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https://issues.apache.org/jira/browse/HADOOP-4472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12643406#action_12643406
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Amareshwari Sriramadasu commented on HADOOP-4472:
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bq. I don't think that is right. I think we should have a SetupTask and a
CleanupTask that are both id = 0. The isMap boolean needs to be replaced with
an enumeration. {SETUP, MAP, REDUCE, CLEANUP}. There should be tips associated
with both setup and cleanup.
This is proposed in HADOOP-4421.
bq. I don't see why the JT should ever poll the state. It knows the state
changed via the heartbeat.
Now there is no state change for setup. Both initTasks and setup happen in PREP
state.
bq. Furthermore, it should be notified again when the setup task is finished
and the rest of the job is runnable.
I think it makes sense to have RUNNABLE state, when the setup completes.
bq. I propose that we don't fix this issue at all for now. Instead we should
look at HADOOP-4421.
+1. We can add RUNNABLE state also through HADOOP-4421.
> Should we move out the creation of setup/cleanup tasks from
> JobInProgress.initTasks()?
> ---------------------------------------------------------------------------------------
>
> Key: HADOOP-4472
> URL: https://issues.apache.org/jira/browse/HADOOP-4472
> Project: Hadoop Core
> Issue Type: Improvement
> Components: mapred
> Reporter: Vivek Ratan
> Assignee: Amareshwari Sriramadasu
>
> JobInProgress.initTasks() creates TIPs for map and reduce tasks, and also the
> newly-introduced setup and cleanup tasks. initTasks() is called by the
> schedulers, as for reasons of memory optimizations, schedulers may choose to
> initialize M/R tasks at various moments (the Capacity Scheduler, for example,
> calls initTasks() just when it considers a job for running). One can say that
> Schedulers 'own' the initialization of M/R tasks in a job. Furthermore the JT
> 'owns' the setup and cleanup tasks (it schedules them, and Schedulers are
> unaware of these tasks). This causes a problematic dependency between the JT
> and a Scheduler. For example, the Capacity Scheduler calls initTasks() and
> immediately calls JobInProgress.obtainNewMapTask for a map task. This is a
> problem today, because we cannot run any map or reduce tasks before the setup
> task is run, which the Capacity Scheduler is not aware of.
> Either all Schedulers are explicitly aware of setup/cleanup tasks and their
> dependencies with M/R tasks (in which case, Schedulers 'own' the creation and
> scheduling of all these tasks correctly), or the JT 'owns' the setup/cleanup
> tasks and Schedulers are completely unaware of them (in which case, the
> creation of setup/cleanup tasks must be moved out of initTasks into a
> separate method which is called by the JT).
> I think the latter is the right way to go (unless we implement HADOOP-4421,
> in which case the former option may be viable as well).
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