+++
title = "MySQL"
availability = "v1.2+"
maintainer = "Community"
description = "Scale applications based on MySQL query result."
go_file = "mysql_scaler"
+++

### 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](https://dev.mysql.com/doc/refman/8.4/en/comparison-operators.html#function_coalesce) 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`.

```yaml
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
```