Cluster-Wide Blacklisting
A TaskTracker can be blacklisted cluster-wide for any of the following reasons:
- The number of blacklists from successful jobs (the fault count) exceeds
mapred.max.tracker.blacklists
.NOTE:The parameter
mapred.job.impact.blacklisting
in themapred-site.xml
file lets you specify whether job failures should count toward the threshold set withmapred.max.tracker.blacklists
. This parameter can be helpful when you are testing and know that jobs are likely to fail. - The TaskTracker has been manually blacklisted using
hadoop job -blacklist-tracker <host>
- The status of the TaskTracker (as reported by a user-provided health-check script) is not healthy
If a TaskTracker is blacklisted, any currently running tasks are allowed to finish, but no
further tasks are scheduled. If a TaskTracker has been blacklisted due to
mapred.max.tracker.blacklists
or using the hadoop job
-blacklist-tracker <host>
command, un-blacklisting requires a TaskTracker
restart.
Only 50% of the TaskTrackers in a cluster can be blacklisted at any one time.
After 24 hours, the TaskTracker is automatically removed from the blacklist and can accept jobs again.