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/FixedString.h>
20 #include <folly/Format.h>
21 #include <folly/MPMCQueue.h>
22 #include <folly/Singleton.h>
23 #include <folly/ThreadName.h>
24 #include <folly/portability/GFlags.h>
27 namespace observer_detail {
29 FOLLY_TLS bool ObserverManager::inManagerThread_{false};
30 FOLLY_TLS ObserverManager::DependencyRecorder::Dependencies*
31 ObserverManager::DependencyRecorder::currentDependencies_{nullptr};
34 observer_manager_pool_size,
36 "How many internal threads ObserverManager should use");
38 static constexpr auto kObserverManagerThreadNamePrefix =
39 folly::makeFixedString("ObserverMngr");
42 constexpr size_t kCurrentQueueSize{10 * 1024};
43 constexpr size_t kNextQueueSize{10 * 1024};
46 class ObserverManager::CurrentQueue {
48 CurrentQueue() : queue_(kCurrentQueueSize) {
49 if (FLAGS_observer_manager_pool_size < 1) {
50 LOG(ERROR) << "--observer_manager_pool_size should be >= 1";
51 FLAGS_observer_manager_pool_size = 1;
53 for (int32_t i = 0; i < FLAGS_observer_manager_pool_size; ++i) {
54 threads_.emplace_back([this, i]() {
56 folly::sformat("{}{}", kObserverManagerThreadNamePrefix, i));
57 ObserverManager::inManagerThread_ = true;
60 Function<void()> task;
61 queue_.blockingRead(task);
70 LOG(ERROR) << "Exception while running CurrentQueue task: "
71 << exceptionStr(std::current_exception());
79 for (size_t i = 0; i < threads_.size(); ++i) {
80 queue_.blockingWrite(nullptr);
83 for (auto& thread : threads_) {
87 CHECK(queue_.isEmpty());
90 void add(Function<void()> task) {
91 if (ObserverManager::inManagerThread()) {
92 if (!queue_.write(std::move(task))) {
93 throw std::runtime_error("Too many Observers scheduled for update.");
96 queue_.blockingWrite(std::move(task));
101 MPMCQueue<Function<void()>> queue_;
102 std::vector<std::thread> threads_;
105 class ObserverManager::NextQueue {
107 explicit NextQueue(ObserverManager& manager)
108 : manager_(manager), queue_(kNextQueueSize) {
109 thread_ = std::thread([&]() {
113 queue_.blockingRead(queueCore);
119 std::vector<Core::Ptr> cores;
120 cores.emplace_back(std::move(queueCore));
123 SharedMutexReadPriority::WriteHolder wh(manager_.versionMutex_);
125 // We can't pick more tasks from the queue after we bumped the
126 // version, so we have to do this while holding the lock.
127 while (cores.size() < kNextQueueSize && queue_.read(queueCore)) {
131 cores.emplace_back(std::move(queueCore));
137 for (auto& core : cores) {
138 manager_.scheduleRefresh(std::move(core), manager_.version_, true);
144 void add(Core::Ptr core) {
145 queue_.blockingWrite(std::move(core));
149 // Emtpy element signals thread to terminate
150 queue_.blockingWrite(nullptr);
155 ObserverManager& manager_;
156 MPMCQueue<Core::Ptr> queue_;
160 ObserverManager::ObserverManager() {
161 currentQueue_ = make_unique<CurrentQueue>();
162 nextQueue_ = make_unique<NextQueue>(*this);
165 ObserverManager::~ObserverManager() {
166 // Destroy NextQueue, before the rest of this object, since it expects
167 // ObserverManager to be alive.
169 currentQueue_.reset();
172 void ObserverManager::scheduleCurrent(Function<void()> task) {
173 currentQueue_->add(std::move(task));
176 void ObserverManager::scheduleNext(Core::Ptr core) {
177 nextQueue_->add(std::move(core));
180 struct ObserverManager::Singleton {
181 static folly::Singleton<ObserverManager> instance;
182 // MSVC 2015 doesn't let us access ObserverManager's constructor if we
183 // try to use a lambda to initialize instance, so we have to create
184 // an actual function instead.
185 static ObserverManager* createManager() {
186 return new ObserverManager();
190 folly::Singleton<ObserverManager> ObserverManager::Singleton::instance(
193 std::shared_ptr<ObserverManager> ObserverManager::getInstance() {
194 return Singleton::instance.try_get();