path: root/src/mongo/s/cursors.cpp

// cursors.cpp
/*
 *    Copyright (C) 2010 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects
 *    for all of the code used other than as permitted herein. If you modify
 *    file(s) with this exception, you may extend this exception to your
 *    version of the file(s), but you are not obligated to do so. If you do not
 *    wish to do so, delete this exception statement from your version. If you
 *    delete this exception statement from all source files in the program,
 *    then also delete it in the license file.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery

#include "mongo/platform/basic.h"

#include "mongo/s/cursors.h"

#include <boost/scoped_ptr.hpp>
#include <string>
#include <vector>

#include "mongo/base/data_cursor.h"
#include "mongo/db/audit.h"
#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/authorization_manager.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/commands.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/max_time.h"
#include "mongo/db/server_parameters.h"
#include "mongo/util/concurrency/task.h"
#include "mongo/util/log.h"
#include "mongo/util/net/listen.h"

namespace mongo {

    using boost::scoped_ptr;
    using std::endl;
    using std::string;
    using std::stringstream;

    const int ShardedClientCursor::INIT_REPLY_BUFFER_SIZE = 32768;

    // Note: There is no counter for shardedEver from cursorInfo since it is deprecated
    static Counter64 cursorStatsMultiTarget;
    static Counter64 cursorStatsSingleTarget;

    // Simple class to report the sum total open cursors = sharded + refs
    class CursorStatsSum {
    public:
        operator long long() const {
            return get();
        }
        long long get() const {
            return cursorStatsMultiTarget.get() + cursorStatsSingleTarget.get();
        }
    };

    static CursorStatsSum cursorStatsTotalOpen;

    static ServerStatusMetricField<Counter64> dCursorStatsMultiTarget( "cursor.open.multiTarget",
                                                                       &cursorStatsMultiTarget);
    static ServerStatusMetricField<Counter64> dCursorStatsSingleTarget( "cursor.open.singleTarget",
                                                                        &cursorStatsSingleTarget);
    static ServerStatusMetricField<CursorStatsSum> dCursorStatsTotalOpen( "cursor.open.total",
                                                                          &cursorStatsTotalOpen);


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

    ShardedClientCursor::ShardedClientCursor( QueryMessage& q,
                                              ParallelSortClusteredCursor * cursor ) {
        verify( 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();

        cursorStatsMultiTarget.increment();
    }

    ShardedClientCursor::~ShardedClientCursor() {
        verify( _cursor );
        delete _cursor;
        _cursor = 0;
        cursorStatsMultiTarget.decrement();
    }

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

    int ShardedClientCursor::getTotalSent() const {
        return _totalSent;
    }

    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(int ntoreturn, BufBuilder& buffer, int& docCount) {
        uassert( 10191 ,  "cursor already done" , ! _done );

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

        docCount = 0;

        // If ntoreturn is negative, it means that we should send up to -ntoreturn results
        // back to the client, and that we should only send a *single batch*. An ntoreturn of
        // 1 is also a special case which means "return up to 1 result in a single batch" (so
        // that +1 actually has the same meaning of -1). For all other values of ntoreturn, we
        // may have to return multiple batches.
        const bool sendMoreBatches = ntoreturn == 0 || ntoreturn > 1;
        ntoreturn = abs( ntoreturn );

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

            buffer.appendBuf( (void*)o.objdata() , o.objsize() );
            docCount++;
            // Ensure that the next batch will never wind up requesting more docs from the shard
            // than are remaining to satisfy the initial ntoreturn.
            if (ntoreturn != 0) {
                _cursor->setBatchSize(ntoreturn - docCount);
            }

            if ( buffer.len() > maxSize ) {
                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;
            }
        }

        // We need to request another batch if the following two conditions hold:
        //
        //  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 = 10 * 60 * 1000 /* 10 minutes */;
    ExportedServerParameter<long long> cursorCacheTimeoutConfig(ServerParameterSet::getGlobal(),
                                                                "cursorTimeoutMillis",
                                                                &CursorCache::TIMEOUT,
                                                                true, true);

    unsigned getCCRandomSeed() {
        scoped_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;
        boost::lock_guard<boost::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 );
        boost::lock_guard<boost::mutex> lk( _mutex );
        MapShardedInt::const_iterator i = _cursorsMaxTimeMS.find( id );
        return ( i != _cursorsMaxTimeMS.end() ) ? i->second : 0;
    }

