Trigger Specification

This specification describes the mysql trigger that scales based on result of MySQL query.

The trigger always requires the following information:

• query - A MySQL query that should return single numeric value.
• queryValue - A threshold that is used as targetAverageValue in HPA.

Note that the query must return a single integer value. If the query has a possibility of returning null, a default value can be set using the COALESCE function. For example, SELECT COALESCE(column_name, 0) FROM table_name;. See MySQL documentation for more information on the COALESCE function.

To provide information about how to connect to MySQL you can provide:

• connectionString - MySQL connection string that should point to environment variable with valid value.

Or provide more detailed information:

• username - Used to access MySQL database.
• password - Used for the given user, this should be blank (no password) or point to an environment variable with the password.
• host - Host of the database.
• port - Port of the database.
• dbName - As name of the database.

Authentication Parameters

You can authenticate by using connection string or password authentication.

Connection String Authentication:

• connection - Connection string for MySQL database.

Password Authentication:

• connection - Password for configured user to login to MySQL database variables.

Example

Here is an example of how to deploy a scaled object with the mysql scale trigger which uses TriggerAuthentication.

apiVersion: v1
kind: Secret
metadata:
  name: mysql-secrets
  namespace: my-project
type: Opaque
data:
  mysql_conn_str: dXNlckB0Y3AobXlzcWw6MzMwNikvc3RhdHNfZGI= # base64 encoded value of mysql connectionString of format user@tcp(mysql:3306)/stats_db
---
apiVersion: keda.k8s.io/v1alpha1
kind: TriggerAuthentication
metadata:
  name: keda-trigger-auth-mysql-secret
  namespace: my-project
spec:
  secretTargetRef:
  - parameter: connectionString
    name: mysql-secrets
    key: mysql_conn_str
---
apiVersion: keda.k8s.io/v1alpha1
kind: ScaledObject
metadata:
  name: mysql-scaledobject
  namespace: my-project
spec:
  scaleTargetRef:
    deploymentName: worker
  triggers:
  - type: mysql
    metadata:
      queryValue: "4"
      query: "SELECT CEIL(COUNT(*) / 6) FROM task_instance WHERE state='running' OR state='queued'"
    authenticationRef:
      name: keda-trigger-auth-mysql-secret