[jira] [Commented] (NIFI-4715) ListS3 produces duplicates in frequently updated buckets

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NIFI-4715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16302649#comment-16302649 ] 

ASF GitHub Bot commented on NIFI-4715:
--------------------------------------

GitHub user adamlamar opened a pull request:

    https://github.com/apache/nifi/pull/2361

    NIFI-4715: ListS3 produces duplicates in frequently updated buckets

    Thank you for submitting a contribution to Apache NiFi.
    
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You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/adamlamar/nifi NIFI-4715

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/nifi/pull/2361.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #2361
    
----
commit bcaa84bba251c3a70c27a466185f6b20863eab93
Author: Adam Lamar <ad...@...>
Date:   2017-12-24T03:29:02Z

    NIFI-4715: ListS3 produces duplicates in frequently updated buckets

----


> ListS3 produces duplicates in frequently updated buckets
> --------------------------------------------------------
>
>                 Key: NIFI-4715
>                 URL: https://issues.apache.org/jira/browse/NIFI-4715
>             Project: Apache NiFi
>          Issue Type: Bug
>          Components: Core Framework
>    Affects Versions: 1.2.0, 1.3.0, 1.4.0
>         Environment: All
>            Reporter: Milan Das
>         Attachments: List-S3-dup-issue.xml, screenshot-1.png
>
>
> ListS3 state is implemented using HashSet. HashSet is not thread safe. When ListS3 operates in multi threaded mode, sometimes it  tries to list  same file from S3 bucket.  Seems like HashSet data is getting corrupted.
> currentKeys = new HashSet<>(); // need to be implemented Thread Safe like currentKeys = //ConcurrentHashMap.newKeySet();
> *{color:red}+Update+{color}*:
> This is not a HashSet issue:
> Root cause is: 
> When the file gets uploaded to S3 simultaneously  when List S3 is in progress.
> onTrigger-->  maxTimestamp is initiated as 0L.
> This is clearing keys as per the code below
> When lastModifiedTime on S3 object is same as currentTimestamp for the listed key it should be skipped. As the key is cleared, it is loading the same file again. 
> I think fix should be to initiate the maxTimestamp with currentTimestamp not 0L.
> {code}
>  long maxTimestamp = currentTimestamp;
> {code}
> Following block is clearing keys.
> {code:title=org.apache.nifi.processors.aws.s3.ListS3.java|borderStyle=solid}
>  if (lastModified > maxTimestamp) {
>                     maxTimestamp = lastModified;
>                     currentKeys.clear();
>                     getLogger().debug("clearing keys");
>                 }
> {code}



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