workqueue.h

/* Copyright (C) 2006-2016 J.F.Dockes
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 *   02110-1301 USA
 */
#ifndef _WORKQUEUE_H_INCLUDED_
#define _WORKQUEUE_H_INCLUDED_
 
#include <chrono>
#include <thread>
#include <string>
#include <queue>
#include <list>
#include <mutex>
#include <condition_variable>
 
#ifdef MDU_INCLUDE_LOG
#include MDU_INCLUDE_LOG
#else
#include "log.h"
#endif
 
using namespace std::chrono_literals;
 
template <class T> class WorkQueue {
public:
 
    WorkQueue(const std::string& name, size_t hi = 0, size_t lo = 1)
        : m_name(name), m_high(hi), m_low(lo)
    {
    }
 
    ~WorkQueue() {
        if (!m_worker_threads.empty()) {
            setTerminateAndWait();
        }
    }
    WorkQueue(const WorkQueue&) = delete;
    WorkQueue& operator=(const WorkQueue&) = delete;
 
    void setTaskFreeFunc(void (*func)(T&)) {
        m_taskfreefunc = func;
    }
 
    void closeShop() {
        m_openforbusiness = false;
    }
 
    bool start(int nworkers, void *(workproc)(void *), void *arg) {
        std::unique_lock<std::mutex> lock(m_mutex);
        for (int i = 0; i < nworkers; i++) {
            Worker w;
            w.thr = std::thread(workproc, arg);
            m_worker_threads.push_back(std::move(w));
        }
        return true;
    }
 
    bool put(T t, bool flushprevious = false) {
        std::unique_lock<std::mutex> lock(m_mutex);
        if (!ok() || !m_openforbusiness) {
            LOGERR("WorkQueue::put: "  << m_name << ": ok: " << ok() << " openforbusiness " << 
                   m_openforbusiness << "\n");
            return false;
        }
        LOGDEB2("WorkQueue::put: "  << m_name << "\n");
 
        while (ok() && m_high > 0 && m_queue.size() >= m_high) {
            m_clientsleeps++;
            // Keep the order: we test ok() AFTER the sleep...
            m_clients_waiting++;
            m_ccond.wait(lock);
            if (!ok()) {
                m_clients_waiting--;
                return false;
            }
            m_clients_waiting--;
        }
        if (flushprevious) {
            while (!m_queue.empty()) {
                if (m_taskfreefunc) {
                    T& d = m_queue.front();
                    m_taskfreefunc(d);
                }
                m_queue.pop();
            }
        }
 
        m_queue.push(t);
        if (m_workers_waiting > 0) {
            // Just wake one worker, there is only one new task.
            m_wcond.notify_one();
        } else {
            m_nowake++;
        }
 
        return true;
    }
 
    bool waitIdle() {
        std::unique_lock<std::mutex> lock(m_mutex);
        // We're not done while:
        //  - the queue is not empty and we have some workers left
        //  - OR some workers are working (not exited or back waiting for a task).
        while (((m_queue.size() > 0 && m_workers_exited < m_worker_threads.size()) ||
                (m_workers_waiting + m_workers_exited) < m_worker_threads.size())) {
            LOGDEB0("waitIdle: " << m_name << " qsz " << m_queue.size() <<
                    " wwaiting " << m_workers_waiting << " wexit " << m_workers_exited << " nthr " <<
                    m_worker_threads.size() << "\n");
            m_clients_waiting++;
            m_ccond.wait(lock);
            m_clients_waiting--;
        }
 
        return ok();
    }
 
    void *setTerminateAndWait() {
        std::unique_lock<std::mutex> lock(m_mutex);
        LOGDEB("setTerminateAndWait:"  << m_name << "\n");
 
        if (m_worker_threads.empty()) {
            // Already called ?
            return (void*)0;
        }
 
        // Wait for all worker threads to have called workerExit()
        m_ok = false;
        while (m_workers_exited < m_worker_threads.size()) {
            m_wcond.notify_all();
            m_clients_waiting++;
            m_ccond.wait(lock);
            m_clients_waiting--;
        }
 
