C++ unique_lock::lock方法代码示例

static NOINLINE_DECL stdx::cv_status cvWaitUntilWithClockSource(ClockSource* clockSource,
                                                                stdx::condition_variable& cv,
                                                                stdx::unique_lock<stdx::mutex>& m,
                                                                Date_t deadline) {
    if (deadline <= clockSource->now()) {
        return stdx::cv_status::timeout;
    }

    struct AlarmInfo {
        stdx::mutex controlMutex;
        stdx::mutex* waitMutex;
        stdx::condition_variable* waitCV;
        stdx::cv_status cvWaitResult = stdx::cv_status::no_timeout;
    };
    auto alarmInfo = std::make_shared<AlarmInfo>();
    alarmInfo->waitCV = &cv;
    alarmInfo->waitMutex = m.mutex();
    invariantOK(clockSource->setAlarm(deadline, [alarmInfo] {
        stdx::lock_guard<stdx::mutex> controlLk(alarmInfo->controlMutex);
        alarmInfo->cvWaitResult = stdx::cv_status::timeout;
        if (!alarmInfo->waitMutex) {
            return;
        }
        stdx::lock_guard<stdx::mutex> waitLk(*alarmInfo->waitMutex);
        alarmInfo->waitCV->notify_all();
    }));
    cv.wait(m);
    m.unlock();
    stdx::lock_guard<stdx::mutex> controlLk(alarmInfo->controlMutex);
    m.lock();
    alarmInfo->waitMutex = nullptr;
    alarmInfo->waitCV = nullptr;
    return alarmInfo->cvWaitResult;
}

// fulfills as many outstanding requests as possible
void ConnectionPool::SpecificPool::fulfillRequests(stdx::unique_lock<stdx::mutex>& lk) {
    // If some other thread (possibly this thread) is fulfilling requests,
    // don't keep padding the callstack.
    if (_inFulfillRequests)
        return;

    _inFulfillRequests = true;
    auto guard = MakeGuard([&] { _inFulfillRequests = false; });

    while (_requests.size()) {
        // _readyPool is an LRUCache, so its begin() object is the MRU item.
        auto iter = _readyPool.begin();

        if (iter == _readyPool.end())
            break;

        // Grab the connection and cancel its timeout
        auto conn = std::move(iter->second);
        _readyPool.erase(iter);
        conn->cancelTimeout();

        if (!conn->isHealthy()) {
            log() << "dropping unhealthy pooled connection to " << conn->getHostAndPort();

            if (_readyPool.empty()) {
                log() << "after drop, pool was empty, going to spawn some connections";
                // Spawn some more connections to the bad host if we're all out.
                spawnConnections(lk);
            }

            // Drop the bad connection.
            conn.reset();
            // Retry.
            continue;
        }

        // Grab the request and callback
        auto cb = std::move(_requests.top().second);
        _requests.pop();

        auto connPtr = conn.get();

        // check out the connection
        _checkedOutPool[connPtr] = std::move(conn);

        updateStateInLock();

        // pass it to the user
        connPtr->resetToUnknown();
        lk.unlock();
        cb(ConnectionHandle(connPtr, ConnectionHandleDeleter(_parent)));
        lk.lock();
    }
}

/**
 * Consumes available tasks.
 *
 * We distinguish between calls to consume on the networking thread and off of
 * it. For off thread calls, we try to initiate a consume via setAlarm, while on
 * it we invoke directly. This allows us to use the network interface's threads
 * as our own pool, which should reduce context switches if our tasks are
 * getting scheduled by network interface tasks.
 */
void NetworkInterfaceThreadPool::consumeTasks(stdx::unique_lock<stdx::mutex> lk) {
    if (_consumingTasks || _tasks.empty())
        return;

    if (!(_inShutdown || _net->onNetworkThread())) {
        if (!_registeredAlarm) {
            _registeredAlarm = true;
            lk.unlock();
            _net->setAlarm(_net->now(),
                           [this] {
                               stdx::unique_lock<stdx::mutex> lk(_mutex);
                               _registeredAlarm = false;
                               consumeTasks(std::move(lk));
                           });
        }

        return;
    }

    _consumingTasks = true;
    const auto consumingTasksGuard = MakeGuard([&] { _consumingTasks = false; });

    decltype(_tasks) tasks;

    while (_tasks.size()) {
        using std::swap;
        swap(tasks, _tasks);

        lk.unlock();
        const auto lkGuard = MakeGuard([&] { lk.lock(); });

        for (auto&& task : tasks) {
            try {
                task();
            } catch (...) {
                severe() << "Exception escaped task in network interface thread pool";
                std::terminate();
            }
        }

        tasks.clear();
    }

    if (_joining)
        _joiningCondition.notify_one();
}

// spawn enough connections to satisfy open requests and minpool, while
// honoring maxpool
void ConnectionPool::SpecificPool::spawnConnections(stdx::unique_lock<stdx::mutex>& lk,
                                                    const HostAndPort& hostAndPort) {
    // We want minConnections <= outstanding requests <= maxConnections
    auto target = [&] {
        return std::max(
            _parent->_options.minConnections,
            std::min(_requests.size() + _checkedOutPool.size(), _parent->_options.maxConnections));
    };

