Mongodb charm should support persistent storage

[Tom Haddon]

Currently the mongodb charm doesn't support persistent storage. We should fix that. The PostgreSQL charm is an example of how this could be implemented.

[Richard Harding (rharding)]

The charm does support persistent storage in a basic sense. You can specify the location to store data. The issue is that there's a bug in the mounting of volumes. The command doesn't obey the specified mount point location and it needs to be 'guessed' by the charm which is why the fix to auto mount wasn't accepted into the charm. We can use persistent storage, we just need to adjust the deploy steps to manually attach the volume to the instance and then to change the mongodb config to point the data store to a location on that volume.

Bug for reference:
https://bugs.launchpad.net/nova/+bug/1088430

[Tom Haddon (mthaddon)]

Specifying a location for data to be stored is not the same as supporting persistent storage. Please see the PostgreSQL charm for an example of what needs implementing.

[Curtis Hovey (sinzui)]

Isn't this bug, the intention, identical to bug 1170661? I have a branch that attempts to fix that bug. There is a fault that I have not had time to resolve though.

[Tom Haddon (mthaddon)]

I don't think so, Curtis - that bug seems to be about restoring from a dumpfile. I had thought there was already a bug about persistent storage but couldn't find it, so I filed this one. I did see that there was a branch of yours already about it, wanted to file this bug so we can track it on an ongoing basis. Thanks!

[Curtis Hovey (sinzui)]

This bug is a duplicate of Bug #1130764: db and data are not persistence, reported against charmworld several months ago. out proposed fix was rejected.