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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2413) TaskTracker should handle disk failures at both startup and runtime
Date Mon, 04 Apr 2011 23:01:06 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13015675#comment-13015675
] 

Owen O'Malley commented on MAPREDUCE-2413:
------------------------------------------

The comments in configuration.c aren't correct.

The result of get_value should be released via free.
The result of extract_values and get_values should be release via free_values.

initialize_job goes past 80 chars.

We like to have braces around even single line branches in if statements. Your changes in
TaskTracker don't do that.

Why do you call localStorage.isDiskFailed and then ignore the results?

Rather than setting the "conf" attribute for the http server, you should set an attribute
with the localStorage object. All uses of MAPRED_LOCALDIR_PROPERTY should be removed, other
than the original creation of the localStorage. Furthermore, the property should never be
set.





> TaskTracker should handle disk failures at both startup and runtime
> -------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2413
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2413
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: task-controller, tasktracker
>    Affects Versions: 0.20.204.0
>            Reporter: Bharath Mundlapudi
>            Assignee: Ravi Gummadi
>             Fix For: 0.20.204.0
>
>         Attachments: MR-2413.v0.patch
>
>
> At present, TaskTracker doesn't handle disk failures properly both at startup and runtime.
> (1) Currently TaskTracker doesn't come up if any of the mapred-local-dirs is on a bad
disk. TaskTracker should ignore that particular mapred-local-dir and start up and use only
the remaining good mapred-local-dirs.
> (2) If a disk goes bad while TaskTracker is running, currently TaskTracker doesn't do
anything special. This results in either
>    (a) TaskTracker continues to "try to use that bad disk" and this results in lots of
task failures and possibly job failures(because of multiple TTs having bad disks) and eventually
these TTs getting graylisted for all jobs. And this needs manual restart of TT with modified
configuration of mapred-local-dirs avoiding the bad disk. OR
>    (b) Health check script identifying the disk as bad and the TT gets blacklisted. And
this also needs manual restart of TT with modified configuration of mapred-local-dirs avoiding
the bad disk.
> This JIRA is to make TaskTracker more fault-tolerant to disk failures solving (1) and
(2). i.e. TT should start even if at least one of the mapred-local-dirs is on a good disk
and TT should adjust its in-memory list of mapred-local-dirs and avoid using bad mapred-local-dirs.

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