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https://issues.apache.org/jira/browse/MAPREDUCE-2413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13021854#comment-13021854
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Owen O'Malley commented on MAPREDUCE-2413:
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The comment on get_value should be:
{code}
/*
* function used to get a configuration value.
* The function for the first time populates the configuration details into
* array, next time onwards uses the populated array.
*
* Memory returned here should be freed using free.
*/
{code}
free_values should be commented as:
{code}
// free an entry set of values
void free_values(char** values) {
if (*values != NULL) {
// the values were tokenized from the same malloc, so freeing the first
// frees the entire block.
free(*values);
}
if (values != NULL) {
free(values);
}
}
{code}
> 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.v0.1.patch, 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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