We are trying to migrate off MongoDB 2.6 to MongoDB 4.2 (eventually to 5.0, but not yet). I am running the latest version of mongomirror to copy the data to the new instance. However, I keep running into the same error: Failed: could not get collections names from the source: EOF
I would also like to add that I have successfully used the tool to migrate data from a brand new 2.6.4 db to a 4.2 db. I was testing the tool and validating that the config would work as expected. so the versions of the source DB shouldn’t be a problem, right?
I was just informed the problem is with mongomirror.
Turns out there is an reported issue with MongoDB Server version 2.6 with Go Driver which is used in MongoMirror. This issue specifically arises when there are more than 100 collections. I’m not able to verify this but this seems to be likely explanation.