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.
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/EventBaseLocal.h>
25 #include <folly/io/async/NotificationQueue.h>
27 #include <boost/static_assert.hpp>
28 #include <condition_variable>
37 using folly::EventBase;
39 template <typename Callback>
40 class FunctionLoopCallback : public EventBase::LoopCallback {
42 explicit FunctionLoopCallback(Cob&& function)
43 : function_(std::move(function)) {}
45 explicit FunctionLoopCallback(const Cob& function)
46 : function_(function) {}
48 void runLoopCallback() noexcept override {
64 * EventBase::FunctionRunner
67 class EventBase::FunctionRunner
68 : public NotificationQueue<std::pair<void (*)(void*), void*>>::Consumer {
70 void messageAvailable(std::pair<void (*)(void*), void*>&& msg) override {
72 // In libevent2, internal events do not break the loop.
73 // Most users would expect loop(), followed by runInEventBaseThread(),
74 // to break the loop and check if it should exit or not.
75 // To have similar bejaviour to libevent1.4, tell the loop to break here.
76 // Note that loop() may still continue to loop, but it will also check the
77 // stop_ flag as well as runInLoop callbacks, etc.
78 event_base_loopbreak(getEventBase()->evb_);
80 if (msg.first == nullptr && msg.second == nullptr) {
81 // terminateLoopSoon() sends a null message just to
82 // wake up the loop. We can ignore these messages.
86 // If function is nullptr, just log and move on
88 LOG(ERROR) << "nullptr callback registered to be run in "
89 << "event base thread";
93 // The function should never throw an exception, because we have no
94 // way of knowing what sort of error handling to perform.
96 // If it does throw, log a message and abort the program.
98 msg.first(msg.second);
99 } catch (const std::exception& ex) {
100 LOG(ERROR) << "runInEventBaseThread() function threw a "
101 << typeid(ex).name() << " exception: " << ex.what();
104 LOG(ERROR) << "runInEventBaseThread() function threw an exception";
111 * EventBase::CobTimeout methods
114 void EventBase::CobTimeout::timeoutExpired() noexcept {
115 // For now, we just swallow any exceptions that the callback threw.
118 } catch (const std::exception& ex) {
119 LOG(ERROR) << "EventBase::runAfterDelay() callback threw "
120 << typeid(ex).name() << " exception: " << ex.what();
122 LOG(ERROR) << "EventBase::runAfterDelay() callback threw non-exception "
126 // The CobTimeout object was allocated on the heap by runAfterDelay(),
127 // so delete it now that the it has fired.
132 // The interface used to libevent is not thread-safe. Calls to
133 // event_init() and event_base_free() directly modify an internal
134 // global 'current_base', so a mutex is required to protect this.
136 // event_init() should only ever be called once. Subsequent calls
137 // should be made to event_base_new(). We can recognise that
138 // event_init() has already been called by simply inspecting current_base.
139 static std::mutex libevent_mutex_;
145 EventBase::EventBase(bool enableTimeMeasurement)
146 : runOnceCallbacks_(nullptr)
152 , avgLoopTime_(2000000)
153 , maxLatencyLoopTime_(avgLoopTime_)
154 , enableTimeMeasurement_(enableTimeMeasurement)
155 , nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
156 , latestLoopCnt_(nextLoopCnt_)
159 , observerSampleCount_(0)
160 , executionObserver_(nullptr) {
162 std::lock_guard<std::mutex> lock(libevent_mutex_);
164 // The value 'current_base' (libevent 1) or
165 // 'event_global_current_base_' (libevent 2) is filled in by event_set(),
166 // allowing examination of its value without an explicit reference here.
167 // If ev.ev_base is NULL, then event_init() must be called, otherwise
168 // call event_base_new().
