Hadoop: How do datanodes register with the namenode? -


do hadoop datanodes register namenode calling namenode, or namenode have list of datanodes , reaches out them.

i want understand better troubleshoot problem new namenode brought (after namenode failure) doesn't see of datanodes (but has fsimage correct).

data nodes heartbeat in name node. name node not reach out data nodes.

even when retrieving data, name node not reach out data nodes. name node inform client data , client retrieve data nodes. (to clarify, during mr workflow job tracker finds name node data , assigns task trackers appropriately.)


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