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Jan 11 in Big Data | Hadoop

Q: What are the two messages that NameNode receives from DataNode in Hadoop?

1 Answer

Jan 11

NameNode receives following two messages from every DataNode:

1. Heartbeat: This message signals that DataNode is still alive. Periodic receipt of Heartbeat is vey important for NameNode to decide whether to use a DataNode

 

or not.

2. Block Report: This is a list of all the data blocks hosted on a DataNode. This report is also very useful for functioning of NameNode. With this report, NameNode gets information about what data is stored on a specific DataNode.

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