C++ CursorCache类代码示例

 bool run(OperationContext* txn,
          const string&,
          BSONObj& jsobj,
          int,
          string& errmsg,
          BSONObjBuilder& result) {
     cursorCache.appendInfo( result );
     if ( jsobj["setTimeout"].isNumber() )
         CursorCache::TIMEOUT = jsobj["setTimeout"].numberLong();
     return true;
 }

 bool run(const string&, BSONObj& jsobj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
     cursorCache.appendInfo( result );
     if ( jsobj["setTimeout"].isNumber() )
         CursorCache::TIMEOUT = jsobj["setTimeout"].numberLong();
     return true;
 }

//.........这里部分代码省略.........
                break;
            }

            if ( docCount == ntoreturn ) {
                // soft limit aka batch size
                break;
            }

            if ( ntoreturn == 0 && _totalSent == 0 && docCount >= 100 ) {
                // first batch should be max 100 unless batch size specified
                break;
            }
        }

        bool hasMore = sendMore && _cursor->more();

        LOG(5) << "\t hasMore: " << hasMore
               << " sendMore: " << sendMore
               << " cursorMore: " << _cursor->more()
               << " ntoreturn: " << ntoreturn
               << " num: " << docCount
               << " wouldSendMoreIfHad: " << sendMore
               << " id:" << getId()
               << " totalSent: " << _totalSent << endl;

        _totalSent += docCount;
        _done = ! hasMore;

        return hasMore;
    }

    // ---- CursorCache -----

    long long CursorCache::TIMEOUT = 600000;

    unsigned getCCRandomSeed() {
        scoped_ptr<SecureRandom> sr( SecureRandom::create() );
        return sr->nextInt64();
    }

    CursorCache::CursorCache()
        :_mutex( "CursorCache" ),
         _random( getCCRandomSeed() ),
         _shardedTotal(0) {
    }

    CursorCache::~CursorCache() {
        // TODO: delete old cursors?
        bool print = logLevel > 0;
        if ( _cursors.size() || _refs.size() )
            print = true;
        verify(_refs.size() == _refsNS.size());
        
        if ( print ) 
            cout << " CursorCache at shutdown - "
                 << " sharded: " << _cursors.size()
                 << " passthrough: " << _refs.size()
                 << endl;
    }

    ShardedClientCursorPtr CursorCache::get( long long id ) const {
        LOG(_myLogLevel) << "CursorCache::get id: " << id << endl;
        scoped_lock lk( _mutex );
        MapSharded::const_iterator i = _cursors.find( id );
        if ( i == _cursors.end() ) {
            OCCASIONALLY log() << "Sharded CursorCache missing cursor id: " << id << endl;

//.........这里部分代码省略.........
    //  is stored in 'sendMoreBatches'.
    //
    //  2. The last call to _cursor->more() was true (i.e. we never explicitly got a false
    //  value from _cursor->more()). This condition is stored in 'cursorHasMore'. If the server
    //  hits EOF while executing a query or a getmore, it will pass a cursorId of 0 in the
    //  query response to indicate that there are no more results. In this case, _cursor->more()
    //  will be explicitly false, and we know for sure that we do not have to send more batches.
    //
    //  On the other hand, if _cursor->more() is true there may or may not be more results.
    //  Suppose that the mongod generates enough results to fill this batch. In this case it
    //  does not know whether not there are more, because doing so would require requesting an
    //  extra result and seeing whether we get EOF. The mongod sends a valid cursorId to
    //  indicate that there may be more. We do the same here: we indicate that there may be
    //  more results to retrieve by setting 'hasMoreBatches' to true.
    bool hasMoreBatches = sendMoreBatches && cursorHasMore;

    LOG(5) << "\t hasMoreBatches: " << hasMoreBatches << " sendMoreBatches: " << sendMoreBatches
           << " cursorHasMore: " << cursorHasMore << " batchSize: " << batchSize
           << " num: " << docCount << " id:" << getId() << " totalSent: " << _totalSent << endl;

    _totalSent += docCount;
    _done = !hasMoreBatches;

    return hasMoreBatches;
}

// ---- CursorCache -----

unsigned getCCRandomSeed() {
    unique_ptr<SecureRandom> sr(SecureRandom::create());
    return sr->nextInt64();
}

CursorCache::CursorCache() : _random(getCCRandomSeed()), _shardedTotal(0) {}

CursorCache::~CursorCache() {
    // TODO: delete old cursors?
    bool print = shouldLog(logger::LogSeverity::Debug(1));
    if (_cursors.size() || _refs.size())
        print = true;
    verify(_refs.size() == _refsNS.size());

    if (print)
        log() << " CursorCache at shutdown - "
              << " sharded: " << _cursors.size() << " passthrough: " << _refs.size() << endl;
}

ShardedClientCursorPtr CursorCache::get(long long id) const {
    LOG(_myLogLevel) << "CursorCache::get id: " << id << endl;
    stdx::lock_guard<stdx::mutex> lk(_mutex);
    MapSharded::const_iterator i = _cursors.find(id);
    if (i == _cursors.end()) {
        return ShardedClientCursorPtr();
    }
    i->second->accessed();
    return i->second;
}

int CursorCache::getMaxTimeMS(long long id) const {
    verify(id);
    stdx::lock_guard<stdx::mutex> lk(_mutex);
    MapShardedInt::const_iterator i = _cursorsMaxTimeMS.find(id);
    return (i != _cursorsMaxTimeMS.end()) ? i->second : 0;
}

void CursorCache::store(ShardedClientCursorPtr cursor, int maxTimeMS) {

namespace mongo {

    // --------  ShardedCursor -----------

    ShardedClientCursor::ShardedClientCursor( QueryMessage& q , ClusteredCursor * cursor ) {
        assert( cursor );
        _cursor = cursor;

