cki.deployment_tools.autoscaler

Autoscaler to scale replicas up and down

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Dynamically scale up and down the replicas of a DeploymentConfig depending on the number of messages in the queue it’s consuming.

Configuration

This script reads the configuration from the AUTOSCALER_CONFIG environment variable, with the following content:

{
    ".default": {
        "namespace": "namespace-name",
        "messages_per_replica": 20,
        "max_scale_up_step": 1,
        "max_scale_down_step": 1,
        "replicas_min": 1,
        "replicas_max": 5
    },
    "app-name-1": {
        "deployment_config": "dc-app-1",
        "queue": "queue-app-1"
    },
    "app-name-2": {
        "deployment_config": "dc-app-2",
        "queue": "queue-app-2",
        "replicas_min": 2,
        "replicas_max": 20
    }
}

If AUTOSCALER_CONFIG is not present, it will try to load the config from the --config path, in YAML format.

---
.default:
  namespace: namespace-name
  messages_per_replica: 20
  max_scale_up_step: 1
  max_scale_down_step: 1
  replicas_min: 1
  replicas_max: 5

app-name-1:
  deployment_config: dc-name-1
  queue: queue-name-1

app-name-2:
  deployment_config: dc-name-2
  queue: queue-name-2
  replicas_min: 2
  replicas_max: 20

Each application needs to be configured with the corresponding deployment-config and queue values. Default values can be overriden on the application section.

Yaml variable	Description
`namespace`	Openshift namespace.
`messages_per_replica`	Number of messages a replica can handle before scaling up.
`max_scale_up_step`	Maximum number of replicas that can be spawned on a single refresh period.
`max_scale_down_step`	Maximum number of replicas that can be deleted on a single refresh period.
`replicas_min`	Minumum number of replicas spawned at the same time.
`replicas_max`	Maximum number of replicas spawned at the same time.
`deployment_config`	Name of the OpenShift DeploymentConfig.
`queue`	Name of the RabbitMQ queue.

Environment variable	Description
`CKI_DEPLOYMENT_ENVIRONMENT`	Define the deployment environment (production/staging)
`AUTOSCALER_CONFIG`	Configuration in JSON. If not present, falls back to `AUTOSCALER_CONFIG_PATH`.
`AUTOSCALER_CONFIG_PATH`	Path to the configuration YAML file (Default: config.yaml)
`REFRESH_PERIOD`	Time in seconds between checks (Default: 30).
`RABBITMQ_HOST`	RabbitMQ host
`RABBITMQ_PORT`	RabbitMQ port, TLS is used for port 443
`RABBITMQ_USER`	RabbitMQ user
`RABBITMQ_PASSWORD`	RabbitMQ password
`RABBITMQ_CAFILE`	RabbitMQ CA file path
`RABBITMQ_CERTFILE`	RabbitMQ certificate + private key file path
`SENTRY_SDN`	Sentry SDN

CKI_DEPLOYMENT_ENVIRONMENT

On staging developments (CKI_DEPLOYMENT_ENVIRONMENT != production), the changes are only logged but not applied.