Mongomirror unable to see collections on source DB

Sorry for the bad formatting!

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 can’t find any documentation on this error. I’ve followed the instructions listed on this page

Source version of MongoDB= 2.6.4
ReplicaSet= true
Operating System= Red Hat Enterprise Linux Server 7.9
Node Count= 1
Data Size= 400gb

  "user" : "admin",
        "db" : "admin",
        "roles" : [
                        "role" : "clusterAdmin",
                        "db" : "admin"
                        "role" : "readWriteAnyDatabase",
                        "db" : "admin"
                        "role" : "readAnyDatabase",
                        "db" : "admin"
                        "role" : "backup",
                        "db" : "admin"

Any insight is greatly appreciated!

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’m sure it would also be helpful to see my command

/path/to/mongomirror-linux-x86_64-rhel70-0.12.8/bin/mongomirror \
 --host=<replicaSetName/host:port>  \
 --username=admin \
 --password=<password> \
 --authenticationDatabase=admin \
 --authenticationMechanism=MONGODB-CR \
 --destination=<replicaSetName/host:port> \
 --destinationUsername=admin \
 --includeNamespace=<DB>.<very small Collection> \
 --noTLS \
 --tlsInsecure \
 > /path/to/mongomirror.log

Updating this as I was able to solve my problem. There was a typo in one of my IP adresses…

Anyway their is a new problem:

2023-04-17T14:55:39.419-0400    Attempting initial sync from: host:27017
2023-04-17T14:55:39.428-0400    Collection `REDACTED` was not found on the source. Skipping initial sync.

And this happens for numerous collections

It sounds like this is on-prem to on-prem restoring of data, mongomirror is used for transferring a MongoDB replica set to an Atlas Replica set.

If you are looking to backup / restore your data on prem you should use mongoimport and mongodump.

You’re correct about on-prem to on-prem. But What’s really the difference between Atlas and an on-prem db? They are running the same underlying code.

Even if I was migrating to Atlas, this problem has more to do with the source data than with the destination.

Mongomirror was recommended to us by multiple mongoDB consultants. I think the documentation is lacking on capabilities.

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.

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