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Date: Tue, 14 May 2013 02:35:16 +0000 (UTC)
From: "Andrew Wang (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12647142.1368231955663.313708.1368498916163@arcas>
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Subject: [jira] [Updated] (HDFS-4816) transitionToActive blocks if the SBN
 is doing checkpoint image transfer
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     [ https://issues.apache.org/jira/browse/HDFS-4816?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Wang updated HDFS-4816:
------------------------------

    Attachment: hdfs-4816-1.patch

Here's a patch making it into a thread. I've tested this manually with a pseudo-distributed HA cluster, and am able to transition from standby to active without blocking on the transfer.

Making a unit test for this is proving difficult. Posting it up for now sans test.
                
> transitionToActive blocks if the SBN is doing checkpoint image transfer
> -----------------------------------------------------------------------
>
>                 Key: HDFS-4816
>                 URL: https://issues.apache.org/jira/browse/HDFS-4816
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 3.0.0, 2.0.4-alpha
>            Reporter: Andrew Wang
>         Attachments: hdfs-4816-1.patch
>
>
> The NN and SBN do this dance during checkpoint image transfer with nested HTTP GETs via {{HttpURLConnection}}. When an admin does a {{-transitionToActive}} during this transfer, part of that is interrupting an ongoing checkpoint so we can transition immediately.
> However, the {{thread.interrupt()}} in {{StandbyCheckpointer#stop}} gets swallowed by {{connection.getResponseCode()}} in {{TransferFsImage#doGetUrl}}. None of the methods in HttpURLConnection throw InterruptedException, so we need to do something else (perhaps HttpClient [1]):
> [1]: http://hc.apache.org/httpclient-3.x/

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