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Posted to issues@spark.apache.org by "Luca Canali (JIRA)" <ji...@apache.org> on 2018/09/03 19:14:02 UTC
[jira] [Closed] (SPARK-21829) Enable config to permanently
blacklist a list of nodes
[ https://issues.apache.org/jira/browse/SPARK-21829?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Luca Canali closed SPARK-21829.
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> Enable config to permanently blacklist a list of nodes
> ------------------------------------------------------
>
> Key: SPARK-21829
> URL: https://issues.apache.org/jira/browse/SPARK-21829
> Project: Spark
> Issue Type: New Feature
> Components: Scheduler, Spark Core
> Affects Versions: 2.1.1, 2.2.0
> Reporter: Luca Canali
> Priority: Minor
>
> The idea for this proposal comes from a performance incident in a local cluster where a job was found very slow because of a log tail of stragglers due to 2 nodes in the cluster being slow to access a remote filesystem.
> The issue was limited to the 2 machines and was related to external configurations: the 2 machines that performed badly when accessing the remote file system were behaving normally for other jobs in the cluster (a shared YARN cluster).
> With this new feature I propose to introduce a mechanism to allow users to specify a list of nodes in the cluster where executors/tasks should not run for a specific job.
> The proposed implementation that I tested (see PR) uses the Spark blacklist mechanism. With the parameter spark.blacklist.alwaysBlacklistedNodes, a list of user-specified nodes is added to the blacklist at the start of the Spark Context and it is never expired.
> I have tested this on a YARN cluster on a case taken from the original production problem and I confirm a performance improvement of about 5x for the specific test case I have. I imagine that there can be other cases where Spark users may want to blacklist a set of nodes. This can be used for troubleshooting, including cases where certain nodes/executors are slow for a given workload and this is caused by external agents, so the anomaly is not picked up by the cluster manager.
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