/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2016 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#include <folly/ThreadName.h>
#include <folly/io/async/NotificationQueue.h>
+#include <folly/portability/Unistd.h>
-#include <boost/static_assert.hpp>
#include <condition_variable>
#include <fcntl.h>
#include <mutex>
#include <pthread.h>
-#include <unistd.h>
namespace {
-using folly::Cob;
using folly::EventBase;
-template <typename Callback>
class FunctionLoopCallback : public EventBase::LoopCallback {
public:
- explicit FunctionLoopCallback(Cob&& function)
+ explicit FunctionLoopCallback(EventBase::Func&& function)
: function_(std::move(function)) {}
- explicit FunctionLoopCallback(const Cob& function)
- : function_(function) {}
-
- virtual void runLoopCallback() noexcept {
+ void runLoopCallback() noexcept override {
function_();
delete this;
}
private:
- Callback function_;
+ EventBase::Func function_;
};
-
}
namespace folly {
-const int kNoFD = -1;
-
/*
* EventBase::FunctionRunner
*/
class EventBase::FunctionRunner
- : public NotificationQueue<std::pair<void (*)(void*), void*>>::Consumer {
+ : public NotificationQueue<EventBase::Func>::Consumer {
public:
- void messageAvailable(std::pair<void (*)(void*), void*>&& msg) {
-
+ void messageAvailable(Func&& msg) override {
// In libevent2, internal events do not break the loop.
// Most users would expect loop(), followed by runInEventBaseThread(),
// to break the loop and check if it should exit or not.
// stop_ flag as well as runInLoop callbacks, etc.
event_base_loopbreak(getEventBase()->evb_);
- if (msg.first == nullptr && msg.second == nullptr) {
+ if (!msg) {
// terminateLoopSoon() sends a null message just to
// wake up the loop. We can ignore these messages.
return;
}
- // If function is nullptr, just log and move on
- if (!msg.first) {
- LOG(ERROR) << "nullptr callback registered to be run in "
- << "event base thread";
- return;
- }
-
// The function should never throw an exception, because we have no
// way of knowing what sort of error handling to perform.
//
// If it does throw, log a message and abort the program.
try {
- msg.first(msg.second);
+ msg();
} catch (const std::exception& ex) {
LOG(ERROR) << "runInEventBaseThread() function threw a "
<< typeid(ex).name() << " exception: " << ex.what();
* EventBase methods
*/
-EventBase::EventBase()
+EventBase::EventBase(bool enableTimeMeasurement)
: runOnceCallbacks_(nullptr)
, stop_(false)
- , loopThread_(0)
+ , loopThread_()
, queue_(nullptr)
, fnRunner_(nullptr)
, maxLatency_(0)
, avgLoopTime_(2000000)
, maxLatencyLoopTime_(avgLoopTime_)
+ , enableTimeMeasurement_(enableTimeMeasurement)
, nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
, latestLoopCnt_(nextLoopCnt_)
, startWork_(0)
, observer_(nullptr)
- , observerSampleCount_(0) {
+ , observerSampleCount_(0)
+ , executionObserver_(nullptr) {
+ struct event ev;
{
std::lock_guard<std::mutex> lock(libevent_mutex_);
// allowing examination of its value without an explicit reference here.
// If ev.ev_base is NULL, then event_init() must be called, otherwise
// call event_base_new().
