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arangodb/arangod/Dispatcher/DispatcherQueue.h

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C++

////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
/// http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Dr. Frank Celler
/// @author Martin Schoenert
////////////////////////////////////////////////////////////////////////////////
#ifndef ARANGOD_DISPATCHER_DISPATCHER_QUEUE_H
#define ARANGOD_DISPATCHER_DISPATCHER_QUEUE_H 1
#include "Basics/Common.h"
#include <boost/lockfree/queue.hpp>
#include "Basics/ConditionVariable.h"
#include "Basics/Mutex.h"
#include "Dispatcher/Dispatcher.h"
namespace arangodb {
namespace rest {
class DispatcherThread;
class Job;
////////////////////////////////////////////////////////////////////////////////
/// @brief dispatcher queue
////////////////////////////////////////////////////////////////////////////////
class DispatcherQueue {
DispatcherQueue(DispatcherQueue const&) = delete;
DispatcherQueue& operator=(DispatcherQueue const&) = delete;
friend class Dispatcher;
friend class DispatcherThread;
public:
//////////////////////////////////////////////////////////////////////////////
/// @brief constructs a new dispatcher queue
//////////////////////////////////////////////////////////////////////////////
DispatcherQueue(Scheduler*, Dispatcher*, size_t id,
Dispatcher::newDispatcherThread_fptr, size_t nrThreads,
size_t nrExtra, size_t maxSize);
~DispatcherQueue();
public:
//////////////////////////////////////////////////////////////////////////////
/// @brief adds a job
//////////////////////////////////////////////////////////////////////////////
int addJob(std::unique_ptr<Job>&, bool startThread);
//////////////////////////////////////////////////////////////////////////////
/// @brief removes a job
//////////////////////////////////////////////////////////////////////////////
void removeJob(Job*);
//////////////////////////////////////////////////////////////////////////////
/// @brief cancels a job
///
/// This will call the method `cancel` of the job. It will not remove the
/// the job from the queue.
//////////////////////////////////////////////////////////////////////////////
bool cancelJob(uint64_t);
//////////////////////////////////////////////////////////////////////////////
/// @brief indicates that thread is doing a blocking operation
//////////////////////////////////////////////////////////////////////////////
void blockThread();
//////////////////////////////////////////////////////////////////////////////
/// @brief indicates that thread has resumed work
//////////////////////////////////////////////////////////////////////////////
void unblockThread();
//////////////////////////////////////////////////////////////////////////////
/// @brief begins the shutdown sequence the queue
//////////////////////////////////////////////////////////////////////////////
void beginShutdown();
//////////////////////////////////////////////////////////////////////////////
/// @brief shuts down the queue
//////////////////////////////////////////////////////////////////////////////
void shutdown();
//////////////////////////////////////////////////////////////////////////////
/// @brief starts a new queue thread
//////////////////////////////////////////////////////////////////////////////
void startQueueThread(bool force);
//////////////////////////////////////////////////////////////////////////////
/// @brief called when a thread has stopped
//////////////////////////////////////////////////////////////////////////////
void removeStartedThread(DispatcherThread* thread);
//////////////////////////////////////////////////////////////////////////////
/// @brief checks if we have too many threads
//////////////////////////////////////////////////////////////////////////////
bool tooManyThreads();
//////////////////////////////////////////////////////////////////////////////
/// @brief checks if we have enough threads
//////////////////////////////////////////////////////////////////////////////
bool notEnoughThreads();
//////////////////////////////////////////////////////////////////////////////
/// @brief sets the process affinity
//////////////////////////////////////////////////////////////////////////////
void setProcessorAffinity(std::vector<size_t> const& cores);
private:
//////////////////////////////////////////////////////////////////////////////
/// @brief deletes old threads
//////////////////////////////////////////////////////////////////////////////
void deleteOldThreads();
private:
//////////////////////////////////////////////////////////////////////////////
/// @brief id
//////////////////////////////////////////////////////////////////////////////
size_t const _id;
//////////////////////////////////////////////////////////////////////////////
/// @brief total number of threads
///
/// This number is fixed. It is the number of pre-configured threads from the
/// configuration file and is the average number of threads running under
/// normal condition. Note that at server start not all threads will be
/// started instantly, as threads will be created on demand.
//////////////////////////////////////////////////////////////////////////////
size_t const _nrThreads;
//////////////////////////////////////////////////////////////////////////////
/// @brief total number of extra/overhead threads
///
/// This number is fixed. It is the maximum number of extra threads that can
/// be created if _nrThreads threads have already been created
//////////////////////////////////////////////////////////////////////////////
size_t const _nrExtra;
//////////////////////////////////////////////////////////////////////////////
/// @brief maximum queue size (number of jobs)
//////////////////////////////////////////////////////////////////////////////
size_t const _maxSize;
//////////////////////////////////////////////////////////////////////////////
/// @brief waker for sleeping threads
//////////////////////////////////////////////////////////////////////////////
basics::ConditionVariable _waitLock;
//////////////////////////////////////////////////////////////////////////////
/// @brief list of ready jobs
//////////////////////////////////////////////////////////////////////////////
boost::lockfree::queue<Job*> _readyJobs;
//////////////////////////////////////////////////////////////////////////////
/// @brief statistics
///
/// This is for statistics only. Never use this number for decisions.
