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Parse Server for Node.js / Express
https://parseplatform.org
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"MongoError: Cursor not found" on relational query #5226

Closed mrmarcsmith closed 5 years ago

mrmarcsmith commented 5 years ago

Issue Description

This iOS query to get users of a certain role always return a "MongoError: Cursor not found" error

PFRole *role = [PFRole objectWithoutDataWithObjectId:@"mYoBjEcTId"]; // this is the _id of the  "Role"
    PFRelation *rel = [role relationForKey:@"users"];
    PFQuery *userQuery = rel.query;
    [userQuery whereKey:@"group" equalTo:"myGroup"];

Steps to reproduce

  1. set up server and database
  2. create a role
  3. add users to the role
  4. run the above query

Expected Results

The query returns users who are apart of the given role.

Actual Outcome

An internal server error is thrown and nothing is returned

Environment Setup

Logs/Trace

verbose: REQUEST for [GET] /parse/classes/_Role: {
  "where": {
    "districtNumber": 1,
    "$relatedTo": {
      "key": "users",
      "object": {
        "__type": "Pointer",
        "className": "_Role",
        "objectId": "xyz"
      }
    },
    "automaticSearchString": {
      "$regex": "\\Qa\\E"
    }
  },
  "redirectClassNameForKey": "users"
} method=GET, url=/parse/classes/_Role, x-real-ip=1.2.3.4, x-forwarded-for=1.2.3.4, x-nginx-proxy=true, host=my.example.com, connection=close, content-length=228, x-parse-client-version=i1.16.0, accept=*/*, x-parse-session-token=r:123, x-parse-application-id=123, x-parse-client-key=123, x-parse-installation-id=123, x-parse-os-version=12.0 (16A366), accept-language=en-us, accept-encoding=br, gzip, deflate, content-type=application/json; charset=utf-8, user-agent=E%20Busy%20Bees%20Babysitting/11397 CFNetwork/974.2.1 Darwin/18.0.0, x-parse-app-build-version=11397, x-parse-app-display-version=14.1.0, districtNumber=1, key=users, __type=Pointer, className=_Role, objectId=123, $regex=\Qa\E, redirectClassNameForKey=users
error: Error generating response. { MongoError: Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886).
    at /parse-server/node_modules/mongodb-core/lib/connection/pool.js:595:61
    at authenticateStragglers (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:513:16)
    at Connection.messageHandler (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:549:5)
    at emitMessageHandler (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:309:10)
    at TLSSocket.<anonymous> (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:452:17)
    at emitOne (events.js:96:13)
    at TLSSocket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at TLSSocket.Readable.push (_stream_readable.js:134:10)
    at TLSWrap.onread (net.js:559:20)
  name: 'MongoError',
  message: 'Cursor not found (namespace: \'parsedata._Join:users:_Role\', id: 3314076861576347886).',
  ok: 0,
  errmsg: 'Cursor not found (namespace: \'parsedata._Join:users:_Role\', id: 3314076861576347886).',
  code: 43,
  codeName: 'CursorNotFound',
  operationTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1544077155 },
  '$clusterTime': 
   { clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1544077155 },
     signature: { hash: [Object], keyId: [Object] } } } name=MongoError, message=Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886)., ok=0, errmsg=Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886)., code=43, codeName=CursorNotFound, _bsontype=Timestamp, low_=2, high_=1544077155, _bsontype=Timestamp, low_=2, high_=1544077155, _bsontype=Binary, sub_type=0, position=20, 0=58, 1=138, 2=88, 3=45, 4=70, 5=37, 6=153, 7=43, 8=160, 9=55, 10=29, 11=11, 12=12, 13=220, 14=202, 15=251, 16=186, 17=194, 18=246, 19=177, _bsontype=Long, low_=18, high_=1540979722
error: Uncaught internal server error. { MongoError: Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886).
    at /parse-server/node_modules/mongodb-core/lib/connection/pool.js:595:61
    at authenticateStragglers (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:513:16)
    at Connection.messageHandler (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:549:5)
    at emitMessageHandler (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:309:10)
    at TLSSocket.<anonymous> (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:452:17)
    at emitOne (events.js:96:13)
    at TLSSocket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at TLSSocket.Readable.push (_stream_readable.js:134:10)
    at TLSWrap.onread (net.js:559:20)
  name: 'MongoError',
  message: 'Cursor not found (namespace: \'parsedata._Join:users:_Role\', id: 3314076861576347886).',
  ok: 0,
  errmsg: 'Cursor not found (namespace: \'parsedata._Join:users:_Role\', id: 3314076861576347886).',
  code: 43,
  codeName: 'CursorNotFound',
  operationTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1544077155 },
  '$clusterTime': 
   { clusterTime: Timestamp { _bsontype: 'Timestamp', low_: 2, high_: 1544077155 },
     signature: { hash: [Object], keyId: [Object] } } } MongoError: Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886).
    at /parse-server/node_modules/mongodb-core/lib/connection/pool.js:595:61
    at authenticateStragglers (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:513:16)
    at Connection.messageHandler (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:549:5)
    at emitMessageHandler (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:309:10)
    at TLSSocket.<anonymous> (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:452:17)
    at emitOne (events.js:96:13)
    at TLSSocket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at TLSSocket.Readable.push (_stream_readable.js:134:10)
    at TLSWrap.onread (net.js:559:20)
MongoError: Cursor not found (namespace: 'parsedata._Join:users:_Role', id: 3314076861576347886).
    at /parse-server/node_modules/mongodb-core/lib/connection/pool.js:595:61
    at authenticateStragglers (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:513:16)
    at Connection.messageHandler (/parse-server/node_modules/mongodb-core/lib/connection/pool.js:549:5)
    at emitMessageHandler (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:309:10)
    at TLSSocket.<anonymous> (/parse-server/node_modules/mongodb-core/lib/connection/connection.js:452:17)
    at emitOne (events.js:96:13)
    at TLSSocket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at TLSSocket.Readable.push (_stream_readable.js:134:10)
    at TLSWrap.onread (net.js:559:20)
flovilmart commented 5 years ago

Can you try with the latest version of parse-server and mongodb with version 3.x not 4.x?

mrmarcsmith commented 5 years ago

We have a significant overhaul to be ready for parse-server 3.x and downgrading mongo is pretty high risk for a sharded production cluster. In the mean time we just hot fixed the way the query was constructed to avoid a relational query and moved to a whole new cluster. I'll do some testing tomorrow and let you know if the new cluster stops the error.

flovilmart commented 5 years ago

So how was this issue discovered?

flovilmart commented 5 years ago

As a side question, what is the necessity for sharding?

mrmarcsmith commented 5 years ago

we have a lesser used administrative feature that executed the query. because of the non-critical nature of this feature it isn't covered by tests.

Sharding allows for a unified database that enforces sending requests to "shards" that reside in the same region as the user. for a New York user, why send a request from California to New York when you could access the New York servers directly.

flovilmart commented 5 years ago

So what’s going on is likely the roles not being discoverable because of your usage of sharding. Not sure how to fix nor provide a proper reproduction step.

mrmarcsmith commented 5 years ago

@flovilmart I discovered the issue here. TL;DR We load balance our mongos servers behind a Kubernetes "service" but apparently mongos instances require session affinity. I'm looking for a solution now, I'll post what we find incase anyone else stumbles across the same issue.

mrmarcsmith commented 5 years ago

For future searchers, Per Mongo documentation each application servers should have it's own "mongos" instance. For us that looked like colocating a Parse Server and a Mongos in the same pod.