- struct event ev;
event_set(&ev, 0, 0, nullptr, nullptr);
- evb_ = (ev.ev_base) ? event_base_new() : event_init();
+ if (!ev.ev_base) {
+ evb_ = event_init();
+ }
+ }
+
+ if (ev.ev_base) {
+ evb_ = event_base_new();
}
+
if (UNLIKELY(evb_ == nullptr)) {
LOG(ERROR) << "EventBase(): Failed to init event base.";
folly::throwSystemError("error in EventBase::EventBase()");
}
VLOG(5) << "EventBase(): Created.";
initNotificationQueue();
- RequestContext::getStaticContext();
+ RequestContext::saveContext();
}
// takes ownership of the event_base
-EventBase::EventBase(event_base* evb)
+EventBase::EventBase(event_base* evb, bool enableTimeMeasurement)
: runOnceCallbacks_(nullptr)
, stop_(false)
- , loopThread_(0)
+ , loopThread_()
, evb_(evb)
, queue_(nullptr)
, fnRunner_(nullptr)
, maxLatency_(0)
, avgLoopTime_(2000000)
, maxLatencyLoopTime_(avgLoopTime_)
+ , enableTimeMeasurement_(enableTimeMeasurement)
, nextLoopCnt_(-40) // Early wrap-around so bugs will manifest soon
, latestLoopCnt_(nextLoopCnt_)
, startWork_(0)
, observer_(nullptr)
- , observerSampleCount_(0) {
+ , observerSampleCount_(0)
+ , executionObserver_(nullptr) {
if (UNLIKELY(evb_ == nullptr)) {
LOG(ERROR) << "EventBase(): Pass nullptr as event base.";
throw std::invalid_argument("EventBase(): event base cannot be nullptr");
}
initNotificationQueue();
- RequestContext::getStaticContext();
+ RequestContext::saveContext();
}
EventBase::~EventBase() {
+ // Keep looping until all keep-alive handles are released. Each keep-alive
+ // handle signals that some external code will still schedule some work on
+ // this EventBase (so it's not safe to destroy it).
+ while (loopKeepAliveCount_ > 0) {
+ applyLoopKeepAlive();
+ loopOnce();
+ }
+
// Call all destruction callbacks, before we start cleaning up our state.
while (!onDestructionCallbacks_.empty()) {
LoopCallback* callback = &onDestructionCallbacks_.front();
delete &runBeforeLoopCallbacks_.front();
}
- (void) runLoopCallbacks(false);
+ (void)runLoopCallbacks();
if (!fnRunner_->consumeUntilDrained()) {
LOG(ERROR) << "~EventBase(): Unable to drain notification queue";
std::lock_guard<std::mutex> lock(libevent_mutex_);
event_base_free(evb_);
}
+
+ {
+ std::lock_guard<std::mutex> lock(localStorageMutex_);
+ for (auto storage : localStorageToDtor_) {
+ storage->onEventBaseDestruction(*this);
+ }
+ }
VLOG(5) << "EventBase(): Destroyed.";
}
// Set smoothing coefficient for loop load average; input is # of milliseconds
// for exp(-1) decay.
void EventBase::setLoadAvgMsec(uint32_t ms) {
+ assert(enableTimeMeasurement_);
uint64_t us = 1000 * ms;
if (ms > 0) {
maxLatencyLoopTime_.setTimeInterval(us);
}
void EventBase::resetLoadAvg(double value) {
+ assert(enableTimeMeasurement_);
avgLoopTime_.reset(value);
maxLatencyLoopTime_.reset(value);
}
bool EventBase::loopBody(int flags) {
VLOG(5) << "EventBase(): Starting loop.";
+
+ DCHECK(!invokingLoop_)
+ << "Your code just tried to loop over an event base from inside another "
+ << "event base loop. Since libevent is not reentrant, this leads to "
+ << "undefined behavior in opt builds. Please fix immediately. For the "
+ << "common case of an inner function that needs to do some synchronous "
+ << "computation on an event-base, replace getEventBase() by a new, "
+ << "stack-allocated EvenBase.";
+ invokingLoop_ = true;
+ SCOPE_EXIT {
+ invokingLoop_ = false;
+ };
+
int res = 0;
bool ranLoopCallbacks;
bool blocking = !(flags & EVLOOP_NONBLOCK);
bool once = (flags & EVLOOP_ONCE);
+ // time-measurement variables.
