[jira] Commented: (HADOOP-4421) Rework job-setup and job-cleanup tasks

["Devaraj Das (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-4421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12698358#action_12698358 ] 

Devaraj Das commented on HADOOP-4421:
-------------------------------------

I am +1 for the enum for TaskTypes.

There are two approaches to having slots for the setup/cleanup tasks -
1) Have a special slot in the TT for all the special tasks - JobSetup, JobCleanup and TaskCleanup. This special slot can run any of the special tasks. With this setup, we have three types of slots in the TT - Map, Reduce, and Setup/Cleanup slot.
2) Have the Map slots in the TT be floating between the actual maps and the special tasks. In this model, one would configure #Reduce slots in the TT, and "#other slots".

The other thing that I am thinking of removing is the reuse of taskattemptID for the cleanup tasks (as implemented in HADOOP-4759). Made the code hard to read/maintain. 

Thoughts?


> Rework job-setup and job-cleanup tasks
> --------------------------------------
>
>                 Key: HADOOP-4421
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4421
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Arun C Murthy
>             Fix For: 0.20.0
>
>
> Currently we have a notion of map-{setup|cleanup} TIP and reduce-{setup|cleanup} TIP of which only 1 setup and cleanup tasks are picked by the JobInProgress. Also a lot of state-maintenence of these TIPs are done by the JobInProgress itself, outside of the more logical place i.e. TaskInProgress.
> We really should rework this to have a single setup and cleanup task which isn't associated with a map or reduce task i.e. into separate task _types_. What we have currently is quite ungainly and hard to maintain.

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