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https://issues.apache.org/jira/browse/HDDS-14355?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Attila Doroszlai resolved HDDS-14355.
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Fix Version/s: 2.2.0
Resolution: Implemented
> Allow createKey to skip allocateBlock for empty key
> ---------------------------------------------------
>
> Key: HDDS-14355
> URL: https://issues.apache.org/jira/browse/HDDS-14355
> Project: Apache Ozone
> Issue Type: Improvement
> Reporter: Ivan Andika
> Assignee: Ivan Andika
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.2.0
>
>
> Currently, it seems that OMKeyRequest#allocateBlock calls SCM's allocateBlock
> RPC even if the requested size is 0, we can skip this call for createKey to
> save redundant SCM calls.
> This might be useful if we only want to test the write OM metadata
> performance without involving HDDS layer (i.e. SCM and DN). Additionally, S3
> users might also benefit from this since from S3G logs, there are quite a
> number of requests with 0 requested data size.
> Note that OFS / O3FS always use a dataSize = 0 (since FS users do not know
> how much data is going to be uploaded). For that reason, {{createFile}} will
> not enable the feature. Note: since {{OmKeyArgs.dataSize}} is optional, it
> should be more appropriate to not specify the data size if we don't know
> final data size of the key. This would make the API simpler, but since
> {{dataSize}} seems to always be sent in {{{}createFile{}}}, we have to work
> around this.
> Test should validate that SCM allocateBlock should never be called when
> uploading a zero-sized key (either by OMKeyCreateRequest or
> OMAllocateBlockRequest (from the
> BlockOutputStreamEntryPool#allocateNewBlock)).
> This might be useful if we only want to test the write OM metadata
> performance without involving HDDS layer (i.e. SCM and DN). Additionally, we
> have seen some users using empty keys to implement distributed locking on top
> of Ozone due to its strong consistency.
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