+ std::chrono::steady_clock::time_point prev;
+ int64_t idleStart = 0;
+ int64_t busy;
+ int64_t idle;
+
loopThread_.store(pthread_self(), std::memory_order_release);
if (!name_.empty()) {
setThreadName(name_);
}
- auto prev = std::chrono::steady_clock::now();
- int64_t idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
- std::chrono::steady_clock::now().time_since_epoch()).count();
+ if (enableTimeMeasurement_) {
+ prev = std::chrono::steady_clock::now();
+ idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
+ std::chrono::steady_clock::now().time_since_epoch()).count();
+ }
- // TODO: Read stop_ atomically with an acquire barrier.
- while (!stop_) {
+ while (!stop_.load(std::memory_order_acquire)) {
+ applyLoopKeepAlive();
++nextLoopCnt_;
// Run the before loop callbacks
ranLoopCallbacks = runLoopCallbacks();
- int64_t busy = std::chrono::duration_cast<std::chrono::microseconds>(
- std::chrono::steady_clock::now().time_since_epoch()).count() - startWork_;
- int64_t idle = startWork_ - idleStart;
+ if (enableTimeMeasurement_) {
+ busy = std::chrono::duration_cast<std::chrono::microseconds>(
+ std::chrono::steady_clock::now().time_since_epoch()).count() -
+ startWork_;
+ idle = startWork_ - idleStart;
- avgLoopTime_.addSample(idle, busy);
- maxLatencyLoopTime_.addSample(idle, busy);
+ avgLoopTime_.addSample(idle, busy);
+ maxLatencyLoopTime_.addSample(idle, busy);
- if (observer_) {
- if (observerSampleCount_++ == observer_->getSampleRate()) {
- observerSampleCount_ = 0;
- observer_->loopSample(busy, idle);
+ if (observer_) {
+ if (observerSampleCount_++ == observer_->getSampleRate()) {
+ observerSampleCount_ = 0;
+ observer_->loopSample(busy, idle);
+ }
}
- }
- VLOG(11) << "EventBase " << this << " did not timeout "
- " loop time guess: " << busy + idle <<
- " idle time: " << idle <<
- " busy time: " << busy <<
- " avgLoopTime: " << avgLoopTime_.get() <<
- " maxLatencyLoopTime: " << maxLatencyLoopTime_.get() <<
- " maxLatency_: " << maxLatency_ <<
- " nothingHandledYet(): "<< nothingHandledYet();
-
- // see if our average loop time has exceeded our limit
- if ((maxLatency_ > 0) &&
- (maxLatencyLoopTime_.get() > double(maxLatency_))) {
- maxLatencyCob_();
- // back off temporarily -- don't keep spamming maxLatencyCob_
- // if we're only a bit over the limit
- maxLatencyLoopTime_.dampen(0.9);
- }
+ VLOG(11) << "EventBase " << this << " did not timeout "
+ " loop time guess: " << busy + idle <<
+ " idle time: " << idle <<
+ " busy time: " << busy <<
+ " avgLoopTime: " << avgLoopTime_.get() <<
+ " maxLatencyLoopTime: " << maxLatencyLoopTime_.get() <<
+ " maxLatency_: " << maxLatency_ <<
+ " notificationQueueSize: " << getNotificationQueueSize() <<
+ " nothingHandledYet(): "<< nothingHandledYet();
+
+ // see if our average loop time has exceeded our limit
+ if ((maxLatency_ > 0) &&
+ (maxLatencyLoopTime_.get() > double(maxLatency_))) {
+ maxLatencyCob_();
+ // back off temporarily -- don't keep spamming maxLatencyCob_
+ // if we're only a bit over the limit
+ maxLatencyLoopTime_.dampen(0.9);
+ }
- // Our loop run did real work; reset the idle timer
- idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
- std::chrono::steady_clock::now().time_since_epoch()).count();
+ // Our loop run did real work; reset the idle timer
+ idleStart = std::chrono::duration_cast<std::chrono::microseconds>(
+ std::chrono::steady_clock::now().time_since_epoch()).count();
+ } else {
+ VLOG(11) << "EventBase " << this << " did not timeout";
+ }
// If the event loop indicate that there were no more events, and
// we also didn't have any loop callbacks to run, there is nothing left to
}
}
- VLOG(5) << "EventBase " << this << " loop time: " <<
- getTimeDelta(&prev).count();
+ if (enableTimeMeasurement_) {
+ VLOG(5) << "EventBase " << this << " loop time: " <<
+ getTimeDelta(&prev).count();
+ }
if (once) {
break;
return false;
}
- loopThread_.store(0, std::memory_order_release);
+ loopThread_.store({}, std::memory_order_release);
VLOG(5) << "EventBase(): Done with loop.";
return true;
}
-void EventBase::loopForever() {
- // Update the notification queue event to treat it as a normal (non-internal)
- // event. The notification queue event always remains installed, and the main
- // loop won't exit with it installed.
