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https://issues.apache.org/jira/browse/HDFS-14116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16710791#comment-16710791
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Chen Liang commented on HDFS-14116:
-----------------------------------
Thanks for the finding [~shv], seems this error is different though. Because
this is triggering a different code path, causing a different class casting.
For fsck to work, as a current workaround, we can override configs to use
configured proxy provider in the fsck command. For example if we have
fs.defaultFS=ns1, we can call fsck as
{code}
hdfs fsck -Ddfs.client.failover.proxy.provider.ns1= \
org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider
hdfs://ns1/<path>
{code}
Still need to fix this though.
> Fix a potential class cast error in ObserverReadProxyProvider
> -------------------------------------------------------------
>
> Key: HDFS-14116
> URL: https://issues.apache.org/jira/browse/HDFS-14116
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Reporter: Chen Liang
> Assignee: Chao Sun
> Priority: Major
>
> Currently in {{ObserverReadProxyProvider}} constructor there is this line
> {code}
> ((ClientHAProxyFactory<T>) factory).setAlignmentContext(alignmentContext);
> {code}
> This could potentially cause failure, because it is possible that factory can
> not be casted here. Specifically,
> {{NameNodeProxiesClient.createFailoverProxyProvider}} is where the
> constructor will be called, and there are two paths that could call into this:
> (1).{{NameNodeProxies.createProxy}}
> (2).{{NameNodeProxiesClient.createFailoverProxyProvider}}
> (2) works fine because it always uses {{ClientHAProxyFactory}} but (1) uses
> {{NameNodeHAProxyFactory}} which can not be casted to
> {{ClientHAProxyFactory}}, this happens when, for example, running
> NNThroughputBenmarck. To fix this we can at least:
> 1. introduce setAlignmentContext to HAProxyFactory which is the parent of
> both ClientHAProxyFactory and NameNodeHAProxyFactory OR
> 2. only setAlignmentContext when it is ClientHAProxyFactory by, say, having a
> if check with reflection.
> Depending on whether it make sense to have alignment context for the case (1)
> calling code paths.
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