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https://issues.apache.org/jira/browse/HADOOP-3987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12624365#action_12624365
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Steve Loughran commented on HADOOP-3987:
----------------------------------------
Here is the specific problems that appear to exist, though I could of course be
mistaken.
1. All RemoteExceptions that are not an instance of
DisallowedTaskTrackerException are ignored, nothing is even printed
return State.STALE;
} catch (RemoteException re) {
String reClass = re.getClassName();
if (DisallowedTaskTrackerException.class.getName().equals(reClass)) {
LOG.info("Tasktracker disallowed by JobTracker.");
return State.DENIED;
}
2. All IOExceptions are logged, but not reported up; the service remains in the
inner (sleepless) while loop.
} catch (IOException except) {
String msg = "Caught exception: " + except.getMessage();
LOG.error(msg, except);
}
}
This may not be the best way to handle network and IO problems.
3. the code that checks for the system directory off the job service will throw
an IOException if none is provided, and exception that will be caught and
logged in the code in (2). If a JobTracker is returning null to
getSystemDir(), then every TaskTracker that is bonded to it is going to spin,
calling getSystemDir() on the server, logging the error and repeating, without
any delay at all.
I'm not sure what the ideal exception handling policy here should be, but what
is there today has weaknesses. If the network is playing up, logging
RemoteExceptions and maybe inserting delays would be good; if
JobTracker.getSystemDir() is null then the clients should sleep longer in the
hope that someone will fix the job tracker, rather than spinning.
> TaskTracker.offerService could handle IO and Remote Exceptions better
> ---------------------------------------------------------------------
>
> Key: HADOOP-3987
> URL: https://issues.apache.org/jira/browse/HADOOP-3987
> Project: Hadoop Core
> Issue Type: Bug
> Affects Versions: 0.19.0
> Reporter: Steve Loughran
>
> The core offerService() loop has a try/catch wrapper that catches and
> processes exceptions. Most cause offerService() to return, which then
> triggers a sleep and restart in the main loop. But some exceptions are just
> logged and ignored, which may be inappropriate
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