/* CV for waking up the queue. */
    std::condition_variable queueMonitorWakeup;
    std::mutex queueMonitorMutex;

    void getQueuedBuilds(std::shared_ptr<StoreAPI> store);

    void getQueuedBuilds(std::shared_ptr<StoreAPI> store, unsigned int & lastBuildId);

    auto conn(dbPool.get());
    struct receiver : public pqxx::notification_receiver
    {
        bool status = false;
        receiver(pqxx::connection_base & c, const std::string & channel)
            : pqxx::notification_receiver(c, channel) { }
        void operator() (const string & payload, int pid) override
        {
            status = true;
        };
        bool get() {
            bool b = status;
            status = false;
            return b;
        }
    };
    receiver buildsAdded(*conn, "builds_added");
    receiver buildsRestarted(*conn, "builds_restarted");
    receiver buildsCancelled(*conn, "builds_cancelled");

    unsigned int lastBuildId = 0;

        getQueuedBuilds(store);

        getQueuedBuilds(store, lastBuildId);
        /* Sleep until we get notification from the database about an
           event. */
        conn->await_notification();

        {
            std::unique_lock<std::mutex> lock(queueMonitorMutex);
            queueMonitorWakeup.wait_for(lock, std::chrono::seconds(5));

        if (buildsAdded.get())
            printMsg(lvlError, "got notification: new builds added to the queue");
        if (buildsRestarted.get()) {
            printMsg(lvlError, "got notification: builds restarted");
            lastBuildId = 0; // check all builds
        }
        if (buildsCancelled.get()) {
            printMsg(lvlError, "got notification: builds cancelled");

void State::getQueuedBuilds(std::shared_ptr<StoreAPI> store)

void State::getQueuedBuilds(std::shared_ptr<StoreAPI> store, unsigned int & lastBuildId)

    printMsg(lvlError, "checking the queue...");

    printMsg(lvlError, format("checking the queue for builds > %1%...") % lastBuildId);

        auto res = txn.exec("select * from Builds where finished = 0 order by id");

        auto res = txn.parameterized("select * from Builds where id > $1 and finished = 0 order by id")(lastBuildId).exec();

            if (id > lastBuildId) lastBuildId = id;

        R * operator -> () { return r; }

        R * operator -> () { return r.get(); }

        $db->storage->dbh->do("notify builds_restarted");

        $db->storage->dbh->do("notify builds_added");