2 * Copyright 2017 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/ExceptionString.h>
19 #include <folly/MPMCQueue.h>
20 #include <folly/Singleton.h>
21 #include <folly/portability/GFlags.h>
24 namespace observer_detail {
26 FOLLY_TLS bool ObserverManager::inManagerThread_{false};
27 FOLLY_TLS ObserverManager::DependencyRecorder::Dependencies*
28 ObserverManager::DependencyRecorder::currentDependencies_{nullptr};
31 observer_manager_pool_size,
33 "How many internal threads ObserverManager should use");
36 constexpr size_t kCurrentQueueSize{10 * 1024};
37 constexpr size_t kNextQueueSize{10 * 1024};
40 class ObserverManager::CurrentQueue {
42 CurrentQueue() : queue_(kCurrentQueueSize) {
43 if (FLAGS_observer_manager_pool_size < 1) {
44 LOG(ERROR) << "--observer_manager_pool_size should be >= 1";
45 FLAGS_observer_manager_pool_size = 1;
47 for (int32_t i = 0; i < FLAGS_observer_manager_pool_size; ++i) {
48 threads_.emplace_back([&]() {
49 ObserverManager::inManagerThread_ = true;
52 Function<void()> task;
53 queue_.blockingRead(task);
62 LOG(ERROR) << "Exception while running CurrentQueue task: "
63 << exceptionStr(std::current_exception());
71 for (size_t i = 0; i < threads_.size(); ++i) {
72 queue_.blockingWrite(nullptr);
75 for (auto& thread : threads_) {
79 CHECK(queue_.isEmpty());
82 void add(Function<void()> task) {
83 if (ObserverManager::inManagerThread()) {
84 if (!queue_.write(std::move(task))) {
85 throw std::runtime_error("Too many Observers scheduled for update.");
88 queue_.blockingWrite(std::move(task));
93 MPMCQueue<Function<void()>> queue_;
94 std::vector<std::thread> threads_;
97 class ObserverManager::NextQueue {
99 explicit NextQueue(ObserverManager& manager)
100 : manager_(manager), queue_(kNextQueueSize) {
101 thread_ = std::thread([&]() {
105 queue_.blockingRead(queueCore);
111 std::vector<Core::Ptr> cores;
112 cores.emplace_back(std::move(queueCore));
115 SharedMutexReadPriority::WriteHolder wh(manager_.versionMutex_);
117 // We can't pick more tasks from the queue after we bumped the
118 // version, so we have to do this while holding the lock.
119 while (cores.size() < kNextQueueSize && queue_.read(queueCore)) {
123 cores.emplace_back(std::move(queueCore));
129 for (auto& core : cores) {
130 manager_.scheduleRefresh(std::move(core), manager_.version_, true);
136 void add(Core::Ptr core) {
137 queue_.blockingWrite(std::move(core));
141 // Emtpy element signals thread to terminate
142 queue_.blockingWrite(nullptr);
147 ObserverManager& manager_;
148 MPMCQueue<Core::Ptr> queue_;
152 ObserverManager::ObserverManager() {
153 currentQueue_ = make_unique<CurrentQueue>();
154 nextQueue_ = make_unique<NextQueue>(*this);
157 ObserverManager::~ObserverManager() {
158 // Destroy NextQueue, before the rest of this object, since it expects
159 // ObserverManager to be alive.
161 currentQueue_.reset();
164 void ObserverManager::scheduleCurrent(Function<void()> task) {
165 currentQueue_->add(std::move(task));
168 void ObserverManager::scheduleNext(Core::Ptr core) {
169 nextQueue_->add(std::move(core));
172 struct ObserverManager::Singleton {
173 static folly::Singleton<ObserverManager> instance;
174 // MSVC 2015 doesn't let us access ObserverManager's constructor if we
175 // try to use a lambda to initialize instance, so we have to create
176 // an actual function instead.
177 static ObserverManager* createManager() {
178 return new ObserverManager();
182 folly::Singleton<ObserverManager> ObserverManager::Singleton::instance(
185 std::shared_ptr<ObserverManager> ObserverManager::getInstance() {
186 return Singleton::instance.try_get();