- fnRunner_->stopConsuming();
- fnRunner_->startConsuming(this, queue_.get());
-
- bool ret = loop();
+void EventBase::applyLoopKeepAlive() {
+ if (loopKeepAliveActive_ && loopKeepAliveCount_ == 0) {
+ // Restore the notification queue internal flag
+ fnRunner_->stopConsuming();
+ fnRunner_->startConsumingInternal(this, queue_.get());
+ loopKeepAliveActive_ = false;
+ } else if (!loopKeepAliveActive_ && loopKeepAliveCount_ > 0) {
+ // Update the notification queue event to treat it as a normal
+ // (non-internal) event. The notification queue event always remains
+ // installed, and the main loop won't exit with it installed.
+ fnRunner_->stopConsuming();
+ fnRunner_->startConsuming(this, queue_.get());
+ loopKeepAliveActive_ = true;
+ }
+}
- // Restore the notification queue internal flag
- fnRunner_->stopConsuming();
- fnRunner_->startConsumingInternal(this, queue_.get());
+void EventBase::loopForever() {
+ bool ret;
+ {
+ SCOPE_EXIT {
+ applyLoopKeepAlive();
+ };
+ // Make sure notification queue events are treated as normal events.
+ auto keepAlive = loopKeepAlive();
+ ret = loop();
+ }
if (!ret) {
folly::throwSystemError("error in EventBase::loopForever()");
}
}
-bool EventBase::bumpHandlingTime() {
+void EventBase::bumpHandlingTime() {
+ if (!enableTimeMeasurement_) {
+ return;
+ }
+
VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
" (loop) latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
- if(nothingHandledYet()) {
+ if (nothingHandledYet()) {
latestLoopCnt_ = nextLoopCnt_;
// set the time
startWork_ = std::chrono::duration_cast<std::chrono::microseconds>(
- std::chrono::steady_clock::now().time_since_epoch()).count();
+ std::chrono::steady_clock::now().time_since_epoch())
+ .count();
- VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__ <<
- " (loop) startWork_ " << startWork_;
- return true;
+ VLOG(11) << "EventBase " << this << " " << __PRETTY_FUNCTION__
+ << " (loop) startWork_ " << startWork_;
}
- return false;
}
void EventBase::terminateLoopSoon() {
// this likely means the EventBase already has lots of events waiting
// anyway.
try {
- queue_->putMessage(std::make_pair(nullptr, nullptr));
+ queue_->putMessage(nullptr);
} catch (...) {
// We don't care if putMessage() fails. This likely means
// the EventBase already has lots of events waiting anyway.
