[
https://issues.apache.org/jira/browse/HADOOP-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12637007#action_12637007
]
Amar Kamat commented on HADOOP-4018:
------------------------------------
Few comments
1)
{code}
int maxTasks = conf.getInt("mapred.jobtracker.maxtasks.per.job", -1);
{code}
This will change per job as _conf_ is configured per job. Hence all the jobs
should get this value from the jobtracker. Something like
{code}
-----JobTracker-------------
int getMaxTasksPerJob() {
return conf.get("mapred.jobtracker.maxtasks.per.job", -1);
}
-----JobInProgress---------
int maxTasks = jobtracker.getMaxTasks();
{code}
2)
{code}
if (maxTasks != -1 && numMapTasks + numReduceTasks > maxTasks) {
{code}
What is I pass _-2_? So the check should be
{code}
if (maxTasks > 0 && numMapTasks + numReduceTasks > maxTasks) {
{code}
3)
{code}
if (maxTasks != -1 && numMapTasks + numReduceTasks > maxTasks) {
long now = System.currentTimeMillis();
this.finishTime = now;
status.setRunState(JobStatus.FAILED);
JobHistory.JobInfo.logFailed(profile.getJobID(), now, 0, 0);
// Special case because the Job is not queued
JobEndNotifier.registerNotification(this.getJobConf(), this.getStatus());
throw new IOException(
"The number of tasks for this job " +
(numMapTasks + numReduceTasks) +
" exceeds the configured limit " + maxTasks);
}
{code}
can be written as
{code}
if (maxTasks > 0 && numMapTasks + numReduceTasks > maxTasks) {
throw new IOException(
"The number of tasks for this job " +
(numMapTasks + numReduceTasks) +
" exceeds the configured limit " + maxTasks);
}
{code}
Note that whatever you have done should be done by the job upon failure i.e
- setting the runstate to {{FAILED}}
- setting the finish time
- logging failure to history and hence closing the file.
4) One minor nit. _mapred.jobtracker.maxtasks.per.job_ could be
_mapred.job.tasks.maximum_
The test case looks fine. Plz check with everyone if passing -1 for _UNLIMITED_
is fine. Wondering what is 0 is passed? Should be bail out immediately or
should we consider any non-positive number as _UNLIMITED_?
> limit memory usage in jobtracker
> --------------------------------
>
> Key: HADOOP-4018
> URL: https://issues.apache.org/jira/browse/HADOOP-4018
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: maxSplits.patch, maxSplits2.patch, maxSplits3.patch,
> maxSplits4.patch, maxSplits5.patch, maxSplits6.patch, maxSplits7.patch,
> maxSplits8.patch, maxSplits9.patch
>
>
> We have seen instances when a user submitted a job with many thousands of
> mappers. The JobTracker was running with 3GB heap, but it was still not
> enough to prevent memory trashing from Garbage collection; effectively the
> Job Tracker was not able to serve jobs and had to be restarted.
> One simple proposal would be to limit the maximum number of tasks per job.
> This can be a configurable parameter. Is there other things that eat huge
> globs of memory in job Tracker?
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
