The secondary namenode is a checkpoint service for the namenode daemon that performs periodic merging of the edits log and the fsimage file. The secondary namenode UI can be accessed using the following URL:
http://<secondary-namenode-server>:50090/
The following screenshot shows the secondary namenode UI:
Just like the namenode UI, the secondary namenode UI also displays the Hadoop version. All checkpoint related information is available in this UI, which are given as follows:
- Name Node Address: This is the RPC address of the primary namenode daemon. Secondary namenode uses this address to connect to primary namenode.
- Start Time: This is the start timestamp of the secondary namenode service.
- Last Checkpoint Time: This the timestamp of the last checkpoint action performed by the secondary namenode daemon.
- Checkpoint Period: This property defines the schedule to perform the checkpoint. In the preceding screenshot, the value is 3,600 seconds. This means that every 3,600 seconds (1 hour), the secondary namenode daemon will perform the checkpoint operation.
- Checkpoint Size: If the
editslogfile reaches this checkpoint size, the secondary namenode daemon will perform the checkpoint even if the check point period has not elapsed. - Checkpoint Dirs: This is the location of the
fsimagefile stored by the secondary namenode daemon. - Checkpoint Edit Dirs: This is the location of the
editslogfiles stored by the secondary namenode daemon.
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