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>
20 #include <folly/portability/GFlags.h>
23 namespace observer_detail {
25 FOLLY_TLS bool ObserverManager::inManagerThread_{false};
26 FOLLY_TLS ObserverManager::DependencyRecorder::Dependencies*
27 ObserverManager::DependencyRecorder::currentDependencies_{nullptr};
30 observer_manager_pool_size,
32 "How many internal threads ObserverManager should use");
35 constexpr size_t kCurrentQueueSize{10 * 1024};
36 constexpr size_t kNextQueueSize{10 * 1024};
39 class ObserverManager::CurrentQueue {
41 CurrentQueue() : queue_(kCurrentQueueSize) {
42 if (FLAGS_observer_manager_pool_size < 1) {
43 LOG(ERROR) << "--observer_manager_pool_size should be >= 1";
44 FLAGS_observer_manager_pool_size = 1;
46 for (int32_t i = 0; i < FLAGS_observer_manager_pool_size; ++i) {
47 threads_.emplace_back([&]() {
48 ObserverManager::inManagerThread_ = true;
51 Function<void()> task;
52 queue_.blockingRead(task);
61 LOG(ERROR) << "Exception while running CurrentQueue task: "
62 << exceptionStr(std::current_exception());
70 for (size_t i = 0; i < threads_.size(); ++i) {
71 queue_.blockingWrite(nullptr);
74 for (auto& thread : threads_) {
78 CHECK(queue_.isEmpty());
81 void add(Function<void()> task) {
82 if (ObserverManager::inManagerThread()) {
83 if (!queue_.write(std::move(task))) {
84 throw std::runtime_error("Too many Observers scheduled for update.");
87 queue_.blockingWrite(std::move(task));
92 MPMCQueue<Function<void()>> queue_;
93 std::vector<std::thread> threads_;
96 class ObserverManager::NextQueue {
98 explicit NextQueue(ObserverManager& manager)
99 : manager_(manager), queue_(kNextQueueSize) {
100 thread_ = std::thread([&]() {
104 queue_.blockingRead(queueCore);
110 std::vector<Core::Ptr> cores;
111 cores.emplace_back(std::move(queueCore));
114 SharedMutexReadPriority::WriteHolder wh(manager_.versionMutex_);
116 // We can't pick more tasks from the queue after we bumped the
117 // version, so we have to do this while holding the lock.
118 while (cores.size() < kNextQueueSize && queue_.read(queueCore)) {
122 cores.emplace_back(std::move(queueCore));
128 for (auto& core : cores) {
129 manager_.scheduleRefresh(std::move(core), manager_.version_, true);
135 void add(Core::Ptr core) {
136 queue_.blockingWrite(std::move(core));
140 // Emtpy element signals thread to terminate
141 queue_.blockingWrite(nullptr);
146 ObserverManager& manager_;
147 MPMCQueue<Core::Ptr> queue_;
151 ObserverManager::ObserverManager() {
152 currentQueue_ = make_unique<CurrentQueue>();
153 nextQueue_ = make_unique<NextQueue>(*this);
156 ObserverManager::~ObserverManager() {
157 // Destroy NextQueue, before the rest of this object, since it expects
158 // ObserverManager to be alive.
160 currentQueue_.reset();
163 void ObserverManager::scheduleCurrent(Function<void()> task) {
164 currentQueue_->add(std::move(task));
167 void ObserverManager::scheduleNext(Core::Ptr core) {
168 nextQueue_->add(std::move(core));
171 struct ObserverManager::Singleton {
172 static folly::Singleton<ObserverManager> instance;
173 // MSVC 2015 doesn't let us access ObserverManager's constructor if we
174 // try to use a lambda to initialize instance, so we have to create
175 // an actual function instead.
176 static ObserverManager* createManager() {
177 return new ObserverManager();
181 folly::Singleton<ObserverManager> ObserverManager::Singleton::instance(
184 std::shared_ptr<ObserverManager> ObserverManager::getInstance() {
185 return Singleton::instance.try_get();