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From "Virajith Jalaparti (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9809) Abstract implementation-specific details from the datanode
Date Mon, 11 Jul 2016 19:14:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15371440#comment-15371440

Virajith Jalaparti commented on HDFS-9809:

Hi [~eddyxu],

Thank you for the comments! Replies below. 

bq. {{BlockSender#waitForMinLength}}, it is not clear to me that why you need to change {{RBW}}
to {{RIP}} ?

This should have actually been {{ReplicaInPipelineInterface}} instead of {{ReplicaInPipeline}}.
The idea in replacing this was: when we add a {{ProvidedReplica}} as part of HDFS-9806, the
{{ProvidedReplica}} would be implementing {{ReplicaInPipelineInterface}} so that it can tie
into the existing replication pipeline in the datanode. So, if references to {{ReplicaInPipeline}}
and {{ReplicaBeingWritten}} are replaced by {{ReplicaInPipelineInterface}}, parts of the current
code can be used for both {{LocalReplica}} and {{ProvidedReplica}}. The current patch does
not have these replacements as implementing writes for {{ProvidedReplica}} was future work
of HDFS-9806 and not in its scope. I understand that this should not preclude replacement
by {{ReplicaInPipelineInterface}} as it would eventually be needed. I will make these modifications
and post a new patch soon. 

bq. {{DataStorage#getTrashDirectoryForBlockFile}} we can take this chance to rename it to
{{getTrashDirectoryForBlock}} or {{..ForReplica}}.

Agreed. Will do. 

bq. There are many {{UnsupportedOperationException}} in Replica class hierarchy. It might
indicates that these functions are not supposed to be override.

As some of the functions were moved up from the Replica class hierarchy (e.g., RIP etc. to
{{ReplicaInfo}}) and other sub-classes of {{ReplicaInfo}} may not implement it, these were
declared to throw {{UnsupportedOperationException}}. I agree that this is not necessary as
it is a {{RuntimeException}}. I will update the patch without the {{UnsupportedOperationException}}.

bq. ASF License for every new file.

Will add it. 

bq. Lets take this chance to use JDK 7 {{try..resource}} in {{breakHardlilnks()}} ?

Sure. Will change to use {{try..resource}}. 

bq. {{ReplicaInPipeline#moveReplicaFrom}} it still has a {{File}} parameter.

Yes, this needs to be removed. This will be part of the changes to be made following the first
point above. 

> Abstract implementation-specific details from the datanode
> ----------------------------------------------------------
>                 Key: HDFS-9809
>                 URL: https://issues.apache.org/jira/browse/HDFS-9809
>             Project: Hadoop HDFS
>          Issue Type: Task
>          Components: datanode, fs
>            Reporter: Virajith Jalaparti
>            Assignee: Virajith Jalaparti
>         Attachments: HDFS-9809.001.patch, HDFS-9809.002.patch, HDFS-9809.003.patch
> Multiple parts of the Datanode (FsVolumeSpi, ReplicaInfo, FSVolumeImpl etc.) implicitly
assume that blocks are stored in java.io.File(s) and that volumes are divided into directories.
We propose to abstract these details, which would help in supporting other storages. 

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