Info
In order to work correctly, the merging logic on mongos needs to know that a cursor is tailable. An aggregation with a $changeNotification is tailable, but doesn't communicate that information, so the merging logic mistakenly hangs, repeatedly asking for the next document, since the cursor id is never set to 0.
Top User Comments
xgen-internal-githook commented on Wed, 26 Jul 2017 22:05:08 +0000:
Author:
{'email': 'charlie.swanson@mongodb.com', 'username': 'cswanson310', 'name': 'Charlie Swanson'}
Message: SERVER-30246 Error if $changeNotification is sent to mongos.
Branch: master
https://github.com/mongodb/mongo/commit/7d9038a90fffa22b58323df1a5221aa9b30f853c
Steps to Reproduce
Run an aggregate with a $changeNotification stage on a mongos (shards must be replica sets)
