[jira] [Updated] (FLINK-6383) Add versioning for AbstractStreamOperator state

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-6383?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aljoscha Krettek updated FLINK-6383:
------------------------------------
    Priority: Major  (was: Blocker)

> Add versioning for AbstractStreamOperator state
> -----------------------------------------------
>
>                 Key: FLINK-6383
>                 URL: https://issues.apache.org/jira/browse/FLINK-6383
>             Project: Flink
>          Issue Type: Improvement
>          Components: DataStream API
>    Affects Versions: 1.3.0
>            Reporter: Aljoscha Krettek
>            Assignee: Aljoscha Krettek
>             Fix For: 1.3.0
>
>
> Right now, {{AbstractStreamOperator}} checkpoints key-group state in {{AbstractStreamOperator.snapshotState(StateSnapshotContext context)}}. Currently, this is the timers for each key group. We might want to change the format of this or what we store in the future. In order to facilitate this we should write a version to the beginning of the stream so that we can deal with schema updates.
> For dealing with the fact that we don't currently write a version number we have to at a magic number add the beginning (think {{0xCAFEBABE}}). For dealing with state that was written prior to versioning we read the first 8 bytes, buffer them, if they match the magic number we read the version and from then on jump to the logic based on the version. If the magic number doesn't match we know we have state from a pre-version version and read the stream using the old code, including the 8 buffered bytes.



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