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https://issues.apache.org/jira/browse/HBASE-1918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12767679#action_12767679
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stack commented on HBASE-1918:
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So, once cached, it can never change. I suppose this is fine. Maybe one day
when we grow up and we have hbase clusters of 1k hosts and we need to support
machines changing IPs, we can use something like http://www.xbill.org/dnsjava/
to manage our dns cache. Meantime, patch looks good to me. +1.
> 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-1918-2.patch, HBASE-1918-3.patch, 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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