Send database reads to a slave handle for scaling purposes
An option for a slave handle would be beneficial for scaling. We could send all reads that aren't sensitive to replication lag to this handle and gain quite a bit of room to scale on our write masters. Besides just having the handle, we also need a nice way for devs to indicate that a query is safe to execute on a slave. We could probably indicate the "safeness" in context. In the db api we can indicate safeness using a decorator.
Blueprint information
- Status:
- Complete
- Approver:
- Russell Bryant
- Priority:
- High
- Drafter:
- Michael H Wilson
- Direction:
- Approved
- Assignee:
- Michael H Wilson
- Definition:
- Approved
- Series goal:
- Accepted for havana
- Implementation:
-
Implemented
- Milestone target:
-
2013.2
- Started by
- Russell Bryant
- Completed by
- Michael H Wilson
Related branches
Related bugs
Sprints
Whiteboard
Gerrit topic: https:/
Addressed by: https:/
Add lag_tolerant flag to Context class.
Addressed by: https:/
Add _safe_for_slave decorator to sqlalchemy db api.
I think there's enough feedback from people to safely say that the decorator + context approach isn't going to fly. As such, I'm going to move that portion of things into the implementation of "slaveifying" various code paths. Essentially, without these two things this blueprint is done.
Work Items
Work items:
Slave handle into oslo-incubator and synced to nova: DONE
Dependency tree
* Blueprints in grey have been implemented.
