On Wed, Aug 19, 2009 at 7:10 PM, Owen O'Malley <omal...@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