170 event_set(&ev, 0, 0, nullptr, nullptr);
171 evb_ = (ev.ev_base) ? event_base_new() : event_init();
173 if (UNLIKELY(evb_ == nullptr)) {
174 LOG(ERROR) << "EventBase(): Failed to init event base.";
175 folly::throwSystemError("error in EventBase::EventBase()");
177 VLOG(5) << "EventBase(): Created.";
178 initNotificationQueue();
179 RequestContext::saveContext();
182 // takes ownership of the event_base
183 EventBase::EventBase(event_base* evb, bool enableTimeMeasurement)
184 : runOnceCallbacks_(nullptr)
191 , avgLoopTime_(2000000)
192 , maxLatencyLoopTime_(avgLoopTime_)
193 , enableTimeMeasurement_(enableTimeMeasurement)
194 , nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
195 , latestLoopCnt_(nextLoopCnt_)
198 , observerSampleCount_(0)
199 , executionObserver_(nullptr) {
200 if (UNLIKELY(evb_ == nullptr)) {
201 LOG(ERROR) << "EventBase(): Pass nullptr as event base.";
202 throw std::invalid_argument("EventBase(): event base cannot be nullptr");
204 initNotificationQueue();
205 RequestContext::saveContext();
208 EventBase::~EventBase() {
209 // Call all destruction callbacks, before we start cleaning up our state.
210 while (!onDestructionCallbacks_.empty()) {
211 LoopCallback* callback = &onDestructionCallbacks_.front();
212 onDestructionCallbacks_.pop_front();
213 callback->runLoopCallback();
216 // Delete any unfired callback objects, so that we don't leak memory
217 // (Note that we don't fire them. The caller is responsible for cleaning up
218 // its own data structures if it destroys the EventBase with unfired events
220 while (!pendingCobTimeouts_.empty()) {
221 CobTimeout* timeout = &pendingCobTimeouts_.front();
225 while (!runBeforeLoopCallbacks_.empty()) {
226 delete &runBeforeLoopCallbacks_.front();
229 (void) runLoopCallbacks(false);
231 if (!fnRunner_->consumeUntilDrained()) {
232 LOG(ERROR) << "~EventBase(): Unable to drain notification queue";
235 // Stop consumer before deleting NotificationQueue
236 fnRunner_->stopConsuming();
238 std::lock_guard<std::mutex> lock(libevent_mutex_);
239 event_base_free(evb_);
243 std::lock_guard<std::mutex> lock(localStorageMutex_);
244 for (auto storage : localStorageToDtor_) {
245 storage->onEventBaseDestruction(*this);
248 VLOG(5) << "EventBase(): Destroyed.";
251 int EventBase::getNotificationQueueSize() const {
252 return queue_->size();
255 void EventBase::setMaxReadAtOnce(uint32_t maxAtOnce) {
256 fnRunner_->setMaxReadAtOnce(maxAtOnce);
259 // Set smoothing coefficient for loop load average; input is # of milliseconds
260 // for exp(-1) decay.
261 void EventBase::setLoadAvgMsec(uint32_t ms) {
262 assert(enableTimeMeasurement_);
263 uint64_t us = 1000 * ms;
265 maxLatencyLoopTime_.setTimeInterval(us);
266 avgLoopTime_.setTimeInterval(us);
268 LOG(ERROR) << "non-positive arg to setLoadAvgMsec()";
272 void EventBase::resetLoadAvg(double value) {
273 assert(enableTimeMeasurement_);
274 avgLoopTime_.reset(value);
275 maxLatencyLoopTime_.reset(value);
278 static std::chrono::milliseconds
279 getTimeDelta(std::chrono::steady_clock::time_point* prev) {
280 auto result = std::chrono::steady_clock::now() - *prev;
281 *prev = std::chrono::steady_clock::now();
283 return std::chrono::duration_cast<std::chrono::milliseconds>(result);
286 void EventBase::waitUntilRunning() {
287 while (!isRunning()) {
292 // enters the event_base loop -- will only exit when forced to
293 bool EventBase::loop() {
297 bool EventBase::loopOnce(int flags) {
298 return loopBody(flags | EVLOOP_ONCE);
301 bool EventBase::loopBody(int flags) {
302 VLOG(5) << "EventBase(): Starting loop.";
304 bool ranLoopCallbacks;
305 bool blocking = !(flags & EVLOOP_NONBLOCK);
306 bool once = (flags & EVLOOP_ONCE);
308 // time-measurement variables.
