Read replicas

This section will describe how to create a universe with both a primary and read replica cluster in a hybrid cloud deployment, as well as dynamically add, edit, and remove, a read replica cluster. In this example, we are first going to deploy a universe with primary cluster in Oregon (US-West) and read replica cluster in Northern Virginia (US-East).

Create the universe

First, we are going to enter the following values to create a primary cluster on GCP cloud provider. Click Create Universe and then enter the following intent.

• Enter a universe name: helloworld3
• Enter the set of regions: Oregon
• Enter the replication factor: 3
• Change instance type: n1-standard-8
• Add the following GFlag for Master and T-Server: leader_failure_max_missed_heartbeat_periods = 10. Since the the data is globally replicated, RPC latencies are higher. We use this flag to increase the failure detection interval in such a higher RPC latency deployment.

Then, click Configure Read Replica and then enter the following intent to create a read replicacluster on AWS.

• Enter the set of regions: US East
• Enter the replication factor: 3
• Change the instance type: c4.large

Since we do not need to a establish a quorum for read replica clusters, the replication factor can beeither even or odd. Click Create.

Examine the universe

While waiting for the universe to get created, it should look like this:

Once the universe is created, you should see something like this in the universe overview.

Note how we have a distinguished primary and read replica cluster defined, designated by the yellow and green groups respectively.

Universe nodes

You can browse to the Nodes tab of the universe to see a list of nodes. Note that the nodes are grouped by primary or read replica, and read replica nodes have a readonly1 identifier associated with the name.

Go to the cloud providers’ instances page. In GCP, browse to Compute Engine->VM Instances and search for instances that have helloworld3 in their name. You should see something as follows, corresponding to our primary cluster.

In AWS, browse to Instances and do the same search, you should see 3 nodes corresponding to our readreplica cluster.

We have successfully created a hybrid cloud deployment with the primary cluster in GCPand the read replica cluster in AWS!

Add, remove, edit a read replica cluster

In this section, we cover dynamically adding, editing, and removing a read replica cluster from anexisting universe. Let’s create a new universe helloworld4 with a primary cluster exactly as helloworld3 but without anyread replica cluster. Click Create and wait for the universe to be ready. Once this is done,navigate to the Overview tab, and find the More dropdown in the top right corner. There you shouldfind a Configure Read Replica selection - click on that.

You will see a page to configure the read replica cluster. Enter the same intent we used for theread replica cluster in helloworld3 and click Add Read Replica.

Once this is done, go to the Nodes tab and verify that you have 3 new read replica nodes all in AWS.To edit our read replica cluster, we go back to the More dropdown and select Configure Read Replica. Add anode to the cluster (it will automatically select a Availability Zone to select from) and click onEdit Read Replica.

Once the universe is ready, go to the Nodes tab and you can see the new read replica node for atotal of 4 new nodes.

Finally, to delete the read replica cluster, go back to the Configure Read Replica page and click Deletethis configuration. You will be prompted to enter the universe name for safety purposes. Do this andpress Yes.

Once this is done, go back to the Nodes page and verify that you only see the 3 primary nodes fromour initial universe creation. You have dynamically added, edited, and removed a read replicacluster from an existing universe.