Scaling Cluster Resources on EC2

If you have created your stack using the 3+ Cloud Formation template, you can temporarily add nodes and forests to scale up your cluster for periods of heavy use and then remove them later when less resources are needed.

Adding more hosts to a cluster is simple. Simply use the Update Stack feature to reapply the 3+ Cloud Formation template and provide a larger number for the NodesPerZone setting. Alternatively, you can add hosts by means of your Auto Scaling Groups. The recommended way to scale up the data capacity of your cluster is to add additional volumes, as described in Creating an EBS Volume and Attaching it to an Instance.

Scaling a cluster down involves some manual intervention:

1. Use MarkLogic and AWS tools to identify equal number of hosts in each ASG to delete. Never delete the host with the Security database, or any of the other built-in MarkLogic databases, such as Meters, App-Services, Modules, and so on.

2. Delete or move the data from the hosts to be removed to other hosts. This can be done by using the REST Management API or XQuery tieredstorage API to migrate partitions or forests to a volume on another host. For details on migrating data, see Migrating Forests and Partitions in Administrate MarkLogic Server.

3. As a super user, run the leave-cluster -terminate command on each host to be removed. This will cause the node to leave the cluster, and adjust the AutoScaling Group DesiredCount setting. For details, see leave-cluster.

4. Delete any unused volumes.

5. Update the Cloud Formation template to represent downsized cluster and use the Update Stack feature to reapply the template to the stack to alert AWS of the updated configuration.