DATABASE FUNDAMENTALS
BASICS OF BIG DATA
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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datapulse
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h-signal
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heartbeats
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Active-pulse
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Detailed explanation-1: -A ‘heartbeat’ is a signal sent between a DataNode and NameNode. This signal is taken as a sign of vitality. If there is no response to the signal, then it is understood that there are certain health issues/ technical problems with the DataNode or the TaskTracker. The default heartbeat interval is 3 seconds.
Detailed explanation-2: -If the DataNode in HDFS does not send heartbeat to NameNode in ten minutes, then NameNode considers the DataNode to be out of service and the Blocks replicas hosted by that DataNode to be unavailable. The NameNode then schedules the creation of new replicas of those blocks on other DataNodes.
Detailed explanation-3: -During normal operation, DataNodes send heartbeats to the NameNode to confirm that the DataNode is operating and the block replicas it hosts are available. The default heartbeat interval is three seconds.
Detailed explanation-4: -Datanodes in HDFS Datanodes are responsible for storing, retrieving, replicating, deletion, etc. of blocks when asked by the Namenode. They periodically send heartbeats to the Namenode so that it is aware of their health.