Set stop to true, so the event loop will know to exit.
411 // TODO: We should really use an atomic operation here with a release
415 // Call event_base_loopbreak() so that libevent will exit the next time
417 event_base_loopbreak(evb_);
419 // If terminateLoopSoon() is called from another thread,
420 // the EventBase thread might be stuck waiting for events.
421 // In this case, it won't wake up and notice that stop_ is set until it
422 // receives another event. Send an empty frame to the notification queue
423 // so that the event loop will wake up even if there are no other events.
425 // We don't care about the return value of trySendFrame(). If it fails
426 // this likely means the EventBase already has lots of events waiting
429 queue_->putMessage(std::make_pair(nullptr, nullptr));
431 // We don't care if putMessage() fails. This likely means
432 // the EventBase already has lots of events waiting anyway.
436 void EventBase::runInLoop(LoopCallback* callback, bool thisIteration) {
437 DCHECK(isInEventBaseThread());
438 callback->cancelLoopCallback();
439 callback->context_ = RequestContext::saveContext();
440 if (runOnceCallbacks_ != nullptr && thisIteration) {
441 runOnceCallbacks_->push_back(*callback);
443 loopCallbacks_.push_back(*callback);
447 void EventBase::runInLoop(const Cob& cob, bool thisIteration) {
448 DCHECK(isInEventBaseThread());
449 auto wrapper = new FunctionLoopCallback<Cob>(cob);
450 wrapper->context_ = RequestContext::saveContext();
451 if (runOnceCallbacks_ != nullptr && thisIteration) {
452 runOnceCallbacks_->push_back(*wrapper);
454 loopCallbacks_.push_back(*wrapper);
458 void EventBase::runInLoop(Cob&& cob, bool thisIteration) {
459 DCHECK(isInEventBaseThread());
460 auto wrapper = new FunctionLoopCallback<Cob>(std::move(cob));
461 wrapper->context_ = RequestContext::saveContext();
462 if (runOnceCallbacks_ != nullptr && thisIteration) {
463 runOnceCallbacks_->push_back(*wrapper);
465 loopCallbacks_.push_back(*wrapper);
469 void EventBase::runOnDestruction(LoopCallback* callback) {
470 DCHECK(isInEventBaseThread());
471 callback->cancelLoopCallback();
472 onDestructionCallbacks_.push_back(*callback);
475 void EventBase::runBeforeLoop(LoopCallback* callback) {
476 DCHECK(isInEventBaseThread());
477 callback->cancelLoopCallback();
478 noWaitLoopCallbacks_.push_back(*callback);
481 bool EventBase::runInEventBaseThread(void (*fn)(void*), void* arg) {
483 // It will be received by the FunctionRunner in the EventBase's thread.
485 // We try not to schedule nullptr callbacks
487 LOG(ERROR) << "EventBase " << this
488 << ": Scheduling nullptr callbacks is not allowed";
492 // Short-circuit if we are already in our event base
493 if (inRunningEventBaseThread()) {
494 runInLoop(new RunInLoopCallback(fn, arg));
500 queue_->putMessage(std::make_pair(fn, arg));
501 } catch (const std::exception& ex) {
502 LOG(ERROR) << "EventBase " << this << ": failed to schedule function "
503 << fn << "for EventBase thread: " << ex.what();
510 bool EventBase::runInEventBaseThread(const Cob& fn) {
511 // Short-circuit if we are already in our event base
512 if (inRunningEventBaseThread()) {
518 // Allocate a copy of the function so we can pass it to the other thread
519 // The other thread will delete this copy once the function has been run
521 fnCopy = new Cob(fn);
522 } catch (const std::bad_alloc& ex) {
523 LOG(ERROR) << "failed to allocate tr::function copy "
524 << "for runInEventBaseThread()";
528 if (!runInEventBaseThread(&EventBase::runFunctionPtr, fnCopy)) {
536 bool EventBase::runAfterDelay(const Cob& cob,
538 TimeoutManager::InternalEnum in) {
539 CobTimeout* timeout = new CobTimeout(this, cob, in);
540 if (!timeout->scheduleTimeout(milliseconds)) {
545 pendingCobTimeouts_.push_back(*timeout);
549 bool EventBase::runLoopCallbacks(bool setContext) {
550 if (!loopCallbacks_.empty()) {
552 // Swap the loopCallbacks_ list with a temporary list on our stack.
553 // This way we will only run callbacks scheduled at the time
554 // runLoopCallbacks() was invoked.
556 // If any of these callbacks in turn call runInLoop() to schedule more
557 // callbacks, those new callbacks won't be run until the next iteration
558 // around the event loop. This prevents runInLoop() callbacks from being
559 // able to start file descriptor and timeout based events.