//////////////////////////////////////////////////////////////////////////////
std::atomic<int> _numberJobs;
//////////////////////////////////////////////////////////////////////////////
/// @brief guard for hazard pointer
//////////////////////////////////////////////////////////////////////////////
Mutex _hazardLock;
//////////////////////////////////////////////////////////////////////////////
/// @brief hazard pointer for jobs
//////////////////////////////////////////////////////////////////////////////
std::atomic<Job*> _hazardPointer;
//////////////////////////////////////////////////////////////////////////////
/// @brief queue is shutting down
//////////////////////////////////////////////////////////////////////////////
std::atomic<bool> _stopping;
//////////////////////////////////////////////////////////////////////////////
/// @brief guard for _startedThreads
//////////////////////////////////////////////////////////////////////////////
Mutex _threadsLock;
//////////////////////////////////////////////////////////////////////////////
/// @brief list of started threads
//////////////////////////////////////////////////////////////////////////////
std::set<DispatcherThread*> _startedThreads;
//////////////////////////////////////////////////////////////////////////////
/// @brief list of stopped threads
//////////////////////////////////////////////////////////////////////////////
boost::lockfree::queue<DispatcherThread*> _stoppedThreads;
//////////////////////////////////////////////////////////////////////////////
/// @brief number of running jobs
///
/// As soon as a thread enters its main event loop, this number is increased
/// by
/// one. As soon as the thread leaves its main event loop, this number is
/// decreaes by 1.
///
/// Note that we ignore race conditions, the worst that can happen is that we
/// start one thread too many or shutdown a thread too early. This variable is
/// accessed using "memory_order_seq_cst".
//////////////////////////////////////////////////////////////////////////////
std::atomic<ssize_t> _nrRunning;
//////////////////////////////////////////////////////////////////////////////
/// @brief number of waiting jobs
///
/// Whenever a threads waits for more work, this number is increased by 1. As
/// soon as the thread leaves the wait because it received a signal, this
/// number is decreased by 1.
///
/// This variable is accessed using "memory_order_seq_cst".
//////////////////////////////////////////////////////////////////////////////
std::atomic<ssize_t> _nrWaiting;
//////////////////////////////////////////////////////////////////////////////
/// @brief number of blocked threads
///
/// The number of threads, that are blocked for some reason.
///
/// Note that we ignore race conditions, the worst that can happen is that we
/// start one thread too many or shutdown a thread too early. This variable is
/// accessed using "memory_order_seq_cst".
//////////////////////////////////////////////////////////////////////////////
std::atomic<ssize_t> _nrBlocked;
//////////////////////////////////////////////////////////////////////////////
/// @brief last time we created or deleted a queue thread
///
/// Note that we ignore race conditions, the worst that can happen is that we
/// start one thread too many or shutdown a thread too early. This variable is
/// accessed using "memory_order_seq_cst".
//////////////////////////////////////////////////////////////////////////////
std::atomic<double> _lastChanged;
//////////////////////////////////////////////////////////////////////////////
/// @brief grace period before shuting down queue threads
//////////////////////////////////////////////////////////////////////////////
double const _gracePeriod;
//////////////////////////////////////////////////////////////////////////////
/// @brief scheduler
//////////////////////////////////////////////////////////////////////////////
Scheduler* const _scheduler;
//////////////////////////////////////////////////////////////////////////////
/// @brief dispatcher
//////////////////////////////////////////////////////////////////////////////
Dispatcher* const _dispatcher;
//////////////////////////////////////////////////////////////////////////////
/// @brief thread creator function
//////////////////////////////////////////////////////////////////////////////
Dispatcher::newDispatcherThread_fptr createDispatcherThread;
//////////////////////////////////////////////////////////////////////////////
/// @brief cores to use for affinity
//////////////////////////////////////////////////////////////////////////////
std::vector<size_t> _affinityCores;
//////////////////////////////////////////////////////////////////////////////
/// @brief next affinity core to use
//////////////////////////////////////////////////////////////////////////////
size_t _affinityPos;
//////////////////////////////////////////////////////////////////////////////
/// @brief list of jobs
///
/// There are at most _maxSize jobs.
//////////////////////////////////////////////////////////////////////////////
std::atomic<Job*>* _jobs;
//////////////////////////////////////////////////////////////////////////////
/// @brief list of free job positions
///
/// There are at most _maxSize jobs. But _maxSize is only known at runtime.
//////////////////////////////////////////////////////////////////////////////
boost::lockfree::queue<size_t> _jobPositions;
};
}
}
#endif