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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-7457) DatanodeID generates excessive garbage
Date Mon, 01 Dec 2014 18:50:12 GMT

     [ https://issues.apache.org/jira/browse/HDFS-7457?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Daryn Sharp updated HDFS-7457:
    Attachment: HDFS-7457.patch

Code was split from HDFS-7433.  Changed hash regeneration to be a bit more thread-safe - compute
in a temp & assign so racing threads generate an idempotent hash.  It's a bit of a folly
though since the class is already not thread safe at all...

> DatanodeID generates excessive garbage
> --------------------------------------
>                 Key: HDFS-7457
>                 URL: https://issues.apache.org/jira/browse/HDFS-7457
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>         Attachments: HDFS-7457.patch
> {{DatanodeID#getXferAddr}} is a dynamically generated string.  This string is repeatedly
generated for the hash code, equality, comparisons, and stringification.  Every DN->NN
RPC method calls {{DatanodeManager#getDatanode}} to validate if the node is registered, which
involves a call to {{getXferAddr}}.
> The dynamic computation generates unnecessary trash that puts unnecessary pressure on
the GC.

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