Summary

We got a Mongomirror help ticket that complains Mongomirror didn't migrate all the collections from a 2.6 replicaset. After debugging I found the cursor returned from Go drive ListCollections function doesn't return all the collections during iteration. There are at most 101 collections returned by the cursor.

This happens on 2.6 server either standalone or replicaset.

How to Reproduce

Use mlaunch to bring up a 2.6 server on port 27017. Run main.go.

You will see although 120 collections were created, the output is 

...

col97
col98
col99
count: 101, cursor err: <nil>