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From "Aaron Fabbri (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13761) S3Guard: implement retries for DDB failures and throttling; translate exceptions
Date Thu, 11 Jan 2018 03:37:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16321643#comment-16321643
] 

Aaron Fabbri commented on HADOOP-13761:
---------------------------------------

Reminder comment here: We should also:

- Update MetadataStore javadoc to say that implementations *must* implement their own retries
as needed to recover from transient issues like services unavailable or network connectivity
blips. (The most sane design decision IMO.. especially if more backends are added in the future).

- Update any S3Guard-specific retry annotations in S3A FS to assume MetadataStores do their
own retries.  e.g. the {{Retries.OnceTranslated("s3guard not retrying")}} being added to listLocatedStatus()
in HADOOP-15079.

> S3Guard: implement retries for DDB failures and throttling; translate exceptions
> --------------------------------------------------------------------------------
>
>                 Key: HADOOP-13761
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13761
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 3.0.0-beta1
>            Reporter: Aaron Fabbri
>            Assignee: Steve Loughran
>            Priority: Blocker
>
> Following the S3AFileSystem integration patch in HADOOP-13651, we need to add retry logic.
> In HADOOP-13651, I added TODO comments in most of the places retry loops are needed,
including:
> - open(path).  If MetadataStore reflects recent create/move of file path, but we fail
to read it from S3, retry.
> - delete(path).  If deleteObject() on S3 fails, but MetadataStore shows the file exists,
retry.
> - rename(src,dest).  If source path is not visible in S3 yet, retry.
> - listFiles(). Skip for now. Not currently implemented in S3Guard. I will create a separate
JIRA for this as it will likely require interface changes (i.e. prefix or subtree scan).
> We may miss some cases initially and we should do failure injection testing to make sure
we're covered.  Failure injection tests can be a separate JIRA to make this easier to review.
> We also need basic configuration parameters around retry policy.  There should be a way
to specify maximum retry duration, as some applications would prefer to receive an error eventually,
than waiting indefinitely.  We should also be keeping statistics when inconsistency is detected
and we enter a retry loop.



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