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- /*
- * Copyright 2016-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #include <folly/experimental/observer/detail/ObserverManager.h>
- #include <folly/ExceptionString.h>
- #include <folly/Format.h>
- #include <folly/MPMCQueue.h>
- #include <folly/Range.h>
- #include <folly/Singleton.h>
- #include <folly/portability/GFlags.h>
- #include <folly/system/ThreadName.h>
- namespace folly {
- namespace observer_detail {
- FOLLY_TLS bool ObserverManager::inManagerThread_{false};
- FOLLY_TLS ObserverManager::DependencyRecorder::Dependencies*
- ObserverManager::DependencyRecorder::currentDependencies_{nullptr};
- DEFINE_int32(
- observer_manager_pool_size,
- 4,
- "How many internal threads ObserverManager should use");
- static constexpr StringPiece kObserverManagerThreadNamePrefix{"ObserverMngr"};
- namespace {
- constexpr size_t kCurrentQueueSize{10 * 1024};
- constexpr size_t kNextQueueSize{10 * 1024};
- } // namespace
- class ObserverManager::CurrentQueue {
- public:
- CurrentQueue() : queue_(kCurrentQueueSize) {
- if (FLAGS_observer_manager_pool_size < 1) {
- LOG(ERROR) << "--observer_manager_pool_size should be >= 1";
- FLAGS_observer_manager_pool_size = 1;
- }
- for (int32_t i = 0; i < FLAGS_observer_manager_pool_size; ++i) {
- threads_.emplace_back([this, i]() {
- folly::setThreadName(
- folly::sformat("{}{}", kObserverManagerThreadNamePrefix, i));
- ObserverManager::inManagerThread_ = true;
- while (true) {
- Function<void()> task;
- queue_.blockingRead(task);
- if (!task) {
- return;
- }
- try {
- task();
- } catch (...) {
- LOG(ERROR) << "Exception while running CurrentQueue task: "
- << exceptionStr(std::current_exception());
- }
- }
- });
- }
- }
- ~CurrentQueue() {
- for (size_t i = 0; i < threads_.size(); ++i) {
- queue_.blockingWrite(nullptr);
- }
- for (auto& thread : threads_) {
- thread.join();
- }
- CHECK(queue_.isEmpty());
- }
- void add(Function<void()> task) {
- if (ObserverManager::inManagerThread()) {
- if (!queue_.write(std::move(task))) {
- throw std::runtime_error("Too many Observers scheduled for update.");
- }
- } else {
- queue_.blockingWrite(std::move(task));
- }
- }
- private:
- MPMCQueue<Function<void()>> queue_;
- std::vector<std::thread> threads_;
- };
- class ObserverManager::NextQueue {
- public:
- explicit NextQueue(ObserverManager& manager)
- : manager_(manager), queue_(kNextQueueSize) {
- thread_ = std::thread([&]() {
- Core::WeakPtr queueCoreWeak;
- while (true) {
- queue_.blockingRead(queueCoreWeak);
- if (stop_) {
- return;
- }
- std::vector<Core::Ptr> cores;
- {
- auto queueCore = queueCoreWeak.lock();
- if (!queueCore) {
- continue;
- }
- cores.emplace_back(std::move(queueCore));
- }
- {
- SharedMutexReadPriority::WriteHolder wh(manager_.versionMutex_);
- // We can't pick more tasks from the queue after we bumped the
- // version, so we have to do this while holding the lock.
- while (cores.size() < kNextQueueSize && queue_.read(queueCoreWeak)) {
- if (stop_) {
- return;
- }
- if (auto queueCore = queueCoreWeak.lock()) {
- cores.emplace_back(std::move(queueCore));
- }
- }
- ++manager_.version_;
- }
- for (auto& core : cores) {
- manager_.scheduleRefresh(std::move(core), manager_.version_, true);
- }
- }
- });
- }
- void add(Core::WeakPtr core) {
- queue_.blockingWrite(std::move(core));
- }
- ~NextQueue() {
- stop_ = true;
- // Write to the queue to notify the thread.
- queue_.blockingWrite(Core::WeakPtr());
- thread_.join();
- }
- private:
- ObserverManager& manager_;
- MPMCQueue<Core::WeakPtr> queue_;
- std::thread thread_;
- std::atomic<bool> stop_{false};
- };
- ObserverManager::ObserverManager() {
- currentQueue_ = std::make_unique<CurrentQueue>();
- nextQueue_ = std::make_unique<NextQueue>(*this);
- }
- ObserverManager::~ObserverManager() {
- // Destroy NextQueue, before the rest of this object, since it expects
- // ObserverManager to be alive.
- nextQueue_.reset();
- currentQueue_.reset();
- }
- void ObserverManager::scheduleCurrent(Function<void()> task) {
- currentQueue_->add(std::move(task));
- }
- void ObserverManager::scheduleNext(Core::WeakPtr core) {
- nextQueue_->add(std::move(core));
- }
- struct ObserverManager::Singleton {
- static folly::Singleton<ObserverManager> instance;
- // MSVC 2015 doesn't let us access ObserverManager's constructor if we
- // try to use a lambda to initialize instance, so we have to create
- // an actual function instead.
- static ObserverManager* createManager() {
- return new ObserverManager();
- }
- };
- folly::Singleton<ObserverManager> ObserverManager::Singleton::instance(
- createManager);
- std::shared_ptr<ObserverManager> ObserverManager::getInstance() {
- return Singleton::instance.try_get();
- }
- } // namespace observer_detail
- } // namespace folly
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