cki_tools.autoscaler

Autoscaler to scale replicas up and down

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

Configuration

Example:

.default:
  queue_prefix: amqp.exchange
  messages_per_replica: 20
  max_scale_up_step: 1
  max_scale_down_step: 1
  replicas_min: 1
  replicas_max: 5
  message_baseline: 0

app-name-1: {}

app-name-2:
  replicas_min: 2
  replicas_max: 20

YAML variable	Description
`queue_prefix`	Prefix to derive queue names from app names
`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.
`message_baseline`	Number of messages that should not be considered for scaling.

Ignoring the scaling steps, the target replica count is defined as

max(replicas_min,
  min(replicas_max,
    round_up(
      max(0, messages - messages_baseline) / messages_per_replica
    )
  )
)

Environment variable	Description
`CKI_DEPLOYMENT_ENVIRONMENT`	Define the deployment environment (production/staging)
`AUTOSCALER_CONFIG`	Configuration in YAML. If not present, falls back to `AUTOSCALER_CONFIG_PATH`.
`AUTOSCALER_CONFIG_PATH`	Path to the configuration YAML file
`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_DSN`	Sentry DSN