$by_category projection issue


We are having a trouble with $by_category projection. The issue is that category that we are reading has no events that exist in original stream.

Here are the contents of a category: http://i.imgur.com/Yb70m33.png. There is event # 10, and then right after it event #13 from the same stream.

If I open stream itself: http://i.imgur.com/SNEHY5D.png, events are in the right order and go one after another as expected.

If I go to projections list and reset $by_category, events are appearing in the right order. I don’t really know the reason why such thing happen. What can I check to find out?


Was there some kind of failure condition (e.g. a master takeover in a cluster) around the time this happened? I’ve not previously seen this, but it would be explained by a bug in recovering from a checkpoint (which is also causing other problems right now)

We are running a single node. Unfortunately we can’t have stable reproduce steps.

For the same DB while starting we have error message

[08084,16,11:36:34.905] The ‘$by_category’ projection faulted due to ‘An event emitted in recovery differ from the originally emitted event. Existing(’$>’, ‘C:49098978/P:49098467’). New(’$>’, ‘C:49098284/P:49097159’)’

But after projection restart issue it builds. We didn’t upgrade versions and always were running 3.0.1. Could this be related?

Yes, that sounds related.

Are you able to supply us with a copy of your database for further analysis?



I thought the issue was resolved by rerunning…