        _skip = q.ntoskip;
        _ntoreturn = q.ntoreturn;

        _totalSent = 0;
        _done = false;

        _id = 0;

        if ( q.queryOptions & QueryOption_NoCursorTimeout ) {
            _lastAccessMillis = 0;
        }
        else
            _lastAccessMillis = Listener::getElapsedTimeMillis();
    }

    ShardedClientCursor::~ShardedClientCursor() {
        assert( _cursor );
        delete _cursor;
        _cursor = 0;
    }

    long long ShardedClientCursor::getId() {
        if ( _id <= 0 ) {
            _id = cursorCache.genId();
            assert( _id >= 0 );
        }
        return _id;
    }

    void ShardedClientCursor::accessed() {
        if ( _lastAccessMillis > 0 )
            _lastAccessMillis = Listener::getElapsedTimeMillis();
    }

    long long ShardedClientCursor::idleTime( long long now ) {
        if ( _lastAccessMillis == 0 )
            return 0;
        return now - _lastAccessMillis;
    }

    bool ShardedClientCursor::sendNextBatch( Request& r , int ntoreturn ) {
        uassert( 10191 ,  "cursor already done" , ! _done );

        int maxSize = 1024 * 1024;
        if ( _totalSent > 0 )
            maxSize *= 3;

        BufBuilder b(32768);

        int num = 0;

        // Send more if ntoreturn is 0, or any value > 1 (one is assumed to be a single doc return, with no cursor)
        bool sendMore = ntoreturn == 0 || ntoreturn > 1;
        ntoreturn = abs( ntoreturn );

        while ( _cursor->more() ) {
            BSONObj o = _cursor->next();

            b.appendBuf( (void*)o.objdata() , o.objsize() );
            num++;

            if ( b.len() > maxSize ) {
                break;
            }

            if ( num == ntoreturn ) {
                // soft limit aka batch size
                break;
            }

            if ( ntoreturn == 0 && _totalSent == 0 && num >= 100 ) {
                // first batch should be max 100 unless batch size specified
                break;
            }
        }

        bool hasMore = sendMore && _cursor->more();
        LOG(5) << "\t hasMore: " << hasMore << " sendMore: " << sendMore << " cursorMore: " << _cursor->more() << " ntoreturn: " << ntoreturn
               << " num: " << num << " wouldSendMoreIfHad: " << sendMore << " id:" << getId() << " totalSent: " << _totalSent << endl;

        replyToQuery( 0 , r.p() , r.m() , b.buf() , b.len() , num , _totalSent , hasMore ? getId() : 0 );
        _totalSent += num;
        _done = ! hasMore;

        return hasMore;
    }

    // ---- CursorCache -----

    long long CursorCache::TIMEOUT = 600000;

    CursorCache::CursorCache()
//.........这里部分代码省略.........

//.........这里部分代码省略.........
        //  1. ntoreturn is positive and not equal to 1 (see the comment above). This condition
        //  is stored in 'sendMoreBatches'.
        //
        //  2. The last call to _cursor->more() was true (i.e. we never explicitly got a false
        //  value from _cursor->more()). This condition is stored in 'cursorHasMore'. If the server
        //  hits EOF while executing a query or a getmore, it will pass a cursorId of 0 in the
        //  query response to indicate that there are no more results. In this case, _cursor->more()
        //  will be explicitly false, and we know for sure that we do not have to send more batches.
        //
        //  On the other hand, if _cursor->more() is true there may or may not be more results.
        //  Suppose that the mongod generates enough results to fill this batch. In this case it
        //  does not know whether not there are more, because doing so would require requesting an
        //  extra result and seeing whether we get EOF. The mongod sends a valid cursorId to
        //  indicate that there may be more. We do the same here: we indicate that there may be
        //  more results to retrieve by setting 'hasMoreBatches' to true.
        bool hasMoreBatches = sendMoreBatches && cursorHasMore;

        LOG(5) << "\t hasMoreBatches: " << hasMoreBatches
               << " sendMoreBatches: " << sendMoreBatches
               << " cursorHasMore: " << cursorHasMore
               << " ntoreturn: " << ntoreturn
               << " num: " << docCount
               << " id:" << getId()
               << " totalSent: " << _totalSent << endl;

        _totalSent += docCount;
        _done = ! hasMoreBatches;

        return hasMoreBatches;
    }

    // ---- CursorCache -----

    long long CursorCache::TIMEOUT = 600000;

    unsigned getCCRandomSeed() {
        scoped_ptr<SecureRandom> sr( SecureRandom::create() );
        return sr->nextInt64();
    }

    CursorCache::CursorCache()
        :_mutex( "CursorCache" ),
         _random( getCCRandomSeed() ),
         _shardedTotal(0) {
    }

    CursorCache::~CursorCache() {
        // TODO: delete old cursors?
        bool print = logger::globalLogDomain()->shouldLog(logger::LogSeverity::Debug(1));
        if ( _cursors.size() || _refs.size() )
            print = true;
        verify(_refs.size() == _refsNS.size());
        
        if ( print ) 
            log() << " CursorCache at shutdown - "
                  << " sharded: " << _cursors.size()
                  << " passthrough: " << _refs.size()
                  << endl;
    }

    ShardedClientCursorPtr CursorCache::get( long long id ) const {
        LOG(_myLogLevel) << "CursorCache::get id: " << id << endl;
        scoped_lock lk( _mutex );
        MapSharded::const_iterator i = _cursors.find( id );
        if ( i == _cursors.end() ) {
            return ShardedClientCursorPtr();

 virtual void doWork() {
     cursorCache.doTimeouts();
 }