309 std::chrono::steady_clock::time_point prev;
314 loopThread_.store(pthread_self(), std::memory_order_release);
316 if (!name_.empty()) {
317 setThreadName(name_);
320 if (enableTimeMeasurement_) {
321 prev = std::chrono::steady_clock::now();
322 idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
323 std::chrono::steady_clock::now().time_since_epoch()).count();
326 while (!stop_.load(std::memory_order_acquire)) {
329 // Run the before loop callbacks
330 LoopCallbackList callbacks;
331 callbacks.swap(runBeforeLoopCallbacks_);
333 while(!callbacks.empty()) {
334 auto* item = &callbacks.front();
335 callbacks.pop_front();
336 item->runLoopCallback();
339 // nobody can add loop callbacks from within this thread if
340 // we don't have to handle anything to start with...
341 if (blocking && loopCallbacks_.empty()) {
342 res = event_base_loop(evb_, EVLOOP_ONCE);
344 res = event_base_loop(evb_, EVLOOP_ONCE | EVLOOP_NONBLOCK);
347 ranLoopCallbacks = runLoopCallbacks();
349 if (enableTimeMeasurement_) {
350 busy = std::chrono::duration_cast<std::chrono::microseconds>(
351 std::chrono::steady_clock::now().time_since_epoch()).count() -
353 idle = startWork_ - idleStart;
355 avgLoopTime_.addSample(idle, busy);
356 maxLatencyLoopTime_.addSample(idle, busy);
359 if (observerSampleCount_++ == observer_->getSampleRate()) {
360 observerSampleCount_ = 0;
361 observer_->loopSample(busy, idle);
365 VLOG(11) << "EventBase " << this << " did not timeout "
366 " loop time guess: " << busy + idle <<
367 " idle time: " << idle <<
368 " busy time: " << busy <<
369 " avgLoopTime: " << avgLoopTime_.get() <<
370 " maxLatencyLoopTime: " << maxLatencyLoopTime_.get() <<
371 " maxLatency_: " << maxLatency_ <<
372 " nothingHandledYet(): "<< nothingHandledYet();
374 // see if our average loop time has exceeded our limit
375 if ((maxLatency_ > 0) &&
376 (maxLatencyLoopTime_.get() > double(maxLatency_))) {
378 // back off temporarily -- don't keep spamming maxLatencyCob_
379 // if we're only a bit over the limit
380 maxLatencyLoopTime_.dampen(0.9);
383 // Our loop run did real work; reset the idle timer
384 idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
385 std::chrono::steady_clock::now().time_since_epoch()).count();
387 VLOG(11) << "EventBase " << this << " did not timeout "
388 " time measurement is disabled "
389 " nothingHandledYet(): "<< nothingHandledYet();
392 // If the event loop indicate that there were no more events, and
393 // we also didn't have any loop callbacks to run, there is nothing left to
395 if (res != 0 && !ranLoopCallbacks) {
396 // Since Notification Queue is marked 'internal' some events may not have
397 // run. Run them manually if so, and continue looping.
399 if (getNotificationQueueSize() > 0) {
400 fnRunner_->handlerReady(0);
406 if (enableTimeMeasurement_) {
407 VLOG(5) << "EventBase " << this << " loop time: " <<
408 getTimeDelta(&prev).count();
415 // Reset stop_ so loop() can be called again
419 LOG(ERROR) << "EventBase: -- error in event loop, res = " << res;
421 } else if (res == 1) {
422 VLOG(5) << "EventBase: ran out of events (exiting loop)!";
423 } else if (res > 1) {
424 LOG(ERROR) << "EventBase: unknown event loop result = " << res;
428 loopThread_.store(0, std::memory_order_release);
430 VLOG(5) << "EventBase(): Done with loop.";
434 void EventBase::loopForever() {
435 // Update the notification queue event to treat it as a normal (non-internal)
436 // event. The notification queue event always remains installed, and the main
437 // loop won't exit with it installed.
