Hadoop: Checkpoint Node

Checkpointing is a process of saving a snapshot of the application's/system’s state. Namenode persist its namespace in two files fsimage, edits-log.

Fsimage: It is the latest checkpoint of the namespace

edits-log: It is the log of changes to the namespace since the checkpoint.

What happens when a name node starts?

When a NameNode starts up, it merges the fsimage and edits log to provide an up-to-date view of the file system metadata.  After creating new fsimage, NameNode overwrites fsimage with the new fsmage and begins a new edits journal.

What is checkpoint node?

Checkpoint node downloads fsimage and edits from the active NameNode, merges them locally, and uploads the new image back to the active NameNode. In real time, checkpoint node runs on separate machine.

How frequently checkpoint happens?

Be default checkpoint happens for every one hour (or) when edits-log reach to 1 million records.

Previous                                                 Next                                                 Home