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https://issues.apache.org/jira/browse/HBASE-20952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16568906#comment-16568906
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Zach York commented on HBASE-20952:
-----------------------------------
So taking a very rough stab at this based on a few thoughts, but at the most
basic level, what functionality do we need from the WAL?
Absolutely Necessary:
append/put/write/etc
getEditsForRegion(Region) - This let's the implementation handle the mess -
WALSplitter, multi-wal, etc
Probably some sort of delete of edits before a threshold
Nice to have:
onRegionFlush() - This would be kinda like a coprocessor hook which could add
implementation specific logic (rolling file logs, adding some sort of
lastFlushed functionality, or any of the things that [~stack] was talking about
in his comment)
In general, I would like to start from what we truly need, not what we
currently have :) . I don't want the interface polluted by implementation
specific methods. I'm sure I'm over simplifying things, but I wanted to get the
conversation started.
> Re-visit the WAL API
> --------------------
>
> Key: HBASE-20952
> URL: https://issues.apache.org/jira/browse/HBASE-20952
> Project: HBase
> Issue Type: Sub-task
> Components: wal
> Reporter: Josh Elser
> Priority: Major
>
> Take a step back from the current WAL implementations and think about what an
> HBase WAL API should look like. What are the primitive calls that we require
> to guarantee durability of writes with a high degree of performance?
> The API needs to take the current implementations into consideration. We
> should also have a mind for what is happening in the Ratis LogService (but
> the LogService should not dictate what HBase's WAL API looks like RATIS-272).
> Other "systems" inside of HBase that use WALs are replication and
> backup&restore. Replication has the use-case for "tail"'ing the WAL which we
> should provide via our new API. B&R doesn't do anything fancy (IIRC). We
> should make sure all consumers are generally going to be OK with the API we
> create.
> The API may be "OK" (or OK in a part). We need to also consider other methods
> which were "bolted" on such as {{AbstractFSWAL}} and
> {{WALFileLengthProvider}}. Other corners of "WAL use" (like the
> {{WALSplitter}} should also be looked at to use WAL-APIs only).
> We also need to make sure that adequate interface audience and stability
> annotations are chosen.
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