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https://issues.apache.org/jira/browse/HDFS-3731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13434576#comment-13434576
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Colin Patrick McCabe commented on HDFS-3731:
--------------------------------------------
The design doc for HDFS-265 says:
bq. RWR (Replica Waiting to be Recovered): If a DataNode dies and restarts, all
its rbw replicas change to be in the rwr state. Rwr replicas will not be in
any pipeline and therefore will not receive any new bytes. They will either
become out of date or will participate in a lease recovery if the client also
dies.
It seems to me that by putting the blocks into the rbw directory, what will
happen when the 2.x DataNode is started is that the blocks will participate in
lease recovery after a few minutes have gone past.
There is a unit test in this patch which short-cuts this process by manually
invoking lease recovery on the files and then verifying that they can be read.
Is there any more documentation about the lease recovery process? As far as I
can tell, it seems to work fine on the files in this patch. It might be useful
to test waiting for automatic lease recovery to be triggered rather than
invoking it manually.
> 2.0 release upgrade must handle blocks being written from 1.0
> -------------------------------------------------------------
>
> Key: HDFS-3731
> URL: https://issues.apache.org/jira/browse/HDFS-3731
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node
> Affects Versions: 2.0.0-alpha
> Reporter: Suresh Srinivas
> Assignee: Colin Patrick McCabe
> Priority: Blocker
> Attachments: HDFS-3731.002.patch, HDFS-3731.003.patch
>
>
> Release 2.0 upgrades must handle blocks being written to (bbw) files from 1.0
> release. Problem reported by Brahma Reddy.
> The {{DataNode}} will only have one block pool after upgrading from a 1.x
> release. (This is because in the 1.x releases, there were no block pools--
> or equivalently, everything was in the same block pool). During the upgrade,
> we should hardlink the block files from the {{blocksBeingWritten}} directory
> into the {{rbw}} directory of this block pool. Similarly, on {{-finalize}},
> we should delete the {{blocksBeingWritten}} directory.
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