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https://issues.apache.org/jira/browse/AURORA-112?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joe Smith updated AURORA-112:
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Labels: O3 (was: )
> Introduce formalized schema migrations into the scheduler
> ---------------------------------------------------------
>
> Key: AURORA-112
> URL: https://issues.apache.org/jira/browse/AURORA-112
> Project: Aurora
> Issue Type: Story
> Components: Scheduler
> Reporter: Kevin Sweeney
> Labels: O3
>
> Right now a change in the schema for persisted Thrift structs is handled by a
> rather large "backfill" method that translates from the old schema to the new
> one. This is a potential source of datastore corruption bugs.
> Some thoughts on the overall design of this "backfill" mechanism. The first
> is that any structs we persist should have a SCHEMA_VERSION or some such
> identifier that gets incremented on subsequent version changes (we could use
> also use heuristics here but I think a monotonically increasing version
> number is cleaner). The second is that we should define, essentially, a state
> machine that takes a V1 struct to a V2 struct (and potentially provides an
> inverse operation, but that's not necessary). Basically a piece of code that
> knows how to make a valid V1 struct a valid V2 struct. Part of any schema
> change will be adding this code, and in this way we will be able to load
> arbitrarily old persisted structs while keeping the code to do so relatively
> clean (each "backfill migration" is a tiny piece of code).
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