C++ OplogReader::tailCheck方法代码示例

    void BackgroundSync::produce() {
        // this oplog reader does not do a handshake because we don't want the server it's syncing
        // from to track how far it has synced
        OplogReader r;
        OpTime lastOpTimeFetched;
        // find a target to sync from the last op time written
        getOplogReader(r);

        // no server found
        {
            boost::unique_lock<boost::mutex> lock(_mutex);

            if (_currentSyncTarget == NULL) {
                lock.unlock();
                sleepsecs(1);
                // if there is no one to sync from
                return;
            }
            lastOpTimeFetched = _lastOpTimeFetched;
        }

        r.tailingQueryGTE(rsoplog, lastOpTimeFetched);

        // if target cut connections between connecting and querying (for
        // example, because it stepped down) we might not have a cursor
        if (!r.haveCursor()) {
            return;
        }

        uassert(1000, "replSet source for syncing doesn't seem to be await capable -- is it an older version of mongodb?", r.awaitCapable() );

        if (isRollbackRequired(r)) {
            stop();
            return;
        }

        while (!inShutdown()) {
            if (!r.moreInCurrentBatch()) {
                // Check some things periodically
                // (whenever we run out of items in the
                // current cursor batch)

                int bs = r.currentBatchMessageSize();
                if( bs > 0 && bs < BatchIsSmallish ) {
                    // on a very low latency network, if we don't wait a little, we'll be 
                    // getting ops to write almost one at a time.  this will both be expensive
                    // for the upstream server as well as potentially defeating our parallel 
                    // application of batches on the secondary.
                    //
                    // the inference here is basically if the batch is really small, we are 
                    // "caught up".
                    //
                    dassert( !Lock::isLocked() );
                    sleepmillis(SleepToAllowBatchingMillis);
                }
  
                if (theReplSet->gotForceSync()) {
                    return;
                }
                // If we are transitioning to primary state, we need to leave
                // this loop in order to go into bgsync-pause mode.
                if (isAssumingPrimary() || theReplSet->isPrimary()) {
                    return;
                }

                // re-evaluate quality of sync target
                if (shouldChangeSyncTarget()) {
                    return;
                }


                {
                    //record time for each getmore
                    TimerHolder batchTimer(&getmoreReplStats);
                    
                    // This calls receiveMore() on the oplogreader cursor.
                    // It can wait up to five seconds for more data.
                    r.more();
                }
                networkByteStats.increment(r.currentBatchMessageSize());

                if (!r.moreInCurrentBatch()) {
                    // If there is still no data from upstream, check a few more things
                    // and then loop back for another pass at getting more data
                    {
                        boost::unique_lock<boost::mutex> lock(_mutex);
                        if (_pause || 
                            !_currentSyncTarget || 
                            !_currentSyncTarget->hbinfo().hbstate.readable()) {
                            return;
                        }
                    }

                    r.tailCheck();
                    if( !r.haveCursor() ) {
                        LOG(1) << "replSet end syncTail pass" << rsLog;
                        return;
                    }

                    continue;
//.........这里部分代码省略.........