    void CursorCache::store( ShardedClientCursorPtr cursor, int maxTimeMS ) {
        LOG(_myLogLevel) << "CursorCache::store cursor " << " id: " << cursor->getId()
            << (maxTimeMS != kMaxTimeCursorNoTimeLimit ? str::stream() << "maxTimeMS: " << maxTimeMS
                                                      : string(""))
            << endl;
        verify( cursor->getId() );
        verify( maxTimeMS == kMaxTimeCursorTimeLimitExpired
                || maxTimeMS == kMaxTimeCursorNoTimeLimit
                || maxTimeMS > 0 );
        boost::lock_guard<boost::mutex> lk( _mutex );
        _cursorsMaxTimeMS[cursor->getId()] = maxTimeMS;
        _cursors[cursor->getId()] = cursor;
        _shardedTotal++;
    }

    void CursorCache::updateMaxTimeMS( long long id, int maxTimeMS ) {
        verify( id );
        verify( maxTimeMS == kMaxTimeCursorTimeLimitExpired
                || maxTimeMS == kMaxTimeCursorNoTimeLimit
                || maxTimeMS > 0 );
        boost::lock_guard<boost::mutex> lk( _mutex );
        _cursorsMaxTimeMS[id] = maxTimeMS;
    }

    void CursorCache::remove( long long id ) {
        verify( id );
        boost::lock_guard<boost::mutex> lk( _mutex );
        _cursorsMaxTimeMS.erase( id );
        _cursors.erase( id );
    }
    
    void CursorCache::removeRef( long long id ) {
        verify( id );
        boost::lock_guard<boost::mutex> lk( _mutex );
        _refs.erase( id );
        _refsNS.erase( id );
        cursorStatsSingleTarget.decrement();
    }

    void CursorCache::storeRef(const std::string& server, long long id, const std::string& ns) {
        LOG(_myLogLevel) << "CursorCache::storeRef server: " << server << " id: " << id << endl;
        verify( id );
        boost::lock_guard<boost::mutex> lk( _mutex );
        _refs[id] = server;
        _refsNS[id] = ns;
        cursorStatsSingleTarget.increment();
    }

    string CursorCache::getRef( long long id ) const {
        verify( id );
        boost::lock_guard<boost::mutex> lk( _mutex );
        MapNormal::const_iterator i = _refs.find( id );

        LOG(_myLogLevel) << "CursorCache::getRef id: " << id << " out: " << ( i == _refs.end() ? " NONE " : i->second ) << endl;

        if ( i == _refs.end() )
            return "";
        return i->second;
    }

    std::string CursorCache::getRefNS(long long id) const {
        verify(id);
        boost::lock_guard<boost::mutex> lk(_mutex);
        MapNormal::const_iterator i = _refsNS.find(id);

        LOG(_myLogLevel) << "CursorCache::getRefNs id: " << id
                << " out: " << ( i == _refsNS.end() ? " NONE " : i->second ) << std::endl;

        if ( i == _refsNS.end() )
            return "";
        return i->second;
    }


    long long CursorCache::genId() {
        while ( true ) {
            boost::lock_guard<boost::mutex> lk( _mutex );

            long long x = Listener::getElapsedTimeMillis() << 32;
            x |= _random.nextInt32();

            if ( x == 0 )
                continue;

            if ( x < 0 )
                x *= -1;

            MapSharded::iterator i = _cursors.find( x );
            if ( i != _cursors.end() )
                continue;

            MapNormal::iterator j = _refs.find( x );
            if ( j != _refs.end() )
                continue;

            return x;
        }
    }

    void CursorCache::gotKillCursors(Message& m ) {
        DbMessage dbmessage(m);
        int n = dbmessage.pullInt();

        if ( n > 2000 ) {
            ( n < 30000 ? warning() : error() ) << "receivedKillCursors, n=" << n << endl;
        }

        uassert( 13286 , "sent 0 cursors to kill" , n >= 1 );
        uassert( 13287 , "too many cursors to kill" , n < 30000 );
        massert( 18632 , str::stream() << "bad kill cursors size: " << m.dataSize(), 
                    m.dataSize() == 8 + ( 8 * n ) );


        ConstDataCursor cursors(dbmessage.getArray(n));

        ClientBasic* client = ClientBasic::getCurrent();
        AuthorizationSession* authSession = AuthorizationSession::get(client);
        for ( int i=0; i<n; i++ ) {
            long long id = cursors.readAndAdvance<LittleEndian<int64_t>>();
            LOG(_myLogLevel) << "CursorCache::gotKillCursors id: " << id << endl;

            if ( ! id ) {
                warning() << " got cursor id of 0 to kill" << endl;
                continue;
            }

            string server;
            {
                boost::lock_guard<boost::mutex> lk( _mutex );

