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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13826) S3A Deadlock in multipart copy due to thread pool limits.
Date Fri, 02 Dec 2016 17:37:58 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15715769#comment-15715769
] 

Steve Loughran commented on HADOOP-13826:
-----------------------------------------

one thing to consider: now that we've gone to fast upload streams each with their own bounded
queues, does the main queue need to be bounded at all? I guess we have to limit it by the
size of the active connections.

we know the big ones are PUT, PUT-PART, COPY and COPY-PART right? The puts are limited per
stream; if that is locked down (todo: check those numbers), then there's no overload on memory
unless there are many streams trying to write simultaneously.

Copy could get the same treatment: we will need to throttle the number of active copy request
across the entire FS. Which means the parallel renaming should share a blocking pool with
all other threads trying to do copies

Oh, and I'd like to submit async delete and simple zero-byte put operations somewhere, alongside
any async parent directory check (goal: do the full parent treewalk on create(), but async
and only validate the results before that first PUT). 

> S3A Deadlock in multipart copy due to thread pool limits.
> ---------------------------------------------------------
>
>                 Key: HADOOP-13826
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13826
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs/s3
>    Affects Versions: 2.7.3
>            Reporter: Sean Mackrory
>            Assignee: Sean Mackrory
>            Priority: Critical
>         Attachments: HADOOP-13826.001.patch, HADOOP-13826.002.patch
>
>
> In testing HIVE-15093 we have encountered deadlocks in the s3a connector. The TransferManager
javadocs (http://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/transfer/TransferManager.html)
explain how this is possible:
> {quote}It is not recommended to use a single threaded executor or a thread pool with
a bounded work queue as control tasks may submit subtasks that can't complete until all sub
tasks complete. Using an incorrectly configured thread pool may cause a deadlock (I.E. the
work queue is filled with control tasks that can't finish until subtasks complete but subtasks
can't execute because the queue is filled).{quote}



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