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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-5399) Revisit SafeModeException and corresponding retry policies
Date Wed, 05 Feb 2014 00:56:09 GMT

     [ https://issues.apache.org/jira/browse/HDFS-5399?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HDFS-5399:
------------------------------

    Attachment: hdfs-5399.002.patch

The issue was that the convenience constructors for FailoverOnNetworkExceptionRetry didn't
maintain the old behavior of retrying multiple times, since they set numRetries to 0. This
new patch sets numRetries to Integer.MAX_VALUE for those constructors, and fixes the test.

> Revisit SafeModeException and corresponding retry policies
> ----------------------------------------------------------
>
>                 Key: HDFS-5399
>                 URL: https://issues.apache.org/jira/browse/HDFS-5399
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.3.0
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-5399.000.patch, HDFS-5399.001.patch, hdfs-5399.002.patch
>
>
> Currently for NN SafeMode, we have the following corresponding retry policies:
> # In non-HA setup, for certain API call ("create"), the client will retry if the NN is
in SafeMode. Specifically, the client side's RPC adopts MultipleLinearRandomRetry policy for
a wrapped SafeModeException when retry is enabled.
> # In HA setup, the client will retry if the NN is Active and in SafeMode. Specifically,
the SafeModeException is wrapped as a RetriableException in the server side. Client side's
RPC uses FailoverOnNetworkExceptionRetry policy which recognizes RetriableException (see HDFS-5291).
> There are several possible issues in the current implementation:
> # The NN SafeMode can be a "Manual" SafeMode (i.e., started by administrator through
CLI), and the clients may not want to retry on this type of SafeMode.
> # Client may want to retry on other API calls in non-HA setup.
> # We should have a single generic strategy to address the mapping between SafeMode and
retry policy for both HA and non-HA setup. A possible straightforward solution is to always
wrap the SafeModeException in the RetriableException to indicate that the clients should retry.



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