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https://issues.apache.org/jira/browse/HBASE-1918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12767459#action_12767459
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Jonathan Gray commented on HBASE-1918:
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Patch looks good, JD. +1 for commit to branch and trunk
> Don't do DNS resolving in .META. scanner for each row
> -----------------------------------------------------
>
> Key: HBASE-1918
> URL: https://issues.apache.org/jira/browse/HBASE-1918
> Project: Hadoop HBase
> Issue Type: Improvement
> Affects Versions: 0.19.3, 0.20.1
> Reporter: Jean-Daniel Cryans
> Assignee: Jean-Daniel Cryans
> Fix For: 0.20.2, 0.21.0
>
> Attachments: HBASE-1918.patch
>
>
> While debugging a slow HBase on my new Mac, I found that my issue was that
> DNS resolving was taking 10 seconds. Since Java 1.5, many people complained
> about that and there's even a very commented issue
> (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5092063) that's closed
> but still "active". In fact the real issue here is that when you a bad DNS
> resolving (my router was acting on me, it's dead now) it waits for 10 seconds
> or something like that (see previous link). So I was running PE and my meta
> scanner was being slower and slower. In fact, everything was slow, even
> starting the shell. So using jps I found that we are resolving DNS for each
> scanned row in META in checkAssigned here:
> {code}
> if (sa != null && sa.length() > 0) {
> serverName = HServerInfo.getServerName(sa, sc);
> }
> HServerInfo storedInfo = null;
> {code}
> HSI.getServerName here creates a new HServerAddress which resolves DNS in its
> depths and it's not even necessary, we use it just to split the server IP and
> port.
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