What happens when the NameNode is down?

When the NameNode goes down, the file system goes offline. There is an optional SecondaryNameNode that can be hosted on a separate machine. It only creates checkpoints of the namespace by merging the edits file into the fsimage file and does not provide any real redundancy.

What happens when a NameNode fails in Hadoop?

If NameNode gets fail the whole Hadoop cluster will not work. Actually, there will not any data loss only the cluster work will be shut down, because NameNode is only the point of contact to all DataNodes and if the NameNode fails all communication will stop.

What happens when a job is submitted in Hadoop?

Your answer Now, i once your job has been submitted the Resource Manager will assign a new application id to this job which will be then passed on to the client. Client will copy the jar file and other job resources to HDFS. Basically, client submits the job through Resource Manager.

Can you recover a NameNode when it is down?

When a name node fails, it is possible to recover from a previous checkpoint generated by Secondary Namenode. Secondary Namenode performs periodic checkpoint process.

What happens when a user submits a Hadoop job when the NameNode is down?

By Hadoop job, you probably mean MapReduce job. If your NN is down, and you don’t have spare one (in HA setup) your HDFS will not be working and every component dependent on this HDFS namespace will be either stuck or crashed.

What is the role of a NameNode?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. When the NameNode goes down, the file system goes offline.

How does NameNode work in Hadoop?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. The NameNode is a Single Point of Failure for the HDFS Cluster. When the NameNode goes down, the file system goes offline.

What happens when a user submits a Hadoop job when the Namenode is down?

What happens when a user submits a Hadoop job when the job tracker is down does the job get in to hold or does it fail?

When a user submits a job, the client get a new application id for this particular job. It will check for the output directory that was passed and will copy the jar and other resources to HDFS. It wont be able to connect to HDFS since the Namenode is down , the job will not be submitted and it will fail.

What is NameNode?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. It does not store the data of these files itself. When the NameNode goes down, the file system goes offline.

What is NameNode recovery process?

The lease recovery process is triggered on the NameNode to recover leases for a given client, either by the monitor thread upon hard limit expiry, or when a client tries to take over lease from another client when the soft limit expires.

When Namenode fails which node takes the responsibility of active node in Hadoop?

When active node fails, then Passive node takes the responsibility of active node. Passive node is also called standby namenode that takes the responsibility to remove the problem of single point of failure (SPOF).