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question

nagasree963_193876 avatar image
nagasree963_193876 asked ·

Does the cass-operator support on demand scale up of read replicas?

Did cass-operator supports on demand scale up of read replicas. Operator version:1.3 and application version:3.11.6.

cass-operator
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1 Answer

Erick Ramirez avatar image
Erick Ramirez answered ·

There are several points I need to cover because your questions seem to cover the same subject. You just ask the same question differently but the answer is the same.

Replicas

As I explained in your previous question (#6523), "read replicas" and "write replicas" are one and the same. No one uses those phrases in Cassandra -- they are just replicas.

I also mentioned in that post that you're asking about Cassandra concepts one tiny bit at a time. If you at the very least watch the videos in the DS201 Cassandra Foundations course, you will save yourself a lot of time. Help me help you -- do the course. :)

Auto-scaling

Automatically adding or decommissioning nodes is never a good idea with Cassandra because it is an expensive operation. Bootstrap and streaming operations take a long time depending on how much data each node owns. Once the bootstrap or decommission process has started, it can't be interrupted without consequences.

For the same reason, the cass-operator does not support on-demand scaling. John Sanda has covered this briefly in his response to your other question (#6528). This is effectively the same question so the answer is the same.

Scaling up a DC

It is possible to manually scale up the number of nodes in a DC using the cass-operator.

The size parameter of the CassandraDatacenter determines how many nodes are deployed in a DC. Here's an example configuration of a DC called dc1 with size: 3 nodes:

kind: CassandraDatacenter
metadata:
  name: dc1
spec:
  clusterName: cluster1
  serverType: cassandra
  serverVersion: 3.11.6
  size: 3
  ...

To scale up the number of nodes, you will need to edit your YAML configuration and re-apply it with the kubectl command. The pod(s) will be added to the DC provided there are enough Kubernetes worker nodes in your Kubernetes cluster. For details, see Scaling up a datacenter.

Note that scaling down is not supported as documented in the cass-operator release notes. Cheers!

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okay. one more doubt, Did cass-Operator supports HA design using Logical/Physical Replication Leverage DB solutions like Patroni etc.

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Your follow up question is again asking the same thing in your various other posts, but you're just asking it differently. I really recommend you at least watch some of the videos in the DS201 Cassandra Foundations course at the DataStax Academy so we're not going over the same questions over and over. Cheers!

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