Trigger Specification

This specification describes the postgresql trigger that scales based on a postgresql query

The Postgresql scaler allows for two connection options:

A user can offer a full connection string (often in the form of an environment variable secret)

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

Alternatively, a user can specify individual arguments (host, userName, password, etc.), and the scaler will form a connection string internally.

• host: - Service URL to postgresql. Note that you should use a full svc URL as KEDA will need to contact postgresql from a different namespace.
• userName: - Username for postgresql user.
• password: - Password for postgresql user.
• port - Postgresql port.
• dbName - Postgresql Database name.
• sslmode - SSL policy for communicating with database.

Finally, a user inserts a query that returns the desired value.

• query - What query to poll postgresql with. Query must return an integer.
• targetQueryValue - 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 PostgreSQL documentation for more information on the COALESCE function.

This is an example of using a full connection string:

triggers:
- type: postgresql
  metadata:
    connection: AIRFLOW_CONN_AIRFLOW_DB
    query: "SELECT ceil(COUNT(*)::decimal / 16) FROM task_instance WHERE state='running' OR state='queued';"
    targetQueryValue: 1

While this is an example of specifying each parameter:

triggers:
- type: postgresql
  metadata:
    userName: "kedaUser"
    password: PG_PASSWORD
    host: postgres-svc.namespace.cluster.local #use the cluster-wide namespace as KEDA
                                                #lives in a different namespace from your postgres
    port: "5432"
    dbName: postgresql
    sslmode: disable
    query: "SELECT ceil(COUNT(*)::decimal / 16) FROM task_instance WHERE state='running' OR state='queued';"
    targetQueryValue: 1

Authentication Parameters

You can authenticate by using a password or store the password within the connectionString.

Connection String Authentication:

• connection - Connection string for postgreSQL database.

Password Authentication:

• password - Password for configured user to login to postgreSQL database variables.

Example

apiVersion: keda.k8s.io/v1alpha1
kind: ScaledObject
metadata:
  name: airflow-worker
spec:
  scaleTargetRef:
    deploymentName: airflow-worker
  pollingInterval: 10   # Optional. Default: 30 seconds
  cooldownPeriod: 30    # Optional. Default: 300 seconds
  maxReplicaCount: 10   # Optional. Default: 100
  triggers:
    - type: postgresql
      metadata:
        connection: AIRFLOW_CONN_AIRFLOW_DB
        query: "SELECT ceil(COUNT(*)::decimal / 16) FROM task_instance WHERE state='running' OR state='queued';"
        targetQueryValue: 1