[jira] [Created] (HDFS-9945) Datanode command for evicting writers

["Kihwal Lee (JIRA)" <ji...@apache.org>]

Kihwal Lee created HDFS-9945:
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             Summary: Datanode command for evicting writers
                 Key: HDFS-9945
                 URL: https://issues.apache.org/jira/browse/HDFS-9945
             Project: Hadoop HDFS
          Issue Type: New Feature
          Components: datanode
            Reporter: Kihwal Lee


It will be useful if there is a command to evict writers from a datanode. When a set of datanodes are being decommissioned, they can get blocked by slow writers at the end.  It was rare in the old days since mapred jobs didn't last too long, but with many different types of apps running on today's YARN cluster, we are often see very long tail in datanode decommissioning.

I propose a new dfsadmin command, {{evictWriters}}, to be added. I initially thought about having namenode automatically telling datanodes on decommissioning, but realized that having a command is more flexible. E.g. users can choose not to do this at all, choose when to evict writers, or whether to try multiple times for whatever reasons.



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