Nicolas Liochon created HDFS-4754:
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Summary: Add an API in the namenode to mark a datanode as stale
Key: HDFS-4754
URL: https://issues.apache.org/jira/browse/HDFS-4754
Project: Hadoop HDFS
Issue Type: Improvement
Components: hdfs-client, namenode
Reporter: Nicolas Liochon
Priority: Critical
There is a detection of the stale datanodes in HDFS since HDFS-3703, with a
timeout, defaulted to 30s.
There are two reasons to add an API to mark a node as stale even if the timeout
is not yet reached:
1) ZooKeeper can detect that a client is dead at any moment. So, for HBase, we
sometimes start the recovery before a node is marked staled. (even with
reasonable settings as: stale: 20s; HBase ZK timeout: 30s
2) Some third parties could detect that a node is dead before the timeout,
hence saving us the cost of retrying. An example or such hw is Arista,
presented here by [~tsuna]
http://tsunanet.net/~tsuna/fsf-hbase-meetup-april13.pdf, and confirmed in
HBASE-6290.
As usual, even if the node is dead it can comeback before the 10 minutes limit.
So I would propose to set a timebound. The API would be
namenode.markStale(String ipAddress, int port, long durationInMs);
After durationInMs, the namenode would again rely only on its heartbeat to
decide.
Thoughts?
If there is no objections, and if nobody in the hdfs dev team has the time to
spend some time on it, I will give it a try for branch 2 & 3.
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