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stack commented on HBASE-20952: ------------------------------- Reading doc. (comments nor copy/paste allowed -- please fix... add reference here and author), the study of other logging systems resulted in "...no significant influence on HBase WAL API design." though above Josh says " I can say that a significant portion of the direction was strongly influenced by Apache DistributedLog". Then we have a listing of the classes involved writing the WAL with stuff like this: {{WAL implements WALFileLengthProvider}} Nothing on "What was the reasoning behind this API?"[Josh] or what it is -- its the WAL we have already? (Why even have a WALFileLengthProvider and not just add a length method on the WAL Interface? Does Replication just need lengths to work? If so, discussion?). Then comes 'design considerations'. #1 is not a design consideration but a note that code has been refactored. #2 is that we should be able to choose WAL via Configuration. #3 is an aspirational, abstract classes should not be tied to fs implementation, and #4 is a note on WAL metadata capability, a concept first mentioned here but unexplained/justified till later. I see no discussion of 'region' entity in here. > 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 > Attachments: 20952.v1.txt > > > 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. -- This message was sent by Atlassian JIRA (v7.6.3#76005)