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Scale applications based on Solace PubSub+ Event Broker Queues

Availability: 2.4+ Maintainer: Community

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Trigger Specification

This specification describes the solace-event-queue trigger that scales based on a Solace PubSub+ Event Broker queue.

- type: solace-event-queue
    solaceSempBaseURL:        http://solace_broker:8080
    messageVpn:               message-vpn
    queueName:                queue_name
    messageCountTarget:       '100'
    messageSpoolUsageTarget:  '100'       ### Megabytes (MB)
    username:                 semp-user
    password:                 semp-pwd
    usernameFromEnv:          ENV_VAR_USER
    passwordFromEnv:          ENV_VAR_PWD

Parameter list:

  • solaceSempBaseURL - Solace SEMP Endpoint in format: <protocol>://<host-or-service>:<port>.
  • messageVpn - Message VPN hosted on the Solace broker.
  • queueName - Message Queue to be monitored.
  • messageCountTarget - The target number of messages manageable by a pod. The scaler will cause the replicas to increase if the queue message backlog is greater than the target value per active replica.
  • messageSpoolUsageTarget - Integer value expressed in Megabytes (MB). The target spool usage manageable by a pod. The scaler will cause the replicas to increase if the queue spool usage is greater than the target value per active replica.
  • username - User account with access to Solace SEMP RESTful endpoint.
  • password - Password for the user account.
  • usernameFromEnv - Environment variable set with SEMP user account.
  • passwordFromEnv - Environment variable set with password for the user account.

Parameter Requirements:

  • Parameters resolving the target queue are all required: solaceSempBaseURL, messageVpn, queueName
  • At least one of messageCountTarget or messageSpoolUsageTarget is required. If both values are present, the metric value resulting in the higher desired replicas will be used. (Standard KEDA/HPA behavior)
  • The Solace PubSub+ Scaler polls the Solace SEMP REST API to monitor target queues. Currently, the scaler supports basic authentication. username and password are required for the solace-event-queue trigger to function. These values may be set directly in the trigger metadata or using a TriggerAuthentication record. See Authentication Parameters below. Alternatively, credentials may be passed from environment variables identified by usernameFromEnv and passwordFromEnv.

Authentication Parameters

You can use TriggerAuthentication CRD to configure the username and password to connect to the management endpoint.

Username and Password based authentication:

  • username - The username to use to connect to the Solace PubSub+ Event Broker’s SEMP endpoint.
  • password - The password to use to connect to the Solace PubSub+ Event Broker’s SEMP endpoint.


The objects in the example below are declared in namespace=solace. It is not required to do so. If you do define a namespace for the configuration objects, then they should all be delcared in the same namespace.

apiVersion: v1
kind: Secret
  name:      solace-secret
  namespace: solace
    app: solace-consumer
type: Opaque
  SEMP_USER:         YWRtaW4=
kind: ScaledObject
  name:      solace-scaled-object
  namespace: solace
    apiVersion:    apps/v1
    kind:          Deployment
    name:          solace-consumer
  pollingInterval: 20
  cooldownPeriod:  60
  minReplicaCount:  0
  maxReplicaCount: 10
  - type: solace-event-queue
      solaceSempBaseURL:       http://broker-pubsubplus.solace.svc.cluster.local:8080
      messageVpn:              test_vpn
      queueName:               SCALED_CONSUMER_QUEUE1
      messageCountTarget:      '50'
      messageSpoolUsageTarget: '100000'
      name: solace-trigger-auth
kind: TriggerAuthentication
  name: solace-trigger-auth
  namespace: solace
    - parameter:   username
      name:        solace-secret
      key:         SEMP_USER
    - parameter:   password
      name:        solace-secret
      key:         SEMP_PASSWORD

Currently available scalers for KEDA