This topic contains 2 replies, has 1 voice, and was last updated by  dfbdteam3 4 months ago.

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  • #5754

    dfbdteam3
    Moderator

    How often datanode send heartbeat to namenode. How long namenode wait for heartbeat before it consider datanode as dead node ?

    #5755

    dfbdteam3
    Moderator

    In HDFS DataNodes sends the heartbeat to NameNode in every “3 sec”(Default value of heartbeat.interval is 3 seconds.)

    Heartbeat interval can be set in hdfs-site.xml as follows:

    <property>
    <name>heartbeat.recheck.interval</name>
    <value>15</value>
    <description>Determines data node heartbeat interval in seconds.</description>
    </property>

    Timeout = 2 * heartbeat.recheck.interval + 10 * heartbeat.interval.
    After which namenode will consider the datanode as a dead node and namenode stops sending I/O requests to this datanode. NameNode then schedules the creation of replicas of those Data Blocks on another datanodes.

    For more details please refer: HDFS Read-Write operations

    #5757

    dfbdteam3
    Moderator

    Datanodes sends heartbeats to Namenodes to apprise that its that it is alive and working. In this heartbeats the datanodes also send the information like the total disk space, total space in use and the data transfers in the process, It helps namenode to perform load balancing.

    By default, the heartbeat interval is 3 seconds. If the Namenode doesn’t get any heartbeat, it waits for 10 minutes and considers the Datanode as dead. When Namenode declares any datanode dead, it replicates the blocks stored on the dead datanode to other working nodes for data availability.

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