C++ OplogReader::findOne方法代码示例

    BSONObj Sync::getMissingDoc(const BSONObj& o) {
        OplogReader missingObjReader;
        const char *ns = o.getStringField("ns");

        // capped collections
        NamespaceDetails *nsd = nsdetails(ns);
        if ( nsd && nsd->isCapped() ) {
            log() << "replication missing doc, but this is okay for a capped collection (" << ns << ")" << endl;
            return BSONObj();
        }

        uassert(15916, str::stream() << "Can no longer connect to initial sync source: " << hn, missingObjReader.connect(hn));

        // might be more than just _id in the update criteria
        BSONObj query = BSONObjBuilder().append(o.getObjectField("o2")["_id"]).obj();
        BSONObj missingObj;
        try {
            missingObj = missingObjReader.findOne(ns, query);
        } catch(DBException& e) {
            log() << "replication assertion fetching missing object: " << e.what() << endl;
            throw;
        }

        return missingObj;
    }

BSONObj SyncTail::getMissingDoc(OperationContext* txn, Database* db, const BSONObj& o) {
    OplogReader missingObjReader;  // why are we using OplogReader to run a non-oplog query?
    const char* ns = o.getStringField("ns");

    // capped collections
    Collection* collection = db->getCollection(ns);
    if (collection && collection->isCapped()) {
        log() << "missing doc, but this is okay for a capped collection (" << ns << ")";
        return BSONObj();
    }

    const int retryMax = 3;
    for (int retryCount = 1; retryCount <= retryMax; ++retryCount) {
        if (retryCount != 1) {
            // if we are retrying, sleep a bit to let the network possibly recover
            sleepsecs(retryCount * retryCount);
        }
        try {
            bool ok = missingObjReader.connect(HostAndPort(_hostname));
            if (!ok) {
                warning() << "network problem detected while connecting to the "
                          << "sync source, attempt " << retryCount << " of " << retryMax << endl;
                continue;  // try again
            }
        } catch (const SocketException&) {
            warning() << "network problem detected while connecting to the "
                      << "sync source, attempt " << retryCount << " of " << retryMax << endl;
            continue;  // try again
        }

        // get _id from oplog entry to create query to fetch document.
        const BSONElement opElem = o.getField("op");
        const bool isUpdate = !opElem.eoo() && opElem.str() == "u";
        const BSONElement idElem = o.getObjectField(isUpdate ? "o2" : "o")["_id"];

        if (idElem.eoo()) {
            severe() << "cannot fetch missing document without _id field: " << o.toString();
            fassertFailedNoTrace(28742);
        }

        BSONObj query = BSONObjBuilder().append(idElem).obj();
        BSONObj missingObj;
        try {
            missingObj = missingObjReader.findOne(ns, query);
        } catch (const SocketException&) {
            warning() << "network problem detected while fetching a missing document from the "
                      << "sync source, attempt " << retryCount << " of " << retryMax << endl;
            continue;  // try again
        } catch (DBException& e) {
            error() << "assertion fetching missing object: " << e.what() << endl;
            throw;
        }

        // success!
        return missingObj;
    }
    // retry count exceeded
    msgasserted(15916,
                str::stream() << "Can no longer connect to initial sync source: " << _hostname);
}

    void ReplSetImpl::syncTail() { 
        // todo : locking vis a vis the mgr...

        const Member *primary = box.getPrimary();
        if( primary == 0 ) return;
        string hn = primary->h().toString();
        OplogReader r;
        if( !r.connect(primary->h().toString()) ) { 
            log(2) << "replSet can't connect to " << hn << " to read operations" << rsLog;
            return;
        }

        /* first make sure we are not hopelessly out of sync by being very stale. */
        {
            BSONObj remoteOldestOp = r.findOne(rsoplog, Query());
            OpTime ts = remoteOldestOp["ts"]._opTime();
            DEV log() << "remoteOldestOp: " << ts.toStringPretty() << endl;
            else log(3) << "remoteOldestOp: " << ts.toStringPretty() << endl;
            if( lastOpTimeWritten < ts ) { 
                log() << "replSet error too stale to catch up, at least from primary " << hn << rsLog;
                log() << "replSet our last optime : " << lastOpTimeWritten.toStringPretty() << rsLog;
                log() << "replSet oldest at " << hn << " : " << ts.toStringPretty() << rsLog;
                log() << "replSet See http://www.mongodb.org/display/DOCS/Resyncing+a+Very+Stale+Replica+Set+Member" << rsLog;
                sethbmsg("error too stale to catch up");
                sleepsecs(120);
                return;
            }
        }

