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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3988) The elephant should remember names, not numbers.
Date Thu, 21 Aug 2008 16:18:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624412#action_12624412

Steve Loughran commented on HADOOP-3988:

Did I say you could set this on the command line? I was wrong:

you edit a properties file in the JVM lib/security directory, or call

java.security.Security.setProperty("networkaddress.cache.ttl" , "0"); 

It would be possible for server-side nodes to set this property when they start up, but the
operation should be wrapped with a catch for any security exception, so running hadoop under
a security manager isn't fatal.

-this is separate to where the hostnames should be resolved, which needs to be moved into
every services offerService loop.

Alan - I believe the Sun JVM DNS cache still ignores the TTL that comes down from above. It's
to stop applets and other sandboxed things breaking out of the sandbox and talking to hosts
behind the firewall, but interferes with long-lived server-side code.

> The elephant should remember names, not numbers.
> ------------------------------------------------
>                 Key: HADOOP-3988
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3988
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.17.2
>            Reporter: Allen Wittenauer
> The name node and the data node should not cache the resolution of host names, as doing
so prevents the use of DNS CNAMEs for any sort of fail over capability.

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