mobile_session_pool.h

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#pragma once

#include <queue>
#include <sqlite3.h>
#include <string>
#include <vector>

#include "mongo/base/disallow_copying.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/storage/mobile/mobile_session.h"
#include "mongo/stdx/mutex.h"

namespace mongo {
class MobileSession;

class MobileDelayedOpQueue final {
    MONGO_DISALLOW_COPYING(MobileDelayedOpQueue);

public:
    MobileDelayedOpQueue();
    void enqueueOp(std::string& opQuery);
    void execAndDequeueOp(MobileSession* session);
    void execAndDequeueAllOps(MobileSession* session);
    bool isEmpty();

private:
    AtomicBool _isEmpty;
    stdx::mutex _queueMutex;
    std::queue<std::string> _opQueryQueue;
};

class MobileSessionPool final {
    MONGO_DISALLOW_COPYING(MobileSessionPool);

public:
    MobileSessionPool(const std::string& path, std::uint64_t maxPoolSize = 80);

    ~MobileSessionPool();

    std::unique_ptr<MobileSession> getSession(OperationContext* opCtx);

    void releaseSession(MobileSession* session);

    void shutDown();

    // Failed drops get queued here and get re-tried periodically
    MobileDelayedOpQueue failedDropsQueue;

private:
    sqlite3* _popSession_inlock();

    // This is used to lock the _sessions vector.
    stdx::mutex _mutex;
    stdx::condition_variable _releasedSessionNotifier;

    std::string _path;

    std::uint64_t _maxPoolSize = 80;
    std::uint64_t _curPoolSize = 0;
    bool _shuttingDown = false;

    using SessionPool = std::vector<sqlite3*>;
    SessionPool _sessions;
};
}  // namespace mongo