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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kExecutor
#include "mongo/platform/basic.h"
#include "mongo/transport/service_executor_synchronous.h"
#include "mongo/logv2/log.h"
#include "mongo/stdx/thread.h"
#include "mongo/transport/service_entry_point_utils.h"
#include "mongo/transport/service_executor_gen.h"
#include "mongo/util/processinfo.h"
namespace mongo {
namespace transport {
namespace {
constexpr auto kThreadsRunning = "threadsRunning"_sd;
constexpr auto kExecutorLabel = "executor"_sd;
constexpr auto kExecutorName = "passthrough"_sd;
} // namespace
thread_local std::deque<ServiceExecutor::Task> ServiceExecutorSynchronous::_localWorkQueue = {};
thread_local int ServiceExecutorSynchronous::_localRecursionDepth = 0;
thread_local int64_t ServiceExecutorSynchronous::_localThreadIdleCounter = 0;
ServiceExecutorSynchronous::ServiceExecutorSynchronous(ServiceContext* ctx)
: _shutdownCondition(std::make_shared<stdx::condition_variable>()) {}
Status ServiceExecutorSynchronous::start() {
_numHardwareCores = static_cast<size_t>(ProcessInfo::getNumAvailableCores());
_stillRunning.store(true);
return Status::OK();
}
Status ServiceExecutorSynchronous::shutdown(Milliseconds timeout) {
LOGV2_DEBUG(22982, 3, "Shutting down passthrough executor");
_stillRunning.store(false);
stdx::unique_lock<Latch> lock(_shutdownMutex);
bool result = _shutdownCondition->wait_for(lock, timeout.toSystemDuration(), [this]() {
return _numRunningWorkerThreads.load() == 0;
});
return result
? Status::OK()
: Status(ErrorCodes::Error::ExceededTimeLimit,
"passthrough executor couldn't shutdown all worker threads within time limit.");
}
Status ServiceExecutorSynchronous::schedule(Task task, ScheduleFlags flags) {
if (!_stillRunning.load()) {
return Status{ErrorCodes::ShutdownInProgress, "Executor is not running"};
}
if (!_localWorkQueue.empty()) {
/*
* In perf testing we found that yielding after running a each request produced
* at 5% performance boost in microbenchmarks if the number of worker threads
* was greater than the number of available cores.
*/
if (flags & ScheduleFlags::kMayYieldBeforeSchedule) {
if (_numRunningWorkerThreads.loadRelaxed() > _numHardwareCores) {
stdx::this_thread::yield();
}
}
// Execute task directly (recurse) if allowed by the caller as it produced better
// performance in testing. Try to limit the amount of recursion so we don't blow up the
// stack, even though this shouldn't happen with this executor that uses blocking network
// I/O.
if ((flags & ScheduleFlags::kMayRecurse) &&
(_localRecursionDepth < synchronousServiceExecutorRecursionLimit.loadRelaxed())) {
++_localRecursionDepth;
task();
} else {
_localWorkQueue.emplace_back(std::move(task));
}
return Status::OK();
}
// First call to schedule() for this connection, spawn a worker thread that will push jobs
// into the thread local job queue.
LOGV2_DEBUG(22983, 3, "Starting new executor thread in passthrough mode");
Status status = launchServiceWorkerThread(
[this, condVarAnchor = _shutdownCondition, task = std::move(task)]() mutable {
_numRunningWorkerThreads.addAndFetch(1);
_localWorkQueue.emplace_back(std::move(task));
while (!_localWorkQueue.empty() && _stillRunning.loadRelaxed()) {
_localRecursionDepth = 1;
_localWorkQueue.front()();
_localWorkQueue.pop_front();
}
// We maintain an anchor to "_shutdownCondition" to ensure it remains alive even if the
// service executor is freed. Any access to the service executor (through "this") is
// prohibited (and unsafe) after the following line. For more context, see SERVER-49432.
auto numWorkerThreadsStillRunning = _numRunningWorkerThreads.subtractAndFetch(1);
if (numWorkerThreadsStillRunning == 0) {
condVarAnchor->notify_all();
}
});
return status;
}
void ServiceExecutorSynchronous::appendStats(BSONObjBuilder* bob) const {
*bob << kExecutorLabel << kExecutorName << kThreadsRunning
<< static_cast<int>(_numRunningWorkerThreads.loadRelaxed());
}
} // namespace transport
} // namespace mongo
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