bgfetcher.hh

/* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#ifndef BGFETCHER_HH
#define BGFETCHER 1

#include <map>
#include <vector>
#include <list>

#include "common.hh"
#include "dispatcher.hh"

// Forward declaration.
class EventuallyPersistentStore;
class BgFetcher;

/**
 * A DispatcherCallback for BgFetcher
 */
class BgFetcherCallback : public DispatcherCallback {
public:
    BgFetcherCallback(BgFetcher *b) : bgfetcher(b) { }

    bool callback(Dispatcher &d, TaskId t);
    std::string description() {
        return std::string("Batching background fetch.");
    }

private:
    BgFetcher *bgfetcher;
};

/**
 * Dispatcher job responsible for batching data reads and push to
 * underlying storage
 */
class BgFetcher {
public:
    static const double sleepInterval;
    /**
     * Construct a BgFetcher task.
     *
     * @param s the store
     * @param d the dispatcher
     */
    BgFetcher(EventuallyPersistentStore *s, Dispatcher *d, EPStats &st) :
        store(s), dispatcher(d), stats(st) {}

    void start(void);
    void stop(void);
    bool run(TaskId tid);
    bool pendingJob(void) {
        return numRemainingItems > 0;
    }

    void notifyBGEvent(void) {
        if (++numRemainingItems == 1) {
            LockHolder lh(taskMutex);
            assert(task.get());
            dispatcher->wake(task, &task);
        }
    }

private:
    void doFetch(uint16_t vbId);
    void clearItems(void);

    EventuallyPersistentStore *store;
    Dispatcher *dispatcher;
    vb_bgfetch_queue_t items2fetch;
    TaskId task;
    Mutex taskMutex;
    EPStats &stats;
    Atomic<size_t> numRemainingItems;
};

#endif /* BGFETCHER_HH */