    // While all of our inflight connections are less than our target
    while (_readyPool.size() + _processingPool.size() + _checkedOutPool.size() < target()) {
        // make a new connection and put it in processing
        auto handle = _parent->_factory->makeConnection(hostAndPort, _generation);
        auto connPtr = handle.get();
        _processingPool[connPtr] = std::move(handle);

        ++_created;

        // Run the setup callback
        lk.unlock();
        connPtr->setup(_parent->_options.refreshTimeout,
                       [this](ConnectionInterface* connPtr, Status status) {
                           connPtr->indicateUsed();

                           stdx::unique_lock<stdx::mutex> lk(_parent->_mutex);

                           auto conn = takeFromProcessingPool(connPtr);

                           if (conn->getGeneration() != _generation) {
                               // If the host and port was dropped, let the
                               // connection lapse
                           } else if (status.isOK()) {
                               addToReady(lk, std::move(conn));
                           } else {
                               // If the setup failed, cascade the failure edge
                               processFailure(status, std::move(lk));
                           }
                       });
        // Note that this assumes that the refreshTimeout is sound for the
        // setupTimeout

        lk.lock();
    }
}

// fulfills as many outstanding requests as possible
void ConnectionPool::SpecificPool::fulfillRequests(stdx::unique_lock<stdx::mutex>& lk) {
    // If some other thread (possibly this thread) is fulfilling requests,
    // don't keep padding the callstack.
    if (_inFulfillRequests)
        return;

    _inFulfillRequests = true;
    auto guard = MakeGuard([&] { _inFulfillRequests = false; });

    while (_requests.size()) {
        auto iter = _readyPool.begin();

        if (iter == _readyPool.end())
            break;

        // Grab the connection and cancel its timeout
        auto conn = std::move(iter->second);
        _readyPool.erase(iter);
        conn->cancelTimeout();

        // Grab the request and callback
        auto cb = std::move(_requests.top().second);
        _requests.pop();

        auto connPtr = conn.get();

        // check out the connection
        _checkedOutPool[connPtr] = std::move(conn);

        updateStateInLock();

        // pass it to the user
        lk.unlock();
        cb(ConnectionHandle(connPtr, ConnectionHandleDeleter(_parent)));
        lk.lock();
    }
}

// spawn enough connections to satisfy open requests and minpool, while
// honoring maxpool
void ConnectionPool::SpecificPool::spawnConnections(stdx::unique_lock<stdx::mutex>& lk) {
    // If some other thread (possibly this thread) is spawning connections,
    // don't keep padding the callstack.
    if (_inSpawnConnections)
        return;

    _inSpawnConnections = true;
    auto guard = MakeGuard([&] { _inSpawnConnections = false; });

    // We want minConnections <= outstanding requests <= maxConnections
    auto target = [&] {
        return std::max(
            _parent->_options.minConnections,
            std::min(_requests.size() + _checkedOutPool.size(), _parent->_options.maxConnections));
    };

    // While all of our inflight connections are less than our target
    while (_readyPool.size() + _processingPool.size() + _checkedOutPool.size() < target()) {
        std::unique_ptr<ConnectionPool::ConnectionInterface> handle;
        try {
            // make a new connection and put it in processing
            handle = _parent->_factory->makeConnection(_hostAndPort, _generation);
        } catch (std::system_error& e) {
            severe() << "Failed to construct a new connection object: " << e.what();
            fassertFailed(40336);
        }

        auto connPtr = handle.get();
        _processingPool[connPtr] = std::move(handle);

        ++_created;

        // Run the setup callback
        lk.unlock();
        connPtr->setup(
            _parent->_options.refreshTimeout, [this](ConnectionInterface* connPtr, Status status) {
                connPtr->indicateUsed();

                stdx::unique_lock<stdx::mutex> lk(_parent->_mutex);

                auto conn = takeFromProcessingPool(connPtr);

                if (conn->getGeneration() != _generation) {
                    // If the host and port was dropped, let the
                    // connection lapse
                } else if (status.isOK()) {
                    addToReady(lk, std::move(conn));
                } else if (status.code() == ErrorCodes::NetworkInterfaceExceededTimeLimit) {
                    // If we've exceeded the time limit, restart the connect, rather than
                    // failing all operations.  We do this because the various callers
                    // have their own time limit which is unrelated to our internal one.
                    spawnConnections(lk);
                } else {
                    // If the setup failed, cascade the failure edge
                    processFailure(status, std::move(lk));
                }
            });
        // Note that this assumes that the refreshTimeout is sound for the
        // setupTimeout

        lk.lock();
    }
}

void ConnectionPool::SpecificPool::returnConnection(ConnectionInterface* connPtr,
                                                    stdx::unique_lock<stdx::mutex> lk) {
    auto needsRefreshTP = connPtr->getLastUsed() + _parent->_options.refreshRequirement;

    auto conn = takeFromPool(_checkedOutPool, connPtr);

    updateStateInLock();