438 fnRunner_->stopConsuming();
439 fnRunner_->startConsuming(this, queue_.get());
443 // Restore the notification queue internal flag
444 fnRunner_->stopConsuming();
445 fnRunner_->startConsumingInternal(this, queue_.get());
448 folly::throwSystemError("error in EventBase::loopForever()");
452 bool EventBase::bumpHandlingTime() {
453 VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
454 " (loop) latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
455 if(nothingHandledYet()) {
456 latestLoopCnt_ = nextLoopCnt_;
458 startWork_ = std::chrono::duration_cast<std::chrono::microseconds>(
459 std::chrono::steady_clock::now().time_since_epoch()).count();
461 VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
462 " (loop) startWork_ " << startWork_;
468 void EventBase::terminateLoopSoon() {
469 VLOG(5) << "EventBase(): Received terminateLoopSoon() command.";
471 // Set stop to true, so the event loop will know to exit.
472 // TODO: We should really use an atomic operation here with a release
476 // Call event_base_loopbreak() so that libevent will exit the next time
478 event_base_loopbreak(evb_);
480 // If terminateLoopSoon() is called from another thread,
481 // the EventBase thread might be stuck waiting for events.
482 // In this case, it won't wake up and notice that stop_ is set until it
483 // receives another event. Send an empty frame to the notification queue
484 // so that the event loop will wake up even if there are no other events.
486 // We don't care about the return value of trySendFrame(). If it fails
487 // this likely means the EventBase already has lots of events waiting
490 queue_->putMessage(std::make_pair(nullptr, nullptr));
492 // We don't care if putMessage() fails. This likely means
493 // the EventBase already has lots of events waiting anyway.
497 void EventBase::runInLoop(LoopCallback* callback, bool thisIteration) {
498 DCHECK(isInEventBaseThread());
499 callback->cancelLoopCallback();
500 callback->context_ = RequestContext::saveContext();
501 if (runOnceCallbacks_ != nullptr && thisIteration) {
502 runOnceCallbacks_->push_back(*callback);
504 loopCallbacks_.push_back(*callback);
508 void EventBase::runInLoop(const Cob& cob, bool thisIteration) {
509 DCHECK(isInEventBaseThread());
510 auto wrapper = new FunctionLoopCallback<Cob>(cob);
511 wrapper->context_ = RequestContext::saveContext();
512 if (runOnceCallbacks_ != nullptr && thisIteration) {
513 runOnceCallbacks_->push_back(*wrapper);
515 loopCallbacks_.push_back(*wrapper);
519 void EventBase::runInLoop(Cob&& cob, bool thisIteration) {
520 DCHECK(isInEventBaseThread());
521 auto wrapper = new FunctionLoopCallback<Cob>(std::move(cob));
522 wrapper->context_ = RequestContext::saveContext();
523 if (runOnceCallbacks_ != nullptr && thisIteration) {
524 runOnceCallbacks_->push_back(*wrapper);
526 loopCallbacks_.push_back(*wrapper);
530 void EventBase::runOnDestruction(LoopCallback* callback) {
531 std::lock_guard<std::mutex> lg(onDestructionCallbacksMutex_);
532 callback->cancelLoopCallback();
533 onDestructionCallbacks_.push_back(*callback);
536 void EventBase::runBeforeLoop(LoopCallback* callback) {
537 DCHECK(isInEventBaseThread());
538 callback->cancelLoopCallback();
539 runBeforeLoopCallbacks_.push_back(*callback);
542 bool EventBase::runInEventBaseThread(void (*fn)(void*), void* arg) {
544 // It will be received by the FunctionRunner in the EventBase's thread.
