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https://issues.apache.org/jira/browse/HDFS-15751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17254662#comment-17254662
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Konstantin Shvachko commented on HDFS-15751:
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Added documentation for {{msync()}}.
I put a reference to HDFS documentation describing [Consistent Reads from
Observer|https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-hdfs/ObserverNameNode.html]
particulalrly the semantics of {{msync()}} in HDFS. Otherwise it is hard to
define it in abstract terms without the context.
I was also thinking about {{AbstractContract}}* type tests for {{msync}} but
could not think of anything valuable that can be tested here. Essentially we
need call {{mkdir()}} and then verify that after {{msync}} the metadata exists
via a read call, which we do for HDFS in {{TestConsistentReadsObserver}}. But
it is a probabilistic thing as it can succeed even without synchronization if
standby catches up fast enough. I guess testing consistency contracts is
similar to atomicity, which we don't test in {{AbstractContract}} tests, since
it not clear how.
> Add documentation for msync() API to filesystem.md
> --------------------------------------------------
>
> Key: HDFS-15751
> URL: https://issues.apache.org/jira/browse/HDFS-15751
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: documentation
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Priority: Major
> Attachments: HDFS-15751-01.patch
>
>
> HDFS-15567 introduced new {{FileSystem}} call {{msync()}}. Should add it to
> the API definitions.
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