Several Hadoop daemon and Hadoop daemon

Several Hadoop daemon and Hadoop daemon

After Hadoop is installed, several processes will appear when jps is used.

Master has:

Namenode

SecondaryNameNode

JobTracker

Slaves has

Tasktracker

Datanode

1.NameNode

It is the master server in Hadoop, managing the file system namespace and accessing the files stored in the cluster.

2.SecondaryNameNode

It is not a redundant daemon of namenode, but provides periodic checkpoints and cleanup tasks.

For the sake of scalability and fault toleranceSecondaryNameNodeRun on a non-NameNode.

3.DataNode

It is responsible for managing the storage of connections to nodes (a cluster can have multiple nodes ). Each node that stores data runs a datanode daemon.

4 and 5.JobTrackerAndTaskTracker

JobTrackerSchedulingDataNode. EachDataNodeThere isTaskTracker.

JobTrackerAndTaskTrackerIn master-slave mode,JobTrackerCrossDataNodeDistribution work, whileTaskTrackerRun the task.

JobTrackerAlso checks the request work, ifDataNodeFailed for some reason,JobTrackerThe previous task is rescheduled.