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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (HADOOP-3620) Namenode should synchronously resolve a datanode's network location when the datanode registers
Date Fri, 18 Jul 2008 01:17:31 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614598#action_12614598
] 

rangadi edited comment on HADOOP-3620 at 7/17/08 6:16 PM:
---------------------------------------------------------------

One way to move the resolution out of global lock :

resolveNetworkLocation does not strictly need DatanodeDescriptor.
So regeisterDatanode() could look something like :
{code}
 public void public synchronized void registerDatanode(DatanodeRegistration nodeReg) 
                                                    throws IOException {
     String networkLocation = resolveNeworklocation(nodeReg.getHost());
     internalRegisterDatanode(nodeReg, networkLocation); //holds global lock.
}
{code}
Does the above work?

Note that pre-resolving hosts in include file might not help start up since
 * resolving serially at the beginning still increases the start up time.
 * "normalizing host names" does multiple DNS resolves.


      was (Author: rangadi):
    One way to move the resolution out of global lock :

resolveNetworkLocation does not strictly need DatanodeDescriptor.
So regeisterDatanode() could look something like :
{code}
 public void public synchronized void registerDatanode(DatanodeRegistration nodeReg) 
                                                                                         
         throws IOException {
     String networkLocation = resolveNeworklocation(nodeReg.getHost());
     internalRegisterDatanode(nodeReg, networkLocation); //holds global lock.
}
{code}
Does the above work?

Note that pre-resolving hosts in include file might not help start up since
 * resolving serially at the beginning still increases the start up time.
 * "normalizing host names" does multiple DNS resolves.

  
> Namenode should synchronously resolve a datanode's network location when the datanode
registers
> -----------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-3620
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3620
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.18.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.19.0
>
>         Attachments: netResolution.patch, netResolution1.patch, netResolution2.patch,
netResolution3.patch, netResolution4.patch
>
>
> Release 0.18.0 removes the rpc timeout. So the namenode is ok to resolve a datanode's
network location when the datanode registers. This could remove quite a lot of unnecessary
code in both datanode and namenode to handle asynchronous network location resolution and
avoid many potential bugs.

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