    BSONObj Sync::getMissingDoc(OperationContext* txn, Database* db, const BSONObj& o) {
        OplogReader missingObjReader; // why are we using OplogReader to run a non-oplog query?
        const char *ns = o.getStringField("ns");

        // capped collections
        Collection* collection = db->getCollection(ns);
        if ( collection && collection->isCapped() ) {
            log() << "replication missing doc, but this is okay for a capped collection (" << ns << ")" << endl;
            return BSONObj();
        }

        const int retryMax = 3;
        for (int retryCount = 1; retryCount <= retryMax; ++retryCount) {
            if (retryCount != 1) {
                // if we are retrying, sleep a bit to let the network possibly recover
                sleepsecs(retryCount * retryCount);
            }
            try {
                bool ok = missingObjReader.connect(HostAndPort(hn));
                if (!ok) {
                    warning() << "network problem detected while connecting to the "
                              << "sync source, attempt " << retryCount << " of "
                              << retryMax << endl;
                        continue;  // try again
                }
            } 
            catch (const SocketException&) {
                warning() << "network problem detected while connecting to the "
                          << "sync source, attempt " << retryCount << " of "
                          << retryMax << endl;
                continue; // try again
            }

            // might be more than just _id in the update criteria
            BSONObj query = BSONObjBuilder().append(o.getObjectField("o2")["_id"]).obj();
            BSONObj missingObj;
            try {
                missingObj = missingObjReader.findOne(ns, query);
            } 
            catch (const SocketException&) {
                warning() << "network problem detected while fetching a missing document from the "
                          << "sync source, attempt " << retryCount << " of "
                          << retryMax << endl;
                continue; // try again
            } 
            catch (DBException& e) {
                log() << "replication assertion fetching missing object: " << e.what() << endl;
                throw;
            }

            // success!
            return missingObj;
        }
        // retry count exceeded
        msgasserted(15916, 
                    str::stream() << "Can no longer connect to initial sync source: " << hn);
    }

    bool BackgroundSync::isStale(OpTime lastOpTimeFetched, 
                                 OplogReader& r, 
                                 BSONObj& remoteOldestOp) {
        remoteOldestOp = r.findOne(rsoplog, Query());
        OpTime remoteTs = remoteOldestOp["ts"]._opTime();
        {
            boost::unique_lock<boost::mutex> lock(_mutex);

            if (lastOpTimeFetched >= remoteTs) {
                return false;
            }
            log() << "replSet remoteOldestOp:    " << remoteTs.toStringLong() << rsLog;
            log() << "replSet lastOpTimeFetched: " << lastOpTimeFetched.toStringLong() << rsLog;
        }

        return true;
    }

 /**
  * Checks if the oplog given is too far ahead to read from.
  *
  * @param r the oplog
  * @param hn the hostname (for log messages)
  *
  * @return if we are stale compared to the oplog on hn
  */
 bool ReplSetImpl::_isStale(OplogReader& r, const string& hn) {
     BSONObj remoteOldestOp = r.findOne(rsoplog, Query());
     OpTime ts = remoteOldestOp["ts"]._opTime();
     DEV log() << "replSet remoteOldestOp:    " << ts.toStringLong() << rsLog;
     else log(3) << "replSet remoteOldestOp: " << ts.toStringLong() << rsLog;

    bool ReplSetImpl::_initialSyncOplogApplication(OplogReader& r, const Member *source,
        const OpTime& applyGTE, const OpTime& minValid) {

        const string hn = source->fullName();
        OplogReader missingObjReader;
        try {
            r.tailingQueryGTE( rsoplog, applyGTE );
            if ( !r.haveCursor() ) {
                log() << "replSet initial sync oplog query error" << rsLog;
                return false;
            }

