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https://issues.apache.org/jira/browse/HDFS-12178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16098989#comment-16098989
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Nandakumar commented on HDFS-12178:
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Thanks [~vagarychen] for the review.
> Curious though, is there a case where multiple threads will try to create the
> same container?
Since we are not checking {{keyInfo.getShouldCreateContainer()}} for container
creation, all {{createKey}} call will try to create container (if not in local
cache {{containersCreated}}). And tools like Corona will start multiple threads
to put data into ozone, in such scenarios multiple threads will try to create
same container.
> createContainer can fail, but it already gets added to containersCreated set
> to this point
It is assumed that {{ContainerProtocolCalls.createContainer(xceiverClient,
requestId)}} call will fail most of the time, since we will be trying to create
an already existing container.
If we switch the order of those two statements, we will never be adding
containerName to the cache since there will always be exception thrown during
createContainer call (in case of existing container), and all the {{createKey}}
call will always try to create container which is same as not having
{{containersCreated}} cache.
>or simply move containersCreated.add() to after the try-catch?
This will work, but it doesn't make much of a difference, whether we have it as
first statement in try or move it totally outside of try-catch block. Both will
behave the same way.
> Ozone: OzoneClient: Handling SCM container creationFlag at client side
> ----------------------------------------------------------------------
>
> Key: HDFS-12178
> URL: https://issues.apache.org/jira/browse/HDFS-12178
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ozone
> Reporter: Nandakumar
> Assignee: Nandakumar
> Attachments: HDFS-12178-HDFS-7240.000.patch,
> HDFS-12178-HDFS-7240.001.patch
>
>
> SCM BlockManager provisions a pool of containers upon block creation request,
> only one container is returned with creationFlag to the client. The other
> containers provisioned in the same batch will not have this flag. This jira
> is to handle that scenario at client side, until HDFS-11888 is fixed.
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