Adding a RegionServer dynamically to a running HBase Cluster
Being able to add RegionServers dynamically without bringing
down the entire cluster is quite a significant requirement and at the same time
damn easy.
Step 1: Edit $HBASE_HOME/conf/regionservers on the Master node
and add the new address.
Step 2: Setup the new node with needed software, permissions.
Step 3: On that node run
$HBASE_HOME/bin/hbase-daemon.sh start regionserver
Confirm it worked by looking at the Master's web UI or in that
region server's log.
That’s it. You’re done.
Removing/Decommissioning a RegionServer dynamically from a
running HBase Cluster
Just as significant as being able to add a RegionServer to an
HBase Cluster dynamically is essential, just that important it is to be able to
remove one.
And you can be happy that it is just a matter of two steps.
Step 1: On the node to be removed run
$HBASE_HOME/bin/hbase-daemon.sh stop regionserver
Step 2: Edit $HBASE_HOME/conf/regionservers on the Master node
and remove the address of the particular node being removed.
You can check the UI to ensure the node has been removed from
the cluster.
Be careful about your data
Ensure to disable the Load Balancer before Decommissioning/Removing
a node. This is because there might be contention between the Master recovering
from the loss of the recently removed RegionServer and the running Load Balancer.
Hence, it important to stop the load balancer(if running)before removing the
regionserver from the cluster.
Also, in Apache HBase 0.90.2, there is an added facility for
having a node gradually shed its load and then shutdown itself down by using
the graceful_stop.sh script as follows:
$HBASE_HOME/bin/graceful_stop.sh HOSTNAME
where HOSTNAME is the host carrying the RegionServer you would
remove/decommission.
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