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Date: Tue, 18 May 2010 01:46:56 -0400 (EDT)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-1142) Lease recovery doesn't reassign lease
 when triggered by append()
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    [ https://issues.apache.org/jira/browse/HDFS-1142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12868541#action_12868541 ] 

Todd Lipcon commented on HDFS-1142:
-----------------------------------

bq. The test assumes that hflush() should not succeed after the recovery started, but this assumption is incorrect.

HBase is using contracts like this to do IO fencing during regionserver recovery operations (eg see discussion on HBASE-2231 and HBASE-2238). The ability to use lease recovery to lock out a writer whose soft lease has expired provides lock-like functionality tied to the storage. Without HDFS itself providing a file locking primitive, it becomes essentially impossible to do correct recovery in systems like HBase where an old writer needs to be forcibly disallowed from continued progress. Using an external system like ZK since it is asynchronous in nature.

Let me think if we have an alternate route to the same kind of behavior using the semantics you're describing.

> Lease recovery doesn't reassign lease when triggered by append()
> ----------------------------------------------------------------
>
>                 Key: HDFS-1142
>                 URL: https://issues.apache.org/jira/browse/HDFS-1142
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.21.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Blocker
>         Attachments: hdfs-1142.txt, hdfs-1142.txt
>
>
> If a soft lease has expired and another writer calls append(), it triggers lease recovery but doesn't reassign the lease to a new owner. Therefore, the old writer can continue to allocate new blocks, try to steal back the lease, etc. This is for the testRecoveryOnBlockBoundary case of HDFS-1139

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