            {
                if( !r.more() ) {
                    sethbmsg("replSet initial sync error reading remote oplog");
                    log() << "replSet initial sync error remote oplog (" << rsoplog << ") on host " << hn << " is empty?" << rsLog;
                    return false;
                }
                bo op = r.next();
                OpTime t = op["ts"]._opTime();
                r.putBack(op);

                if( op.firstElementFieldName() == string("$err") ) {
                    log() << "replSet initial sync error querying " << rsoplog << " on " << hn << " : " << op.toString() << rsLog;
                    return false;
                }

                uassert( 13508 , str::stream() << "no 'ts' in first op in oplog: " << op , !t.isNull() );
                if( t > applyGTE ) {
                    sethbmsg(str::stream() << "error " << hn << " oplog wrapped during initial sync");
                    log() << "replSet initial sync expected first optime of " << applyGTE << rsLog;
                    log() << "replSet initial sync but received a first optime of " << t << " from " << hn << rsLog;
                    return false;
                }

                sethbmsg(str::stream() << "initial oplog application from " << hn << " starting at "
                         << t.toStringPretty() << " to " << minValid.toStringPretty());
            }
        }
        catch(DBException& e) {
            log() << "replSet initial sync failing: " << e.toString() << rsLog;
            return false;
        }

        /* we lock outside the loop to avoid the overhead of locking on every operation. */
        writelock lk("");

        // todo : use exhaust
        OpTime ts;
        time_t start = time(0);
        unsigned long long n = 0;
        while( 1 ) {
            try {
                if( !r.more() )
                    break;
                BSONObj o = r.nextSafe(); /* note we might get "not master" at some point */
                ts = o["ts"]._opTime();

                {
                    if( (source->state() != MemberState::RS_PRIMARY &&
                            source->state() != MemberState::RS_SECONDARY) ||
                            replSetForceInitialSyncFailure ) {

                        int f = replSetForceInitialSyncFailure;
                        if( f > 0 ) {
                            replSetForceInitialSyncFailure = f-1;
                            log() << "replSet test code invoked, replSetForceInitialSyncFailure" << rsLog;
                            throw DBException("forced error",0);
                        }
                        log() << "replSet we are now primary" << rsLog;
                        throw DBException("primary changed",0);
                    }

                    if( ts >= applyGTE ) { // optimes before we started copying need not be applied.
                        bool failedUpdate = syncApply(o);
                        if( failedUpdate ) {
                            // we don't have the object yet, which is possible on initial sync.  get it.
                            log() << "replSet info adding missing object" << endl; // rare enough we can log
                            if( !missingObjReader.connect(hn) ) { // ok to call more than once
                                log() << "replSet initial sync fails, couldn't connect to " << hn << endl;
                                return false;
                            }
                            const char *ns = o.getStringField("ns");
                            BSONObj query = BSONObjBuilder().append(o.getObjectField("o2")["_id"]).obj(); // might be more than just _id in the update criteria
                            BSONObj missingObj;
                            try {
                                missingObj = missingObjReader.findOne(
                                    ns, 
                                    query );
                            } catch(...) { 
                                log() << "replSet assertion fetching missing object" << endl;
                                throw;
                            }
                            if( missingObj.isEmpty() ) { 
                                log() << "replSet missing object not found on source. presumably deleted later in oplog" << endl;
                                log() << "replSet o2: " << o.getObjectField("o2").toString() << endl;
                                log() << "replSet o firstfield: " << o.getObjectField("o").firstElementFieldName() << endl;
                            }
                            else {
                                Client::Context ctx(ns);
//.........这里部分代码省略.........

 bool ReplSetImpl::_isStale(OplogReader& r, const OpTime& startTs, BSONObj& remoteOldestOp) {
     remoteOldestOp = r.findOne(rsoplog, Query());
     OpTime remoteTs = remoteOldestOp["ts"]._opTime();
     DEV log() << "replSet remoteOldestOp:    " << remoteTs.toStringLong() << rsLog;
     else LOG(3) << "replSet remoteOldestOp: " << remoteTs.toStringLong() << rsLog;