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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