        LOGDEB(m_name << ": tasks " << m_tottasks << " nowakes " << m_nowake << " wsleeps " <<
               m_workersleeps << " csleeps " << m_clientsleeps << "\n");
        // Perform the thread joins and compute overall status
        // Workers return (void*)1 if ok
        void *statusall = (void*)1;
        while (!m_worker_threads.empty()) {
            void *status = (void*) 1;
            m_worker_threads.front().thr.join();
            if (status == (void *)0) {
                statusall = status;
            }
            m_worker_threads.pop_front();
        }
 
        // Reset to start state.
        m_workers_exited = m_clients_waiting = m_workers_waiting =
            m_tottasks = m_nowake = m_workersleeps = m_clientsleeps = 0;
        m_ok = true;
 
        LOGDEB("setTerminateAndWait:"  << m_name << " done\n");
        return statusall;
    }
 
    bool take(T* tp, size_t *szp = nullptr, std::chrono::duration<double> waitdur = {-1ms}) {
        std::unique_lock<std::mutex> lock(m_mutex);
        if (!ok()) {
            LOGDEB("WorkQueue::take:"  << m_name << ": not ok\n");
            return false;
        }
 
        while (ok() && m_queue.size() < m_low) {
            m_workersleeps++;
            m_workers_waiting++;
            if (m_queue.empty()) {
                m_ccond.notify_all();
            }
            if (waitdur < 0ms) {
                m_wcond.wait(lock);
            } else if (m_wcond.wait_for(lock, waitdur) == std::cv_status::timeout) {
                m_workers_waiting--;
                *tp = nullptr;
                return true;
            }
 
            if (!ok()) {
                // !ok is a normal condition when shutting down
                m_workers_waiting--;
                return false;
            }
            m_workers_waiting--;
        }
 
        m_tottasks++;
        *tp = m_queue.front();
        if (szp) {
            *szp = m_queue.size();
        }
        m_queue.pop();
        if (m_clients_waiting > 0) {
            // No reason to wake up more than one client thread
            m_ccond.notify_one();
        } else {
            m_nowake++;
        }
        return true;
    }
 
    bool waitminsz(size_t sz) {
        std::unique_lock<std::mutex> lock(m_mutex);
        if (!ok()) {
            return false;
        }
 
        while (ok() && m_queue.size() < sz) {
            m_workersleeps++;
            m_workers_waiting++;
            if (m_queue.empty()) {
                m_ccond.notify_all();
            }
            m_wcond.wait(lock);
            if (!ok()) {
                m_workers_waiting--;
                return false;
            }
            m_workers_waiting--;
        }
        return true;
    }
 
    void workerExit() {
        LOGDEB("workerExit:"  << m_name << "\n");
        std::unique_lock<std::mutex> lock(m_mutex);
        m_workers_exited++;
        m_ok = false;
        m_ccond.notify_all();
    }
 
    size_t qsize() {
        std::unique_lock<std::mutex> lock(m_mutex);
        return m_queue.size();
    }
 
private:
    bool ok() {
        bool isok = m_ok && m_workers_exited == 0 && !m_worker_threads.empty();
        if (!isok) {
            LOGDEB("WorkQueue:ok:" << m_name << ": not ok m_ok " << m_ok <<
                   " m_workers_exited " << m_workers_exited <<
                   " m_worker_threads size " << m_worker_threads.size() <<
                   "\n");
        }
        return isok;
    }
 
    struct Worker {
        std::thread         thr;
    };
    
    void (*m_taskfreefunc)(T&){nullptr};
    // Configuration
    std::string m_name;
    size_t m_high;
    size_t m_low;
 
    // Worker threads having called exit. Used to decide when we're done
    unsigned int m_workers_exited{0};
    // Status
    bool m_ok{true};
 
    // Accepting new tasks
    bool m_openforbusiness{true};
    
    // Our threads. 
    std::list<Worker> m_worker_threads;
 
    // Jobs input queue
    std::queue<T> m_queue;
    
    // Synchronization
    std::condition_variable m_ccond;
    std::condition_variable m_wcond;
    std::mutex m_mutex;
 
    // Client/Worker threads currently waiting for a job
    unsigned int m_clients_waiting{0};
    unsigned int m_workers_waiting{0};
 
    // Statistics
    unsigned int m_tottasks{0};
    unsigned int m_nowake{0};
    unsigned int m_workersleeps{0};
    unsigned int m_clientsleeps{0};
};
 
#endif /* _WORKQUEUE_H_INCLUDED_ */