560 LoopCallbackList currentCallbacks;
561 currentCallbacks.swap(loopCallbacks_);
562 runOnceCallbacks_ = ¤tCallbacks;
564 while (!currentCallbacks.empty()) {
565 LoopCallback* callback = ¤tCallbacks.front();
566 currentCallbacks.pop_front();
568 RequestContext::setContext(callback->context_);
570 callback->runLoopCallback();
573 runOnceCallbacks_ = nullptr;
579 void EventBase::initNotificationQueue() {
580 // Infinite size queue
581 queue_.reset(new NotificationQueue<std::pair<void (*)(void*), void*>>());
583 // We allocate fnRunner_ separately, rather than declaring it directly
584 // as a member of EventBase solely so that we don't need to include
585 // NotificationQueue.h from EventBase.h
586 fnRunner_.reset(new FunctionRunner());
588 // Mark this as an internal event, so event_base_loop() will return if
589 // there are no other events besides this one installed.
591 // Most callers don't care about the internal notification queue used by
592 // EventBase. The queue is always installed, so if we did count the queue as
593 // an active event, loop() would never exit with no more events to process.
594 // Users can use loopForever() if they do care about the notification queue.
595 // (This is useful for EventBase threads that do nothing but process
596 // runInEventBaseThread() notifications.)
597 fnRunner_->startConsumingInternal(this, queue_.get());
600 void EventBase::SmoothLoopTime::setTimeInterval(uint64_t timeInterval) {
601 expCoeff_ = -1.0/timeInterval;
602 VLOG(11) << "expCoeff_ " << expCoeff_ << " " << __PRETTY_FUNCTION__;
605 void EventBase::SmoothLoopTime::reset(double value) {
609 void EventBase::SmoothLoopTime::addSample(int64_t idle, int64_t busy) {
611 * Position at which the busy sample is considered to be taken.
612 * (Allows to quickly skew our average without editing much code)
614 enum BusySamplePosition {
615 RIGHT = 0, // busy sample placed at the end of the iteration
616 CENTER = 1, // busy sample placed at the middle point of the iteration
617 LEFT = 2, // busy sample placed at the beginning of the iteration
620 VLOG(11) << "idle " << idle << " oldBusyLeftover_ " << oldBusyLeftover_ <<
621 " idle + oldBusyLeftover_ " << idle + oldBusyLeftover_ <<
622 " busy " << busy << " " << __PRETTY_FUNCTION__;
623 idle += oldBusyLeftover_ + busy;
624 oldBusyLeftover_ = (busy * BusySamplePosition::CENTER) / 2;
625 idle -= oldBusyLeftover_;
627 double coeff = exp(idle * expCoeff_);
629 value_ += (1.0 - coeff) * busy;
632 bool EventBase::nothingHandledYet() {
633 VLOG(11) << "latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
634 return (nextLoopCnt_ != latestLoopCnt_);
638 void EventBase::runFunctionPtr(Cob* fn) {
639 // The function should never throw an exception, because we have no
640 // way of knowing what sort of error handling to perform.
642 // If it does throw, log a message and abort the program.
645 } catch (const std::exception &ex) {
646 LOG(ERROR) << "runInEventBaseThread() std::function threw a "
647 << typeid(ex).name() << " exception: " << ex.what();
650 LOG(ERROR) << "runInEventBaseThread() std::function threw an exception";
654 // The function object was allocated by runInEventBaseThread().
655 // Delete it once it has been run.
659 EventBase::RunInLoopCallback::RunInLoopCallback(void (*fn)(void*), void* arg)
663 void EventBase::RunInLoopCallback::runLoopCallback() noexcept {
668 void EventBase::attachTimeoutManager(AsyncTimeout* obj,
669 InternalEnum internal) {
671 struct event* ev = obj->getEvent();
672 assert(ev->ev_base == nullptr);
674 event_base_set(getLibeventBase(), ev);
675 if (internal == AsyncTimeout::InternalEnum::INTERNAL) {
676 // Set the EVLIST_INTERNAL flag
677 ev->ev_flags |= EVLIST_INTERNAL;
681 void EventBase::detachTimeoutManager(AsyncTimeout* obj) {
683 struct event* ev = obj->getEvent();
684 ev->ev_base = nullptr;
687 bool EventBase::scheduleTimeout(AsyncTimeout* obj,
688 std::chrono::milliseconds timeout) {
689 assert(isInEventBaseThread());
690 // Set up the timeval and add the event
692 tv.tv_sec = timeout.count() / 1000LL;
693 tv.tv_usec = (timeout.count() % 1000LL) * 1000LL;
695 struct event* ev = obj->getEvent();
696 if (event_add(ev, &tv) < 0) {
697 LOG(ERROR) << "EventBase: failed to schedule timeout: " << strerror(errno);
704 void EventBase::cancelTimeout(AsyncTimeout* obj) {
705 assert(isInEventBaseThread());
706 struct event* ev = obj->getEvent();
707 if (EventUtil::isEventRegistered(ev)) {
712 void EventBase::setName(const std::string& name) {
713 assert(isInEventBaseThread());
717 setThreadName(loopThread_.load(std::memory_order_relaxed),
722 const std::string& EventBase::getName() {
723 assert(isInEventBaseThread());
727 const char* EventBase::getLibeventVersion() { return event_get_version(); }
728 const char* EventBase::getLibeventMethod() { return event_get_method(); }