2 * Copyright 2014 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.
17 #include <folly/experimental/Singleton.h>
25 static constexpr std::chrono::seconds kDestroyWaitTime{5};
29 SingletonVault::~SingletonVault() { destroyInstances(); }
31 void SingletonVault::destroyInstances() {
32 RWSpinLock::WriteHolder state_wh(&stateMutex_);
34 if (state_ == SingletonVaultState::Quiescing) {
37 state_ = SingletonVaultState::Quiescing;
39 RWSpinLock::ReadHolder state_rh(std::move(state_wh));
42 RWSpinLock::ReadHolder rh(&mutex_);
44 CHECK_GE(singletons_.size(), creation_order_.size());
46 for (auto type_iter = creation_order_.rbegin();
47 type_iter != creation_order_.rend();
49 destroyInstance(singletons_.find(*type_iter));
54 RWSpinLock::WriteHolder wh(&mutex_);
55 creation_order_.clear();
59 /* Destroy and clean-up one singleton. Must be invoked while holding
60 * a read lock on mutex_.
61 * @param typeDescriptor - the type key for the removed singleton.
63 void SingletonVault::destroyInstance(SingletonMap::iterator entry_it) {
64 const auto& type = entry_it->first;
65 auto& entry = *(entry_it->second);
67 entry.state = detail::SingletonEntryState::Dead;
68 entry.instance.reset();
69 auto wait_result = entry.destroy_baton->timed_wait(
70 std::chrono::steady_clock::now() + kDestroyWaitTime);
72 LOG(ERROR) << "Singleton of type " << type.prettyName() << " has a living "
73 << "reference at destroyInstances time; beware! Raw pointer "
74 << "is " << entry.instance_ptr << ". It is very likely that "
75 << "some other singleton is holding a shared_ptr to it. Make "
76 << "sure dependencies between these singletons are properly "
81 void SingletonVault::reenableInstances() {
82 RWSpinLock::WriteHolder state_wh(&stateMutex_);
84 stateCheck(SingletonVaultState::Quiescing);
86 state_ = SingletonVaultState::Running;
89 void SingletonVault::scheduleDestroyInstances() {
90 RequestContext::getStaticContext();
92 class SingletonVaultDestructor {
94 ~SingletonVaultDestructor() {
95 SingletonVault::singleton()->destroyInstances();
99 // Here we intialize a singleton, which calls destroyInstances in its
100 // destructor. Because of singleton destruction order - it will be destroyed
101 // before all the singletons, which were initialized before it and after all
102 // the singletons initialized after it.
103 static SingletonVaultDestructor singletonVaultDestructor;