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From "Gary Helmling (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15856) Cached Connection instances can wind up with addresses never resolved
Date Sat, 21 May 2016 00:07:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15294566#comment-15294566

Gary Helmling commented on HBASE-15856:

Looks like this may have broken TestMasterFailover in branch-1 and older.  I'm taking a look
at it. If I can't come up with a solution tonight, I'll revert from those branches.

> Cached Connection instances can wind up with addresses never resolved
> ---------------------------------------------------------------------
>                 Key: HBASE-15856
>                 URL: https://issues.apache.org/jira/browse/HBASE-15856
>             Project: HBase
>          Issue Type: Bug
>          Components: Client
>            Reporter: Gary Helmling
>            Assignee: Gary Helmling
>            Priority: Critical
>             Fix For: 2.0.0, 1.3.0, 1.2.2, 0.98.20, 1.1.6
>         Attachments: HBASE-15856.001.patch, HBASE-15856.002.patch, HBASE-15856.003.patch
> During periods where DNS is not working properly, we can wind up caching connections
to master or regionservers where the initial hostname resolution and the resolution is never
re-attempted.  This means that clients will forever get UnknownHostException for any calls.
> When constructing a BlockingRpcChannelImplementation, we instantiate the InetSocketAddress
to use for the connection.  This instance is then used in the rpc client connection, where
we check isUnresolved() and throw an UnknownHostException if that returns true.  However,
at this point the rpc channel is already cached in the HConnectionImplementation map of stubs.
 So at this point it will never be resolved.
> Setting the config for hbase.resolve.hostnames.on.failure masks this issue, since the
stub key used is modified to contain the address.  However, even in that case, if DNS fails,
an rpc channel instance with unresolved ISA will still be cached in the stubs under the hostname
only key.

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