You can apply all optional parameters to an existing service instance using the cf update-service command. You can, for example, scale up a cluster by increasing the number of servers.

Previously specified optional parameters are persisted through subsequent updates. To return the service instance to default values, you must explicitly specify the defaults as optional parameters.

For example, if you create a service instance with five servers using a plan that has a default value of four servers:

$ cf create-service p-cloudcache small my-cloudcache -c '{"num_servers": 5}'

And you set the new_size_percentage to 50%:

$ cf update-service my-cloudcache -c '{"new_size_percentage": 50}'

Then the resulting service instance has 5 servers and new_size_percentage of 50% of heap.

Rebalancing a Cluster

When updating a cluster to increase the number of servers, the available heap size is increased. When this happens, VMware Tanzu GemFire for VMs automatically rebalances data in the cache to distribute data across the cluster.

This automatic rebalancing does not occur when a server leaves the cluster and later rejoins, for example when a VM is re-created, or network connectivity is lost and restored. In this case, you must manually rebalance the cluster using the gfsh rebalance command while connected to the cluster under a role that can manage a cluster's data.

Note: You must first connect with gfsh over HTTPS before you can use the rebalance command. For more information, see Connect with gfsh over HTTPS in Accessing a Service Instance.

By default, the server rebalances based on the size of data in each member hosting the region. You can change the algorithm to specify rebalancing based, instead, on bucket count, by specifying the pr_load_probe_class parameter in the cf create-service command. Be aware that changing the rebalancing algorithm is a data-intensive operation and can affect performance while the change is taking place.

Restarting a Cluster

Restarting a cluster stops and restarts each cluster member in turn, issuing a rebalance as each restarted server joins the cluster.

WARNING: Restart of a cluster may cause data loss.

There is a potential for data loss when restarting a cluster; the region type and number of servers in the cluster determine whether or not data is lost.

  • All data is lost when restarting a cluster with these region types and number of servers:

    • Partitioned regions without redundancy or persistence. As each server is stopped, the region entries hosted in buckets on that stopped server are permanently lost.
    • Replicated regions without persistence on a cluster that has a single server.
    • A Colocated Single-VM Plan cluster loses all data, as there is a single server and no region persistence.
  • No data is lost when restarting the cluster with these region types and number of servers:

    • Replicated regions for clusters with more than one server.
    • Persistent regions will not lose data, as all data is on the disk and available upon restart of a server.
    • Partitioned regions with redundancy. When the server with the primary copy of an entry is stopped, the redundant copy still exists on a running server.

To restart a cluster, use the VMware Tanzu Application Service for VMs (TAS for VMs) operator credentials to run the command:

cf update-service SERVICE-INSTANCE-NAME -c '{"restart": true}'

For example:

$ cf update-service my-cluster -c '{"restart": true}'

Adding a Service Gateway

A service gateway may be added to a service instance that has TLS connections enabled. Use the command

cf update-service SERVICE-INSTANCE-NAME -c '{"service_gateway":true, "tls":true}

where SERVICE-INSTANCE-NAME is the name assigned to the service instance upon creation.

Changes to the Service Plan

Your TAS for VMs operator can change details of the service plan available on the Marketplace. If your operator changes the default value of one of the optional parameters, this does not affect existing service instances.

However, if your operator changes the allowed values of one of the optional parameters, existing instances that exceed the new limits are not affected, but any subsequent service updates that change the optional parameter must adhere to the new limits.

For example, if the TAS for VMs operator changes the plan by decreasing the maximum value for num_servers, any future service updates must adhere to the new num_servers value limit.

You might see the following error message when attempting to update a service instance:

$ cf update-service  my-cloudcache -c '{"num_servers": 5}'
Updating service instance my-cloudcache as admin...
Server error, status code: 502, error code: 10001, message:
Service broker error: Service cannot be updated at this time,
please try again later or contact your operator for more information

This error message indicates that the operator has made an update to the plan used by this service instance. You must wait for the operator to apply plan changes to all service instances before you can make further service instance updates.

Changes to Advanced Configuration

Advanced configuration allows users to configure custom JVM options, GemFire properties, credentials, and Resource Manager properties. This property is not recommended for general use. Do not attempt to modify a service instance's advanced configuration unless you are support staff or an experienced user with knowledge of the existing configuration. See Advanced Service Instance Configuration for details.

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