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 targetValue or targetAverageValue (depending on the trigger metric type) in HPA. (This value can be a float)
• activationQueryValue - Target value for activating the scaler. Learn more about activation here.(Default: 0, Optional, This value can be a float)

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:

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

Or provide more detailed information:

• host - The host of the MySQL server.
• port - The port of the MySQL server.
• dbName - Name of the database.
• username - Username to authenticate with to MySQL database.
• passwordFromEnv - Password for the given user, this should be blank (no password) or point to an environment variable with the password.

Some parameters could be provided using environmental variables, instead of setting them directly in metadata. Here is a list of parameters you can use to retrieve values from environment variables:

• hostFromEnv - The host of the MySQL server, similar to host, but reads it from an environment variable on the scale target.
• portFromEnv - The port of the MySQL server, similar to port, but reads it from an environment variable on the scale target.
• usernameFromEnv - The username for connecting with host of the MySQL server, similar to username, but reads it from an environment variable on the scale target.

Authentication Parameters

You can authenticate by using connection string or password authentication.

Connection String Authentication:

• connectionString - Connection string for MySQL database.

Password Authentication:

• host - The host of the MySQL server.
• port - The port of the MySQL server.
• dbName - Name of the database.
• username - Username to authenticate with to MySQL database.
• password - 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:password@tcp(mysql:3306)/stats_db
---
apiVersion: keda.sh/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.sh/v1alpha1
kind: ScaledObject
metadata:
  name: mysql-scaledobject
  namespace: my-project
spec:
  scaleTargetRef:
    name: worker
  triggers:
  - type: mysql
    metadata:
      queryValue: "4.4"
      activationQueryValue: "5.4"
      query: "SELECT CEIL(COUNT(*) / 6) FROM task_instance WHERE state='running' OR state='queued'"
    authenticationRef:
      name: keda-trigger-auth-mysql-secret