fly-autoscaler.yml

# The name of the target app that you want to scale.
app-name: "TARGET_APP_NAME"

# A list of regions to create machines in. Regions are chosen via round robin
# so that machines are evenly distributed.
# 
# If this is not specified, the autoscaler will choose a region based on the
# regions that the app is currently running in.
regions: ['iad', 'ord', 'sjc']

# This expression determines the number of machines to maintain in your app
# after each reconciliation. If the number of machines drops below this
# threshold then more will be created by cloning one of the existing machines.
# If the number of machines is above this threshold then some machines will be
# destroyed.
#
# There always needs to be at least one machine in your application so the 
# autoscaler will never destroy your last machine, even if the threshold reaches
# zero.
# 
# You can also define separate minimum & maximum thresholds using the
# "min_created_machine_count" & "max_created_machine_count" fields.
created-machine-count: "ceil(queue_depth / 10)"

# This expression determines the number of machines to maintain in a "started"
# state after each reconciliation. If the number of started machines is less
# existing machines will be started. If the number of started machines is more
# then running machines will be stopped.
#
# You can also define separate minimum & maximum thresholds using the
# "min_started_machine_count" & "max_started_machine_count" fields.
started-machine-count: "ceil(queue_depth / 10)"

# The frequency that the reconciliation loop will be run.
interval: "15s"

# A Fly.io auth token that has permission to start machines for the target app.
# This is typically set via the FAS_API_TOKEN environment variable.
api-token: "FlyV1 ..."

# If true, enables verbose debugging logging.
verbose: false

# Metric collectors fetch the current metrics when a reconciliation is performed.
#
# They store the current value locally with a given metric name so that the
# expression can be used to calculate the machine count.
metric-collectors:
  - type: "prometheus"
    metric-name: "queue_depth"
    address: "https://api.fly.io/prometheus/MY_ORG"
    query: "sum(queue_depth)"
    token: "FlyV1 ..."

  - type: "temporal"
    metric-name: "workflow_count"
    address: "localhost:7233"
    cert-data: "-----BEGIN CERTIFICATE-----..."
    key-data: "-----BEGIN EC PRIVATE KEY-----..."
    query: 'WorkflowType="my_workflow_type"'