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  1. Hadoop HDFS
  2. HDFS-9945

Datanode command for evicting writers

    Details

    • Type: New Feature
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: 2.8.0, 3.0.0-alpha1
    • Component/s: datanode
    • Labels:
      None
    • Target Version/s:
    • Hadoop Flags:
      Reviewed
    • Release Note:
      Hide
      This new dfsadmin command, evictWriters, stops active block writing activities on a data node. The affected writes will continue without the node after a write pipeline recovery. This is useful when data node decommissioning is blocked by slow writers. If issued against a non-decommissioing data node, all current writers will be stopped, but new write requests will continue to be served.
      Show
      This new dfsadmin command, evictWriters, stops active block writing activities on a data node. The affected writes will continue without the node after a write pipeline recovery. This is useful when data node decommissioning is blocked by slow writers. If issued against a non-decommissioing data node, all current writers will be stopped, but new write requests will continue to be served.

      Description

      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.

        Attachments

        1. HDFS-9945.patch
          18 kB
          Kihwal Lee
        2. HDFS-9945.v2.patch
          18 kB
          Kihwal Lee

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              • Assignee:
                kihwal Kihwal Lee
                Reporter:
                kihwal Kihwal Lee
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                Dates

                • Created:
                  Updated:
                  Resolved: