HDFS - Heartbeat (Dead datanode)

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Each DataNode sends a Heartbeat message to the NameNode periodically.

The NameNode marks DataNodes without recent Heartbeats as dead and does not forward any new IO requests to them.


The time-out to mark DataNodes dead is conservatively long (over 10 minutes by default) in order to avoid replication storm caused by state flapping of DataNodes.


hdfs getconf -confKey dfs.heartbeat.interval

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