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From Steve Loughran <ste...@hortonworks.com>
Subject Re: Question about dead datanode
Date Mon, 24 Feb 2014 14:23:39 GMT
that's a very old version of cloudera's branch you are working with there;
patching that is not a good way to go, as you are on the slippery slope of
having your own private branch and all the costs of it.

It looks like dead node logic has -> DFSInputStream, where it is still
instance-specific:

  /* XXX Use of CocurrentHashMap is temp fix. Need to fix
   * parallel accesses to DFSInputStream (through ptreads) properly */
  private final ConcurrentHashMap<DatanodeInfo, DatanodeInfo> deadNodes =
             new ConcurrentHashMap<DatanodeInfo, DatanodeInfo>();

This implies the problem still exists -and the opportunity to fix it -but
you will need to modify your patch to apply to hadoop trunk, ideally think
of a test, then submit a patch to the HDFS project on JIRA.


On 19 February 2014 04:48, Stack <stack@duboce.net> wrote:

> On Sat, Feb 15, 2014 at 8:01 PM, Jack Levin <magnito@gmail.com> wrote:
>
> > Looks like I patched it in DFSClient.java, here is the patch:
> > https://gist.github.com/anonymous/9028934
> >
> > ....
>
>
> > I moved 'deadNodes' list outside as global field that is accessible by
> > all running threads, so at any point datanode does go down, each
> > thread is basically informed that the datanode _is_ down.
> >
>
> We need to add something like this to current versions of DFSClient, a
> global status, so each stream does not have to discover bad DNs for itself.
> St.Ack
>

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