Cursor is closed ?

[Mika Saari]

Hi,

  What could be reason for error below?

  Thanks a lot,

     -Mika

  MongoDB 3.2

  mongod 1-shard, 3-replicas (replicas each in different VM)

  mongod configsrv 3-replicas (repicas each in different VM)

  mongos 3 pieces (each router in different VM)

  NodeJS mongodb(2.2.11) and mongodb-core(2.0.13)

  MongoError: Cursor is closed

    at Function.MongoError.create (/home/manager/service/node_modules/mongodb-core/lib/error.js:31:11)

    at Cursor.skip (/home/manager/service/node_modules/mongodb/lib/cursor.js:623:102)

    at /home/manager/service/routes/system-ops.js:56:32

    at /home/manager/service/node_modules/async/dist/async.js:1156:9

    at replenish (/home/manager/service/node_modules/async/dist/async.js:1030:17)

    at iterateeCallback (/home/manager/service/node_modules/async/dist/async.js:1015:17)

    at /home/manager/service/node_modules/async/dist/async.js:988:16

    at /home/manager/service/node_modules/async/dist/async.js:1158:13

    at /home/manager/service/routes/system-ops.js:62:33

    at handleCallback (/home/manager/service/node_modules/mongodb/lib/utils.js:96:56)

  Code snippet:

        db.collection('node').find({layer: layer}, {_id: 1}).each(function(err, node) {
            if(err) {
                console.log("ERROR: node.find()");
            }


            if(node == null) {
                return reply([]);
            }


            var nid = ObjectID(node._id).toString();
            db.collection('ops_log').find({nodeId:nid, ts:{$gte: tsStart, $lte: tsEnd}}).count(function(err, total) {
                if(err) {
                    return reply([]);
                }


                db.collection('ops_log').find({nodeId: nid, ts:{$gte: tsStart ,$lte: tsEnd}}, {_id: 0, date: 0, nodeId: 0}, function(err, cursor) {
                    if(err) {
                        console.log("ERROR: ops_log.find():",err);
                    }


                    async.timesSeries(total/ps, function(cnt, next) {
                        cursor.skip(cnt*ps).limit(ps).each(function(err, item) {
                            if(err) {
                                return next(err, cnt);
                            }


                            if(item == null) {
                                next(err, cnt);
                            }
                        });
                    },
                    function(err, counter) {
                        if(err) {
                            console.log("ERROR: in the skip,limit,sort FINAL:",counter, err);
                        }
                        console.log("EACH DONE");
                    });
                });
            });
        });

[Mika Saari]

Hi,

  I have been wresting this problem much more now, but seems that I can not get around it. If I limit the query to return only 100 documents, I won't get the Cursor not found error anymore, but 100 docs is not enough for one find unfortunately. 

  Could the multiple routers, replicas, config servers cause this kind of problem ?

   I will try coding this same small test application in C and see if it has effect.

   Thanks for any tips,

    -Mika

[Christian Kvalheim]

Are you attempting to load-balance the mongos proxies through some other load-balancer ? Cursors only exist in the context of a mongos instance so if you are load-balancing you will see these issues as the different getMore's goes to other mongos proxies that don't know about the cursor id.

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