Unable to use MongoDB Change Streams. MongoError: The $changeStream stage is only supported on replica sets

11017

I am trying to use Mongo Change Streams to listen for changes in a collection. Following is my code.

const collection = cmt.collection('foo');
    const changeStream = collection.watch();
    changeStream.on('change', async (next) => {
        if(next && next.fullDocument){
            let row = next.fullDocument;
            console.log('event', row);
            // dealing with row
    }
});

But while registering, I am getting the following error

/Users/experimental/githome/foo/node_modules/mongodb/lib/utils.js:132
      throw err;
      ^

MongoError: The $changeStream stage is only supported on replica sets
    at Connection.<anonymous> (/Users/experimental/githome/foo/node_modules/mongodb-core/lib/connection/pool.js:443:61)
    at Connection.emit (events.js:182:13)
    at processMessage (/Users/experimental/githome/foo/node_modules/mongodb-core/lib/connection/connection.js:364:10)
    at Socket.<anonymous> (/Users/experimental/githome/foo/node_modules/mongodb-core/lib/connection/connection.js:533:15)
    at Socket.emit (events.js:182:13)
    at addChunk (_stream_readable.js:283:12)
    at readableAddChunk (_stream_readable.js:264:11)
    at Socket.Readable.push (_stream_readable.js:219:10)
    at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)
Emitted 'error' event at:
    at processNewChange (/Users/experimental/githome/foo/node_modules/mongodb/lib/change_stream.js:436:43)
    at Cursor.<anonymous> (/Users/experimental/githome/foo/node_modules/mongodb/lib/change_stream.js:272:5)
    at Cursor.emit (events.js:182:13)
    at next (/Users/experimental/githome/foo/node_modules/mongodb/lib/cursor.js:1018:14)
    at err (/Users/experimental/githome/foo/node_modules/mongodb/lib/utils.js:411:14)
    at executeCallback (/Users/experimental/githome/foo/node_modules/mongodb/lib/utils.js:401:25)
    at handleCallback (/Users/experimental/githome/foo/node_modules/mongodb/lib/utils.js:128:55)
    at cursor._next (/Users/experimental/githome/foo/node_modules/mongodb/lib/operations/cursor_ops.js:194:21)
    at queryCallback (/Users/experimental/githome/foo/node_modules/mongodb-core/lib/cursor.js:662:23)
    at /Users/experimental/githome/foo/node_modules/mongodb-core/lib/connection/pool.js:397:18
    at process._tickCallback (internal/process/next_tick.js:61:11)

What is the issue with my code/ setup?

1 Answer

5 years ago by

MongoDB chain streams option is available in replica sets setup only, but not in a standalone installation. However, you can update your standalone installation to a single node replica set by following the below steps.

1. Locate the mongodb.conf file and add the replica set details

Add the following replica set details to mongodb.conf file

replication:
  replSetName: "<replica-set name>"

Example:

replication:
  replSetName: "rs0"

Note: Location in brew installed MongoDB /usr/local/etc/mongod.conf

2. Initiate the replica set using rs.initiate()

Login to MongoDB shell and run the command rs.initiate() this will start your replica set. Logs looks like following on successful start

> rs.initiate()
{
	"info2" : "no configuration specified. Using a default configuration for the set",
	"me" : "127.0.0.1:27017",
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1577545731, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1577545731, 1)
}

Reference: https://onecompiler.com/posts/3vchuyxuh/enabling-replica-set-in-mongodb-with-just-one-node

5 years ago by Karthik Divi