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From "Mukul Kumar Singh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12813) RequestHedgingProxyProvider can hide Exception thrown from the Namenode for proxy size of 1
Date Sat, 18 Nov 2017 05:05:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16257924#comment-16257924

Mukul Kumar Singh commented on HDFS-12813:

    Let's have two unwrap methods to handle two different cases
bq. Done

    Also, the parameter of these two methods should be ExecutionException or InvocationTargetException
instead of Exception.
bq. Done

    Pass the unwrapped exception to logProxyException. Then, isStandbyException does not need
to unwrap it again.
bq. Done

    Question: It seems to me that the code expects either ExecutionException or InvocationTargetException,
could we catch either ExecutionException or InvocationTargetException instead of Exception?
bq. Done

    Question: the patch changes successfulProxy to lastUsedProxy. Then, getProxy() may return
"last unsuccessful proxy". Is it okay?
bq. I looked into the code and figured that a proxy will be used for {{expectedFailoverCount}}
in RetryInvocationHandler#failover before the currently used proxy is being rejected. So I
feel it is fine that {{currentUsedProxy}} will be reused.

> RequestHedgingProxyProvider can hide Exception thrown from the Namenode for proxy size
of 1
> -------------------------------------------------------------------------------------------
>                 Key: HDFS-12813
>                 URL: https://issues.apache.org/jira/browse/HDFS-12813
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha
>            Reporter: Mukul Kumar Singh
>            Assignee: Mukul Kumar Singh
>         Attachments: HDFS-12813.001.patch, HDFS-12813.002.patch, HDFS-12813.003.patch
> HDFS-11395 fixed the problem where the MultiException thrown by RequestHedgingProxyProvider
was hidden. However when the target proxy size is 1, then unwrapping is not done for the InvocationTargetException.
for target proxy size of 1, the unwrapping should be done till first level where as for multiple
proxy size, it should be done at 2 levels.

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