    // Users are required to call indicateSuccess() or indicateFailure() before allowing
    // a connection to be returned. Otherwise, we have entered an unknown state.
    invariant(conn->getStatus() != kConnectionStateUnknown);

    if (conn->getGeneration() != _generation) {
        // If the connection is from an older generation, just return.
        return;
    }

    if (!conn->getStatus().isOK()) {
        // TODO: alert via some callback if the host is bad
        log() << "Ending connection to host " << _hostAndPort << " due to bad connection status; "
              << openConnections(lk) << " connections to that host remain open";
        return;
    }

    auto now = _parent->_factory->now();
    if (needsRefreshTP <= now) {
        // If we need to refresh this connection

        if (_readyPool.size() + _processingPool.size() + _checkedOutPool.size() >=
            _parent->_options.minConnections) {
            // If we already have minConnections, just let the connection lapse
            log() << "Ending idle connection to host " << _hostAndPort
                  << " because the pool meets constraints; " << openConnections(lk)
                  << " connections to that host remain open";
            return;
        }

        _processingPool[connPtr] = std::move(conn);

        // Unlock in case refresh can occur immediately
        lk.unlock();
        connPtr->refresh(_parent->_options.refreshTimeout,
                         [this](ConnectionInterface* connPtr, Status status) {
                             connPtr->indicateUsed();

                             stdx::unique_lock<stdx::mutex> lk(_parent->_mutex);

                             auto conn = takeFromProcessingPool(connPtr);

                             // If the host and port were dropped, let this lapse
                             if (conn->getGeneration() != _generation)
                                 return;

                             // If we're in shutdown, we don't need refreshed connections
                             if (_state == State::kInShutdown)
                                 return;

                             // If the connection refreshed successfully, throw it back in the ready
                             // pool
                             if (status.isOK()) {
                                 addToReady(lk, std::move(conn));
                                 return;
                             }

                             // If we've exceeded the time limit, start a new connect, rather than
                             // failing all operations.  We do this because the various callers have
                             // their own time limit which is unrelated to our internal one.
                             if (status.code() == ErrorCodes::NetworkInterfaceExceededTimeLimit) {
                                 log() << "Pending connection to host " << _hostAndPort
                                       << " did not complete within the connection timeout,"
                                       << " retrying with a new connection;" << openConnections(lk)
                                       << " connections to that host remain open";
                                 spawnConnections(lk);
                                 return;
                             }

                             // Otherwise pass the failure on through
                             processFailure(status, std::move(lk));
                         });
        lk.lock();
    } else {
        // If it's fine as it is, just put it in the ready queue
        addToReady(lk, std::move(conn));
    }

    updateStateInLock();
}

void ConnectionPool::SpecificPool::returnConnection(ConnectionInterface* connPtr,
                                                    stdx::unique_lock<stdx::mutex> lk) {
    auto needsRefreshTP = connPtr->getLastUsed() + _parent->_options.refreshRequirement;

    auto conn = takeFromPool(_checkedOutPool, connPtr);

    updateStateInLock();

    // Users are required to call indicateSuccess() or indicateFailure() before allowing
    // a connection to be returned. Otherwise, we have entered an unknown state.
    invariant(conn->getStatus() != kConnectionStateUnknown);

    if (conn->getGeneration() != _generation) {
        // If the connection is from an older generation, just return.
        return;
    }

    if (!conn->getStatus().isOK()) {
        // TODO: alert via some callback if the host is bad
        return;
    }

    auto now = _parent->_factory->now();
    if (needsRefreshTP <= now) {
        // If we need to refresh this connection

        if (_readyPool.size() + _processingPool.size() + _checkedOutPool.size() >=
            _parent->_options.minConnections) {
            // If we already have minConnections, just let the connection lapse
            return;
        }

        _processingPool[connPtr] = std::move(conn);

        // Unlock in case refresh can occur immediately
        lk.unlock();
        connPtr->refresh(_parent->_options.refreshTimeout,
                         [this](ConnectionInterface* connPtr, Status status) {
                             connPtr->indicateUsed();

                             stdx::unique_lock<stdx::mutex> lk(_parent->_mutex);

                             auto conn = takeFromProcessingPool(connPtr);

                             // If the host and port were dropped, let this lapse
                             if (conn->getGeneration() != _generation)
                                 return;

                             // If we're in shutdown, we don't need refreshed connections
                             if (_state == State::kInShutdown)
                                 return;

                             // If the connection refreshed successfully, throw it back in the ready
                             // pool
                             if (status.isOK()) {
                                 addToReady(lk, std::move(conn));
                                 return;
                             }

                             // Otherwise pass the failure on through
                             processFailure(status, std::move(lk));
                         });
        lk.lock();
    } else {
        // If it's fine as it is, just put it in the ready queue
        addToReady(lk, std::move(conn));
    }

    updateStateInLock();
}