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Posted to common-issues@hadoop.apache.org by "Andrew Otto (JIRA)" <ji...@apache.org> on 2013/12/24 19:44:50 UTC

[jira] [Created] (HADOOP-10181) GangliaContext does not work with multicast ganglia setup

Andrew Otto created HADOOP-10181:
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             Summary: GangliaContext does not work with multicast ganglia setup
                 Key: HADOOP-10181
                 URL: https://issues.apache.org/jira/browse/HADOOP-10181
             Project: Hadoop Common
          Issue Type: Bug
            Reporter: Andrew Otto
            Priority: Minor


The GangliaContext class which is used to send Hadoop metrics to Ganglia uses a DatagramSocket to send these metrics.  This works fine for Ganglia multicast setups that are all on the same VLAN.  However, when working with multiple VLANs, a packet sent via DatagramSocket to a multicast address will end up with a TTL of 1.  Multicast TTL indicates the number of network hops for which a particular multicast packet is valid.  The packets sent by GangliaContext do not make it to ganglia aggregrators on the same multicast group, but in different VLANs.

To fix, we'd need a configuration property that specifies that multicast is to be used, and another that allows setting of the multicast packet TTL.  With these set, we could then use MulticastSocket setTimeToLive() instead of just plain ol' DatagramSocket.




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