Replacing a Node
At some point, for various reasons, you might need to replace a node in your Riak cluster (which is different from recovering a failed node). Here is the recommended way to go about replacing a node.
Back up your data directory on the node in question. In this example scenario, we’ll call the node
sudo tar -czf riak_backup.tar.gz /var/lib/riak /etc/riak
If you have any unforeseen issues at any point in the node replacement process, you can restore the node’s data from this backup.
Download and install Riak on the new node you wish to bring into the cluster and have it replace the
riak4node. We’ll call the new node
riak7for the purpose of this example.
Start the new
Plan the join of the new
riak7node to an existing node already participating in the cluster; for example
riak-admin cluster joincommand executed on the new
riak-admin cluster join riak0
Plan the replacement of the existing
riak4node with the new
riak7node using the
riak-admin cluster replacecommand:
riak-admin cluster replace riak4 riak7Single NodesIf a node is started singly using default settings (as, for example, you might do when you are building your first test environment), you will need to remove the ring files from the data directory after you edit `/etc/vm.args`. `riak-admin cluster replace` will not work as the node has not been joined to a cluster.
Examine the proposed cluster changes with the
riak-admin cluster plancommand executed on the new
riak-admin cluster plan
If the changes are correct, you can commit them with the
riak-admin cluster commitcommand:
riak-admin cluster commit
If you need to clear the proposed plan and start over, use
riak-admin cluster clear:
riak-admin cluster clear
Once you have successfully replaced the node, it should begin leaving
the cluster. You can check on ring readiness after replacing the node
You’ll need to make sure that no other ring changes occur between the time when you start the new node and the ring settles with the new IP info.
The ring is considered settled when the new node reports
true when you run
riak-admin ringready command.