2 * Copyright 2016 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.
16 #include <folly/experimental/observer/detail/ObserverManager.h>
18 #include <folly/MPMCQueue.h>
19 #include <folly/Singleton.h>
22 namespace observer_detail {
24 FOLLY_TLS bool ObserverManager::inManagerThread_{false};
25 FOLLY_TLS ObserverManager::DependencyRecorder::Dependencies*
26 ObserverManager::DependencyRecorder::currentDependencies_{nullptr};
29 observer_manager_pool_size,
31 "How many internal threads ObserverManager should use");
34 constexpr size_t kCurrentQueueSize{10 * 1024};
35 constexpr size_t kNextQueueSize{10 * 1024};
38 class ObserverManager::CurrentQueue {
40 CurrentQueue() : queue_(kCurrentQueueSize) {
41 if (FLAGS_observer_manager_pool_size < 1) {
42 LOG(ERROR) << "--observer_manager_pool_size should be >= 1";
43 FLAGS_observer_manager_pool_size = 1;
45 for (int32_t i = 0; i < FLAGS_observer_manager_pool_size; ++i) {
46 threads_.emplace_back([&]() {
47 ObserverManager::inManagerThread_ = true;
50 Function<void()> task;
51 queue_.blockingRead(task);
60 LOG(ERROR) << "Exception while running CurrentQueue task: "
61 << exceptionStr(std::current_exception());
69 for (size_t i = 0; i < threads_.size(); ++i) {
70 queue_.blockingWrite(nullptr);
73 for (auto& thread : threads_) {
77 CHECK(queue_.isEmpty());
80 void add(Function<void()> task) {
81 if (ObserverManager::inManagerThread()) {
82 if (!queue_.write(std::move(task))) {
83 throw std::runtime_error("Too many Observers scheduled for update.");
86 queue_.blockingWrite(std::move(task));
91 MPMCQueue<Function<void()>> queue_;
92 std::vector<std::thread> threads_;
95 class ObserverManager::NextQueue {
97 explicit NextQueue(ObserverManager& manager)
98 : manager_(manager), queue_(kNextQueueSize) {
99 thread_ = std::thread([&]() {
103 queue_.blockingRead(queueCore);
109 std::vector<Core::Ptr> cores;
110 cores.emplace_back(std::move(queueCore));
113 SharedMutexReadPriority::WriteHolder wh(manager_.versionMutex_);
115 // We can't pick more tasks from the queue after we bumped the
116 // version, so we have to do this while holding the lock.
117 while (cores.size() < kNextQueueSize && queue_.read(queueCore)) {
121 cores.emplace_back(std::move(queueCore));
127 for (auto& core : cores) {
128 manager_.scheduleRefresh(std::move(core), manager_.version_, true);
134 void add(Core::Ptr core) {
135 queue_.blockingWrite(std::move(core));
139 // Emtpy element signals thread to terminate
140 queue_.blockingWrite(nullptr);
145 ObserverManager& manager_;
146 MPMCQueue<Core::Ptr> queue_;
150 ObserverManager::ObserverManager() {
151 currentQueue_ = make_unique<CurrentQueue>();
152 nextQueue_ = make_unique<NextQueue>(*this);
155 ObserverManager::~ObserverManager() {
156 // Destroy NextQueue, before the rest of this object, since it expects
157 // ObserverManager to be alive.
159 currentQueue_.reset();
162 void ObserverManager::scheduleCurrent(Function<void()> task) {
163 currentQueue_->add(std::move(task));
166 void ObserverManager::scheduleNext(Core::Ptr core) {
167 nextQueue_->add(std::move(core));
170 struct ObserverManager::Singleton {
171 static folly::Singleton<ObserverManager> instance;
172 // MSVC 2015 doesn't let us access ObserverManager's constructor if we
173 // try to use a lambda to initialize instance, so we have to create
174 // an actual function instead.
175 static ObserverManager* createManager() {
176 return new ObserverManager();
180 folly::Singleton<ObserverManager> ObserverManager::Singleton::instance(
183 std::shared_ptr<ObserverManager> ObserverManager::getInstance() {
184 return Singleton::instance.try_get();