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From "Harsh J (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-8134) DNS claims to return a hostname but returns a PTR record in some cases
Date Fri, 02 Mar 2012 21:33:57 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-8134?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Harsh J updated HADOOP-8134:
----------------------------

          Component/s: util
          Description: 
Per Shrijeet on HBASE-4109:

{quote}
If you are using an interface anything other than 'default' (literally that keyword) DNS.java's
getDefaultHost will return a string which will have a trailing period at the end. It seems
javadoc of reverseDns in DNS.java (see below) is conflicting with what that function is actually
doing. 

It is returning a PTR record while claims it returns a hostname. The PTR record always has
period at the end , RFC: http://irbs.net/bog-4.9.5/bog47.html

We make call to DNS.getDefaultHost at more than one places and treat that as actual hostname.

Quoting HRegionServer for example

String machineName = DNS.getDefaultHost(conf.get(
        "hbase.regionserver.dns.interface", "default"), conf.get(
        "hbase.regionserver.dns.nameserver", "default"));

We may want to sanitize the string returned from DNS class. Or better we can take a path of
overhauling the way we do DNS name matching all over.
{quote}

While HBase has worked around the issue, we should fix the methods that aren't doing what
they've intended.

1. We fix the method. This may be an 'incompatible change'. But I do not know who outside
of us uses DNS classes.
2. We fix HDFS's DN at the calling end, cause that is affected by the trailing period in its
reporting back to the NN as well (Just affects NN->DN weblinks, non critical).

For 2, we can close this and open a HDFS JIRA.

Thoughts?
             Priority: Minor  (was: Major)
     Target Version/s: 0.24.0, 0.23.3
    Affects Version/s: 0.23.0
             Assignee: Harsh J
    
> DNS claims to return a hostname but returns a PTR record in some cases
> ----------------------------------------------------------------------
>
>                 Key: HADOOP-8134
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8134
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 0.23.0
>            Reporter: Harsh J
>            Assignee: Harsh J
>            Priority: Minor
>
> Per Shrijeet on HBASE-4109:
> {quote}
> If you are using an interface anything other than 'default' (literally that keyword)
DNS.java's getDefaultHost will return a string which will have a trailing period at the end.
It seems javadoc of reverseDns in DNS.java (see below) is conflicting with what that function
is actually doing. 
> It is returning a PTR record while claims it returns a hostname. The PTR record always
has period at the end , RFC: http://irbs.net/bog-4.9.5/bog47.html
> We make call to DNS.getDefaultHost at more than one places and treat that as actual hostname.
> Quoting HRegionServer for example
> String machineName = DNS.getDefaultHost(conf.get(
>         "hbase.regionserver.dns.interface", "default"), conf.get(
>         "hbase.regionserver.dns.nameserver", "default"));
> We may want to sanitize the string returned from DNS class. Or better we can take a path
of overhauling the way we do DNS name matching all over.
> {quote}
> While HBase has worked around the issue, we should fix the methods that aren't doing
what they've intended.
> 1. We fix the method. This may be an 'incompatible change'. But I do not know who outside
of us uses DNS classes.
> 2. We fix HDFS's DN at the calling end, cause that is affected by the trailing period
in its reporting back to the NN as well (Just affects NN->DN weblinks, non critical).
> For 2, we can close this and open a HDFS JIRA.
> Thoughts?

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