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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15541) AWS SDK can mistake stream timeouts for EOF and throw SdkClientExceptions
Date Tue, 19 Jun 2018 18:42:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16517417#comment-16517417

Steve Loughran commented on HADOOP-15541:

Stream draining means the http1.1 connection can be returned to the pool and so save setup
costs, which is why we like to do it on close()

But here, if we can conclude that the connection is in trouble, should we return it it? 

No objection to doing the abort for IOEs and SDKs, I was suggesting the arg because the reopen
code already takes that param...requesting that forced abort after an exception on read()
would be good.

though: are you suggesting for any IOE/SDK exception we don't try to reopen the call, just
force the abort() before throwing up the exception? If so, yes, that also makes sense. We
don't want a failing HTTP connection to be recycled

Make sure any metrics on forced aborts are incremented though

> AWS SDK can mistake stream timeouts for EOF and throw SdkClientExceptions
> -------------------------------------------------------------------------
>                 Key: HADOOP-15541
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15541
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs/s3
>    Affects Versions: 2.9.1, 2.8.4, 3.0.2, 3.1.1
>            Reporter: Sean Mackrory
>            Assignee: Sean Mackrory
>            Priority: Major
> I've gotten a few reports of read timeouts not being handled properly in some Impala
workloads. What happens is the following sequence of events (credit to Sailesh Mukil for figuring
this out):
>  * S3AInputStream.read() gets a SocketTimeoutException when it calls wrappedStream.read()
>  * This is handled by onReadFailure -> reopen -> closeStream. When we try to drain
the stream, SdkFilterInputStream.read() in the AWS SDK fails because of checkLength. The underlying
Apache Commons stream returns -1 in the case of a timeout, and EOF.
>  * The SDK assumes the -1 signifies an EOF, so assumes the bytes read must equal expected
bytes, and because they don't (because it's a timeout and not an EOF) it throws an SdkClientException.
> This is tricky to test for without a ton of mocking of AWS SDK internals, because you
have to get into this conflicting state where the SDK has only read a subset of the expected
bytes and gets a -1.
> closeStream will abort the stream in the event of an IOException when draining. We could
simply also abort in the event of an SdkClientException. I'm testing that this results in
correct functionality in the workloads that seem to hit these timeouts a lot, but all the
s3a tests continue to work with that change. I'm going to open an issue with the AWS SDK Github
as well, but I'm not sure what the ideal outcome would be unless there's a good way to distinguish
between a stream that has timed out and a stream that read all the data without huge rewrites.

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