                MapSharded::iterator i = _cursors.find( id );
                if ( i != _cursors.end() ) {
                    Status authorizationStatus = authSession->checkAuthForKillCursors(
                            NamespaceString(i->second->getNS()), id);
                    audit::logKillCursorsAuthzCheck(
                            client,
                            NamespaceString(i->second->getNS()),
                            id,
                            authorizationStatus.isOK() ? ErrorCodes::OK : ErrorCodes::Unauthorized);
                    if (authorizationStatus.isOK()) {
                        _cursorsMaxTimeMS.erase( i->second->getId() );
                        _cursors.erase( i );
                    }
                    continue;
                }

                MapNormal::iterator refsIt = _refs.find(id);
                MapNormal::iterator refsNSIt = _refsNS.find(id);
                if (refsIt == _refs.end()) {
                    warning() << "can't find cursor: " << id << endl;
                    continue;
                }
                verify(refsNSIt != _refsNS.end());
                Status authorizationStatus = authSession->checkAuthForKillCursors(
                        NamespaceString(refsNSIt->second), id);
                audit::logKillCursorsAuthzCheck(
                        client,
                        NamespaceString(refsNSIt->second),
                        id,
                        authorizationStatus.isOK() ? ErrorCodes::OK : ErrorCodes::Unauthorized);
                if (!authorizationStatus.isOK()) {
                    continue;
                }
                server = refsIt->second;
                _refs.erase(refsIt);
                _refsNS.erase(refsNSIt);
                cursorStatsSingleTarget.decrement();
            }

            LOG(_myLogLevel) << "CursorCache::found gotKillCursors id: " << id << " server: " << server << endl;

            verify( server.size() );
            ScopedDbConnection conn(server);
            conn->killCursor( id );
            conn.done();
        }
    }

    void CursorCache::appendInfo( BSONObjBuilder& result ) const {
        boost::lock_guard<boost::mutex> lk( _mutex );
        result.append( "sharded", static_cast<int>(cursorStatsMultiTarget.get()));
        result.appendNumber( "shardedEver" , _shardedTotal );
        result.append( "refs", static_cast<int>(cursorStatsSingleTarget.get()));
        result.append( "totalOpen", static_cast<int>(cursorStatsTotalOpen.get()));
    }

    void CursorCache::doTimeouts() {
        long long now = Listener::getElapsedTimeMillis();
        boost::lock_guard<boost::mutex> lk( _mutex );
        for ( MapSharded::iterator i=_cursors.begin(); i!=_cursors.end(); ++i ) {
            // Note: cursors with no timeout will always have an idleTime of 0
            long long idleFor = i->second->idleTime( now );
            if ( idleFor < TIMEOUT ) {
                continue;
            }
            log() << "killing old cursor " << i->second->getId() << " idle for: " << idleFor << "ms" << endl; // TODO: make LOG(1)
            _cursorsMaxTimeMS.erase( i->second->getId() );
            _cursors.erase( i );
            i = _cursors.begin(); // possible 2nd entry will get skipped, will get on next pass
            if ( i == _cursors.end() )
                break;
        }
    }

    CursorCache cursorCache;

    const int CursorCache::_myLogLevel = 3;

    class CursorTimeoutTask : public task::Task {
    public:
        virtual string name() const { return "cursorTimeout"; }
        virtual void doWork() {
            cursorCache.doTimeouts();
        }
    };

    void CursorCache::startTimeoutThread() {
        task::repeat( new CursorTimeoutTask , 4000 );
    }

    class CmdCursorInfo : public Command {
    public:
        CmdCursorInfo() : Command( "cursorInfo" ) {}
        virtual bool slaveOk() const { return true; }
        virtual void help( stringstream& help ) const {
            help << " example: { cursorInfo : 1 }";
        }
        virtual void addRequiredPrivileges(const std::string& dbname,
                                           const BSONObj& cmdObj,
                                           std::vector<Privilege>* out) {
            ActionSet actions;
            actions.addAction(ActionType::cursorInfo);
            out->push_back(Privilege(ResourcePattern::forClusterResource(), actions));
        }
        virtual bool isWriteCommandForConfigServer() const { return false; }
        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;
        }
    } cmdCursorInfo;

}