546 // We try not to schedule nullptr callbacks
548 LOG(ERROR) << "EventBase " << this
549 << ": Scheduling nullptr callbacks is not allowed";
553 // Short-circuit if we are already in our event base
554 if (inRunningEventBaseThread()) {
555 runInLoop(new RunInLoopCallback(fn, arg));
561 queue_->putMessage(std::make_pair(fn, arg));
562 } catch (const std::exception& ex) {
563 LOG(ERROR) << "EventBase " << this << ": failed to schedule function "
564 << fn << "for EventBase thread: " << ex.what();
571 bool EventBase::runInEventBaseThread(const Cob& fn) {
572 // Short-circuit if we are already in our event base
573 if (inRunningEventBaseThread()) {
579 // Allocate a copy of the function so we can pass it to the other thread
580 // The other thread will delete this copy once the function has been run
582 fnCopy = new Cob(fn);
583 } catch (const std::bad_alloc& ex) {
584 LOG(ERROR) << "failed to allocate tr::function copy "
585 << "for runInEventBaseThread()";
589 if (!runInEventBaseThread(&EventBase::runFunctionPtr, fnCopy)) {
597 bool EventBase::runInEventBaseThreadAndWait(const Cob& fn) {
598 if (inRunningEventBaseThread()) {
599 LOG(ERROR) << "EventBase " << this << ": Waiting in the event loop is not "
606 std::condition_variable cv;
607 runInEventBaseThread([&] {
609 std::unique_lock<std::mutex> l(m);
612 // We cannot release the lock before notify_one, because a spurious
613 // wakeup in the waiting thread may lead to cv and m going out of scope
618 std::unique_lock<std::mutex> l(m);
619 cv.wait(l, [&] { return ready; });
624 bool EventBase::runImmediatelyOrRunInEventBaseThreadAndWait(const Cob& fn) {
625 if (isInEventBaseThread()) {
629 return runInEventBaseThreadAndWait(fn);
633 void EventBase::runAfterDelay(const Cob& cob,
635 TimeoutManager::InternalEnum in) {
636 if (!tryRunAfterDelay(cob, milliseconds, in)) {
637 folly::throwSystemError(
638 "error in EventBase::runAfterDelay(), failed to schedule timeout");
642 bool EventBase::tryRunAfterDelay(const Cob& cob,
644 TimeoutManager::InternalEnum in) {
645 CobTimeout* timeout = new CobTimeout(this, cob, in);
646 if (!timeout->scheduleTimeout(milliseconds)) {
650 pendingCobTimeouts_.push_back(*timeout);
654 bool EventBase::runLoopCallbacks(bool setContext) {
655 if (!loopCallbacks_.empty()) {
657 // Swap the loopCallbacks_ list with a temporary list on our stack.
658 // This way we will only run callbacks scheduled at the time
659 // runLoopCallbacks() was invoked.
661 // If any of these callbacks in turn call runInLoop() to schedule more
662 // callbacks, those new callbacks won't be run until the next iteration
663 // around the event loop. This prevents runInLoop() callbacks from being
664 // able to start file descriptor and timeout based events.
665 LoopCallbackList currentCallbacks;
666 currentCallbacks.swap(loopCallbacks_);
667 runOnceCallbacks_ = ¤tCallbacks;
669 while (!currentCallbacks.empty()) {
670 LoopCallback* callback = ¤tCallbacks.front();
671 currentCallbacks.pop_front();
673 RequestContext::setContext(callback->context_);
675 callback->runLoopCallback();
678 runOnceCallbacks_ = nullptr;
684 void EventBase::initNotificationQueue() {
685 // Infinite size queue
686 queue_.reset(new NotificationQueue<std::pair<void (*)(void*), void*>>());
688 // We allocate fnRunner_ separately, rather than declaring it directly
689 // as a member of EventBase solely so that we don't need to include
690 // NotificationQueue.h from EventBase.h
691 fnRunner_.reset(new FunctionRunner());
693 // Mark this as an internal event, so event_base_loop() will return if
694 // there are no other events besides this one installed.
696 // Most callers don't care about the internal notification queue used by
697 // EventBase. The queue is always installed, so if we did count the queue as
698 // an active event, loop() would never exit with no more events to process.
699 // Users can use loopForever() if they do care about the notification queue.
700 // (This is useful for EventBase threads that do nothing but process
701 // runInEventBaseThread() notifications.)
