72007: LiveSync connector failed to track its position

A LiveSync MongoDB connector could not save its change-stream resume token to the database. The token records how far the connector has read, so that it can continue from the same point after a restart.

What you should do

Grant the connector's database user permission to read and write the ably collection, where the resume token is stored as a document. Without write access there, the connector cannot record how far it has read.

Why it happens

The MongoDB connector saves its change-stream resume token to a document in a collection named ably, and it could not write it. This is usually because the connection's database user lacks read and write permission on that collection.

What you'll see

The error is reported with code 72007 and HTTP status 500. The message is of the form unable to store resume token: <detail>.