}
}
-void EventBase::runInLoop(const Cob& cob, bool thisIteration) {
- DCHECK(isInEventBaseThread());
- auto wrapper = new FunctionLoopCallback<Cob>(cob);
- wrapper->context_ = RequestContext::saveContext();
- if (runOnceCallbacks_ != nullptr && thisIteration) {
- runOnceCallbacks_->push_back(*wrapper);
- } else {
- loopCallbacks_.push_back(*wrapper);
- }
-}
-
-void EventBase::runInLoop(Cob&& cob, bool thisIteration) {
+void EventBase::runInLoop(Func cob, bool thisIteration) {
DCHECK(isInEventBaseThread());
- auto wrapper = new FunctionLoopCallback<Cob>(std::move(cob));
+ auto wrapper = new FunctionLoopCallback(std::move(cob));
wrapper->context_ = RequestContext::saveContext();
if (runOnceCallbacks_ != nullptr && thisIteration) {
runOnceCallbacks_->push_back(*wrapper);
}
void EventBase::runOnDestruction(LoopCallback* callback) {
- DCHECK(isInEventBaseThread());
+ std::lock_guard<std::mutex> lg(onDestructionCallbacksMutex_);
callback->cancelLoopCallback();
onDestructionCallbacks_.push_back(*callback);
}
runBeforeLoopCallbacks_.push_back(*callback);
}
-bool EventBase::runInEventBaseThread(void (*fn)(void*), void* arg) {
+bool EventBase::runInEventBaseThread(Func fn) {
// Send the message.
// It will be received by the FunctionRunner in the EventBase's thread.
// Short-circuit if we are already in our event base
if (inRunningEventBaseThread()) {
- runInLoop(new RunInLoopCallback(fn, arg));
+ runInLoop(std::move(fn));
return true;
}
try {
- queue_->putMessage(std::make_pair(fn, arg));
+ queue_->putMessage(std::move(fn));
} catch (const std::exception& ex) {
LOG(ERROR) << "EventBase " << this << ": failed to schedule function "
- << fn << "for EventBase thread: " << ex.what();
- return false;
- }
-
- return true;
-}
-
-bool EventBase::runInEventBaseThread(const Cob& fn) {
- // Short-circuit if we are already in our event base
- if (inRunningEventBaseThread()) {
- runInLoop(fn);
- return true;
- }
-
- Cob* fnCopy;
- // Allocate a copy of the function so we can pass it to the other thread
- // The other thread will delete this copy once the function has been run
- try {
- fnCopy = new Cob(fn);
- } catch (const std::bad_alloc& ex) {
- LOG(ERROR) << "failed to allocate tr::function copy "
- << "for runInEventBaseThread()";
- return false;
- }
-
- if (!runInEventBaseThread(&EventBase::runFunctionPtr, fnCopy)) {
- delete fnCopy;
+ << "for EventBase thread: " << ex.what();
return false;
}
return true;
}
-bool EventBase::runInEventBaseThreadAndWait(void (*fn)(void*), void* arg) {
+bool EventBase::runInEventBaseThreadAndWait(Func fn) {
if (inRunningEventBaseThread()) {
LOG(ERROR) << "EventBase " << this << ": Waiting in the event loop is not "
<< "allowed";
SCOPE_EXIT {
std::unique_lock<std::mutex> l(m);
ready = true;
- l.unlock();
cv.notify_one();
+ // We cannot release the lock before notify_one, because a spurious
+ // wakeup in the waiting thread may lead to cv and m going out of scope
+ // prematurely.