702 fnRunner_->startConsumingInternal(this, queue_.get());
705 void EventBase::SmoothLoopTime::setTimeInterval(uint64_t timeInterval) {
706 expCoeff_ = -1.0/timeInterval;
707 VLOG(11) << "expCoeff_ " << expCoeff_ << " " << __PRETTY_FUNCTION__;
710 void EventBase::SmoothLoopTime::reset(double value) {
714 void EventBase::SmoothLoopTime::addSample(int64_t idle, int64_t busy) {
716 * Position at which the busy sample is considered to be taken.
717 * (Allows to quickly skew our average without editing much code)
719 enum BusySamplePosition {
720 RIGHT = 0, // busy sample placed at the end of the iteration
721 CENTER = 1, // busy sample placed at the middle point of the iteration
722 LEFT = 2, // busy sample placed at the beginning of the iteration
725 // See http://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
726 // and D676020 for more info on this calculation.
727 VLOG(11) << "idle " << idle << " oldBusyLeftover_ " << oldBusyLeftover_ <<
728 " idle + oldBusyLeftover_ " << idle + oldBusyLeftover_ <<
729 " busy " << busy << " " << __PRETTY_FUNCTION__;
730 idle += oldBusyLeftover_ + busy;
731 oldBusyLeftover_ = (busy * BusySamplePosition::CENTER) / 2;
732 idle -= oldBusyLeftover_;
734 double coeff = exp(idle * expCoeff_);
736 value_ += (1.0 - coeff) * busy;
739 bool EventBase::nothingHandledYet() {
740 VLOG(11) << "latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
741 return (nextLoopCnt_ != latestLoopCnt_);
745 void EventBase::runFunctionPtr(Cob* fn) {
746 // The function should never throw an exception, because we have no
747 // way of knowing what sort of error handling to perform.
749 // If it does throw, log a message and abort the program.
752 } catch (const std::exception &ex) {
753 LOG(ERROR) << "runInEventBaseThread() std::function threw a "
754 << typeid(ex).name() << " exception: " << ex.what();
757 LOG(ERROR) << "runInEventBaseThread() std::function threw an exception";
761 // The function object was allocated by runInEventBaseThread().
762 // Delete it once it has been run.
766 EventBase::RunInLoopCallback::RunInLoopCallback(void (*fn)(void*), void* arg)
770 void EventBase::RunInLoopCallback::runLoopCallback() noexcept {
775 void EventBase::attachTimeoutManager(AsyncTimeout* obj,
776 InternalEnum internal) {
778 struct event* ev = obj->getEvent();
779 assert(ev->ev_base == nullptr);
781 event_base_set(getLibeventBase(), ev);
782 if (internal == AsyncTimeout::InternalEnum::INTERNAL) {
783 // Set the EVLIST_INTERNAL flag
784 ev->ev_flags |= EVLIST_INTERNAL;
788 void EventBase::detachTimeoutManager(AsyncTimeout* obj) {
790 struct event* ev = obj->getEvent();
791 ev->ev_base = nullptr;
794 bool EventBase::scheduleTimeout(AsyncTimeout* obj,
795 TimeoutManager::timeout_type timeout) {
796 assert(isInEventBaseThread());
797 // Set up the timeval and add the event
799 tv.tv_sec = timeout.count() / 1000LL;
800 tv.tv_usec = (timeout.count() % 1000LL) * 1000LL;
802 struct event* ev = obj->getEvent();
803 if (event_add(ev, &tv) < 0) {
804 LOG(ERROR) << "EventBase: failed to schedule timeout: " << strerror(errno);
811 void EventBase::cancelTimeout(AsyncTimeout* obj) {
812 assert(isInEventBaseThread());
813 struct event* ev = obj->getEvent();
814 if (EventUtil::isEventRegistered(ev)) {
819 void EventBase::setName(const std::string& name) {
820 assert(isInEventBaseThread());
824 setThreadName(loopThread_.load(std::memory_order_relaxed),
829 const std::string& EventBase::getName() {
830 assert(isInEventBaseThread());
834 const char* EventBase::getLibeventVersion() { return event_get_version(); }
835 const char* EventBase::getLibeventMethod() { return event_get_method(); }