[jira] [Created] (HDFS-4870) periodically re-resolve hostnames in included and excluded datanodes list

["Colin Patrick McCabe (JIRA)" <ji...@apache.org>]

Colin Patrick McCabe created HDFS-4870:
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             Summary: periodically re-resolve hostnames in included and excluded datanodes list
                 Key: HDFS-4870
                 URL: https://issues.apache.org/jira/browse/HDFS-4870
             Project: Hadoop HDFS
          Issue Type: Improvement
            Reporter: Colin Patrick McCabe
            Priority: Minor


We currently only resolve the hostnames in the included and excluded datanodes list once-- when the list is read.  The rationale for this is that in big clusters, DNS resolution for thousands of nodes can take a long time (when generating a datanode list in getDatanodeListForReport, for example).  However, if the DNS information changes for one of these hosts, we should reflect that.  A background thread could do these DNS resolutions every few minutes without blocking any foreground operations.

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