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Add Cassandra Scaler doc #452

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Add Cassandra Scaler doc #452

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Add Cassandra Scaler doc
nilayasiktoprak May 21, 2021
e9a0a19
Update content/docs/2.3/scalers/cassandra.md
nilayasiktoprak May 27, 2021
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88 changes: 88 additions & 0 deletions content/docs/2.3/scalers/cassandra.md
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title = "Cassandra"
availability = "v2.3+"
maintainer = "Community"
description = "Scale applications based on Cassandra query results."
layout = "scaler"
go_file = "cassandra_scaler"
+++

### Trigger Specification

This specification describes the `cassandra` trigger that scales based on the results of a Cassandra query result.

```yaml
triggers:
- type: cassandra
metadata:
username: "cassandra"
clusterIPAddress: "cassandra.default.svc.cluster.local:9042"
consistency: "Quorum" # Optional: If not set by the user the default value will be `gocql.One`.
protocolVersion: "4" # Optional: If not set by the user the default value will be `4`.
keyspace: "testing" # Optional: Used for generating the metricName.
query: "SELECT COUNT(*) FROM testing.test_table;"
targetQueryValue: "1"
metricName: "test_table-count" # Optional: If not set by the user the generated value would be `cassandra-<KEYSPACE>`, or if keyspace is not set either the default value would be just `cassandra`.
```

**Parameter list:**

- `username` - The username credential for connecting to the Cassandra instance.
- `clusterIPAddress` - The IP address or the host name of the Cassandra instance, with port number (optional).
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@zroubalik We had a scaler where we support full name and name + port separately, do you recall where we changed this? We might want to align here.

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I believe that it might be MSSQL scaler since the port is indicated as optional in the doc here: https://github.com/kedacore/keda-docs/blob/master/content/docs/2.3/scalers/mssql.md
So you mean that we should also support port as optional, right?

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I believe that it might be MSSQL scaler since the port is indicated as optional in the doc here: https://github.com/kedacore/keda-docs/blob/master/content/docs/2.3/scalers/mssql.md
So you mean that we should also support port as optional, right?

Is this right? @tomkerkhove

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I'd love to align this indeed, what do you think @zroubalik ?

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Yeah, I'd prefer to have the ability to specify the port in an optional field.

- `consistency` - Configuration for a session or per individual read operation.
- `protocolVersion` - CQL Binary Protocol.
- `keyspace` - The name of the keyspace used in Cassandra.
- `query` - A Cassandra query that should return single numeric value.
- `targetQueryValue` - The threshold value that is provided by the user and used as `targetAverageValue` in the Horizontal Pod Autoscaler (HPA).
- `metricName` - An optional name to assign to the metric. If not set KEDA will generate a name based on the `keyspace`. If using more than one trigger it is required that all metricNames be unique.

### Authentication Parameters

You can authenticate by using a password via `TriggerAuthentication` configuration.

**Password Authentication:**

- `password` - Password for configured user to login to the Cassandra instance.

### Example

```yaml
apiVersion: v1
kind: Secret
metadata:
name: cassandra-secrets
type: Opaque
data:
cassandra_password: CASSANDRA_PASSWORD
---
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
name: keda-trigger-auth-cassandra-secret
spec:
secretTargetRef:
- parameter: password
name: cassandra-secrets
key: cassandra_password
---
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
name: cassandra-scaledobject
spec:
scaleTargetRef:
name: example
triggers:
- type: cassandra
metadata:
username: "cassandra"
clusterIPAddress: "cassandra.default.svc.cluster.local:9042"
consistency: "Quorum"
protocolVersion: "4"
keyspace: "testing"
query: "SELECT COUNT(*) FROM testing.test_table;"
targetQueryValue: "1"
metricName: "test_table-count"
authenticationRef:
name: keda-trigger-auth-cassandra-secret
```