Handle migrations ourselves (NOT through mongokit)

[Christopher Allan Webber]

Mongokit's migrations system stuff is complex and way confusing. Here's something much simpler.

• migrations are simple functions, iterated by number. You create them and register them with a decorator registering what "number" they are like so:

  @register_migration(1) def ponies_to_unicorns(database): database['quadrapeds'].find( {'animal': 'pony'}).update{ {'$set': {'animal': 'unicorn'}})

or whatever else you need to do with that connection. The first and only argument passed in (database) is a simple pymongo database connection (not mongokit!). Otherwise, it's just a simple python function. Do what you need to do.

• current migration status is stored in the ['_id'] = 'mediagoblin' document of database['app_metadata'] in the field ['migration_number']
• if no migrations have been run yet, migration_number set to current max
• otherwise all unrun migrations are run, and migration_number updated after each migration finishes.

[Christopher Allan Webber]

New migrations are ready for merge! It includes really good tests, so I'm pretty confident that it really is ready!

[https://gitorious.org/_{cwebber/mediagoblin/cwebbers-mediagoblin/commits/f411_new_migrations](https://gitorious.org/}cwebber/mediagoblin/cwebbers-mediagoblin/commits/f411_new_migrations)

Honestly, the reason I haven't merged it is once we dump a migration into here is that the first migration might not apply for reasons that are confusing to describe. I'll write a nice script to handle that and post it with an announcement to the list tomorrow once I do the proper merge. Then I'll write the first merge:

http://bugs.foocorp.net/issues/372

should be pretty simple!

[Christopher Allan Webber]

This is finally done and even pushed live. If you have an old database, you might need to run a script... see the mailing list.

Everything works though, yay!

[Christopher Allan Webber]

newmigration_fix.py

[Christopher Allan Webber]

Here's the relevant script in case you care. Run like:

./bin/python newmigration_fix.py

[Will Kahn-Greene]

The original url for this bug was ​http://bugs.foocorp.net/issues/411 .
Relations:
#111: blocks, #86: blocks