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From "B. X." <bxi...@gmail.com>
Subject Re: different modes of inter process communication
Date Wed, 16 Sep 2009 18:49:15 GMT
On Wed, Aug 19, 2009 at 7:10 PM, Owen O'Malley <omalley@apache.org> wrote:

Thank you both for clearing it up.

I have another related question:  my understanding is that basic
heartbeat mechanism are used to keep different roles (namenode,
datanode, tasktracker etc) aware of each other, but I am not able to
observe this in the log.   For example, if I use the sigstop/sigcont
mechanism to stop the namenode jvm process for 30 seconds and then
continue, I don't observe any extra communications due to supposedly
missed heartbeat.  (I checked the dfs.heartbeat.interval is set to 3
seconds).  Rather, what I saw is all roles seem to stop in unison for
30 seconds (by the fact that no log events in the same time window).

I would appreciate some pointers on how heartbeats are used and configured.

-Bin

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