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From "Chengbing Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7798) Checkpointing failure caused by shared KerberosAuthenticator
Date Sun, 15 Feb 2015 03:16:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7798?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14321793#comment-14321793

Chengbing Liu commented on HDFS-7798:

The checkpointing failure happens when image uploading and edit log fetching comes at the
same time.

> Checkpointing failure caused by shared KerberosAuthenticator
> ------------------------------------------------------------
>                 Key: HDFS-7798
>                 URL: https://issues.apache.org/jira/browse/HDFS-7798
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: security
>            Reporter: Chengbing Liu
>            Assignee: Chengbing Liu
>            Priority: Critical
>         Attachments: HDFS-7798.01.patch
> We have observed in our real cluster occasional checkpointing failure. The standby NameNode
was not able to upload image to the active NameNode.
> After some digging, the root cause appears to be a shared {{KerberosAuthenticator}} in
{{URLConnectionFactory}}. The authenticator is designed as a use-once instance, and is not
stateless. It has attributes such as {{HttpURLConnection}} and {{URL}}. When multiple threads
are calling {{URLConnectionFactory#openConnection(...)}}, the shared authenticator is going
to have race condition, resulting in a failed image uploading.
> Therefore for the first step, without breaking the current API, I propose we create a
new {{KerberosAuthenticator}} instance for each connection, to make checkpointing work. We
may consider making {{Authenticator}} design and implementation stateless afterwards, as {{ConnectionConfigurator}}

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