};
- fn(arg);
+ fn();
});
std::unique_lock<std::mutex> l(m);
cv.wait(l, [&] { return ready; });
return true;
}
-bool EventBase::runInEventBaseThreadAndWait(const Cob& fn) {
- if (inRunningEventBaseThread()) {
- LOG(ERROR) << "EventBase " << this << ": Waiting in the event loop is not "
- << "allowed";
- return false;
+bool EventBase::runImmediatelyOrRunInEventBaseThreadAndWait(Func fn) {
+ if (isInEventBaseThread()) {
+ fn();
+ return true;
+ } else {
+ return runInEventBaseThreadAndWait(std::move(fn));
}
+}
- bool ready = false;
- std::mutex m;
- std::condition_variable cv;
- runInEventBaseThread([&] {
- SCOPE_EXIT {
- std::unique_lock<std::mutex> l(m);
- ready = true;
- l.unlock();
- cv.notify_one();
- };
- fn();
- });
- std::unique_lock<std::mutex> l(m);
- cv.wait(l, [&] { return ready; });
-
- return true;
+void EventBase::runAfterDelay(
+ Func cob,
+ uint32_t milliseconds,
+ TimeoutManager::InternalEnum in) {
+ if (!tryRunAfterDelay(std::move(cob), milliseconds, in)) {
+ folly::throwSystemError(
+ "error in EventBase::runAfterDelay(), failed to schedule timeout");
+ }
}
-bool EventBase::runAfterDelay(const Cob& cob,
- int milliseconds,
- TimeoutManager::InternalEnum in) {
- CobTimeout* timeout = new CobTimeout(this, cob, in);
+bool EventBase::tryRunAfterDelay(
+ Func cob,
+ uint32_t milliseconds,
+ TimeoutManager::InternalEnum in) {
+ CobTimeout* timeout = new CobTimeout(this, std::move(cob), in);
if (!timeout->scheduleTimeout(milliseconds)) {
delete timeout;
return false;
}
-
pendingCobTimeouts_.push_back(*timeout);
return true;
}
-bool EventBase::runLoopCallbacks(bool setContext) {
+bool EventBase::runLoopCallbacks() {
if (!loopCallbacks_.empty()) {
bumpHandlingTime();
// Swap the loopCallbacks_ list with a temporary list on our stack.
while (!currentCallbacks.empty()) {
LoopCallback* callback = ¤tCallbacks.front();
currentCallbacks.pop_front();
- if (setContext) {
- RequestContext::setContext(callback->context_);
- }
+ folly::RequestContextScopeGuard rctx(callback->context_);
callback->runLoopCallback();
}
void EventBase::initNotificationQueue() {
// Infinite size queue
- queue_.reset(new NotificationQueue<std::pair<void (*)(void*), void*>>());
+ queue_.reset(new NotificationQueue<Func>());
// We allocate fnRunner_ separately, rather than declaring it directly
// as a member of EventBase solely so that we don't need to include
value_ += (1.0 - coeff) * busy;
}
-bool EventBase::nothingHandledYet() {
+bool EventBase::nothingHandledYet() const noexcept {
VLOG(11) << "latest " << latestLoopCnt_ << " next " << nextLoopCnt_;
return (nextLoopCnt_ != latestLoopCnt_);
}
-/* static */
-void EventBase::runFunctionPtr(Cob* fn) {
- // The function should never throw an exception, because we have no
- // way of knowing what sort of error handling to perform.
- //
- // If it does throw, log a message and abort the program.
- try {
- (*fn)();
- } catch (const std::exception &ex) {
- LOG(ERROR) << "runInEventBaseThread() std::function threw a "
- << typeid(ex).name() << " exception: " << ex.what();
- abort();
- } catch (...) {
- LOG(ERROR) << "runInEventBaseThread() std::function threw an exception";
- abort();
- }
-
- // The function object was allocated by runInEventBaseThread().
- // Delete it once it has been run.
- delete fn;
-}
-
-EventBase::RunInLoopCallback::RunInLoopCallback(void (*fn)(void*), void* arg)
- : fn_(fn)
- , arg_(arg) {}
-
-void EventBase::RunInLoopCallback::runLoopCallback() noexcept {
- fn_(arg_);
- delete this;
-}
-
void EventBase::attachTimeoutManager(AsyncTimeout* obj,
InternalEnum internal) {
event_base_set(getLibeventBase(), ev);
if (internal == AsyncTimeout::InternalEnum::INTERNAL) {
// Set the EVLIST_INTERNAL flag
- ev->ev_flags |= EVLIST_INTERNAL;
+ event_ref_flags(ev) |= EVLIST_INTERNAL;
}
}
}
bool EventBase::scheduleTimeout(AsyncTimeout* obj,
- std::chrono::milliseconds timeout) {
+ TimeoutManager::timeout_type timeout) {
assert(isInEventBaseThread());
// Set up the timeval and add the event
struct timeval tv;
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