The goal of this document is to give you enough technical specifics to configure and run the autoscaler. When properly configured, it will automatically provision and terminate Digital Ocean droplets based on your Drone server’s build volume.

Prerequisites

Create a Drone Token

You need to create a Drone user token with administrative privilege that you can provide to the autoscaler. The autoscaler will use this token to remotely access the Drone build queue. If you do not know how to create a token please see our tutorial.

Create a Digital Ocean Token

You need to create a Digital Ocean token that you can provide to the autoscaler. The autoscaler will use the token to authorize API requests.

Create an SSH Keypair

You need to create an ssh keypair named drone and add to Digital Ocean. The autoscaler uses the ssh key for remote login and access to your droplets.

Download

The autoscaler is distributed as a lightweight Docker image. The image is self-contained and does not have any external requirements.

docker pull drone/autoscaler

Start the Server

The autoscaler container can be started with the below command. The container is configured through environment variables. For a full list of configuration parameters, please see the configuration reference.

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docker run -d \
  -v /var/lib/autoscaler:/data \
  -e DRONE_POOL_MIN=${DRONE_POOL_MIN} \
  -e DRONE_POOL_MAX=${DRONE_POOL_MAX} \
  -e DRONE_SERVER_PROTO=${DRONE_SERVER_PROTO} \
  -e DRONE_SERVER_HOST=${DRONE_SERVER_HOST} \
  -e DRONE_SERVER_TOKEN=${DRONE_SERVER_TOKEN} \
  -e DRONE_AGENT_TOKEN=${DRONE_AGENT_TOKEN} \
  -e DRONE_DIGITALOCEAN_TOKEN=${DIGITAL_OCEAN_TOKEN} \
  -e DRONE_DIGITALOCEAN_SIZE=s-2vcpu-4gb \
  -p 8080:8080 \
  --restart=always \
  --name=autoscaler \
  drone/autoscaler

Reference

Environment

Configuration parameters are set using environment variables. This section defines a subset of recommended configuration parameters. For a full list, please see our configuration reference.

DRONE_DIGITALOCEAN_TOKEN

A string containing your Digital Ocean API token. It is used to authenticate requests to the Digital Ocean API.

DRONE_DIGITALOCEAN_TOKEN=m9yIGEgam9iPyBFbWFpbCBicmFkQGRyb25lL

DRONE_POOL_MIN

An integer defining the minimum number of droplets the autoscaler should keep alive. The default value is two droplets.

DRONE_POOL_MIN=2

DRONE_POOL_MAX

An integer defining the maximum number of droplets the autoscaler can provision. The default value is four droplets.

DRONE_POOL_MAX=4

DRONE_SERVER_PROTO

A string containing your Drone server protocol scheme. This value should be set to http or https.

DRONE_SERVER_PROTO=https

DRONE_SERVER_HOST

A string containing your Drone server hostname or IP address.

DRONE_SERVER_HOST=drone.domain.com

DRONE_SERVER_TOKEN

A string containing your Drone user token. This token must grant administrative access to your Drone server.

DRONE_SERVER_TOKEN=eyJhbGciOiJIUzI1NiIsInR5c...

DRONE_AGENT_TOKEN

A string containing the shared secret (DRONE_RPC_SECRET) that authorizes agent to server communication. This value is used to configure new agents.

DRONE_AGENT_TOKEN=IiOiIxMjM0NTY3ODkwIiwibmF...

Network

The autoscaler exposes REST endpoints so that you can extract runtime information from the system. The autoscaler listens on port 8080 inside the container, and should be published on the host machine:

--publish=8080:8080

Volumes

The autoscaler creates a sqlite database and persists to a contianer volume at /data. To prevent dataloss, we recommend mounting the data volume to the host machine.

--volume=/var/lib/autoscaler:/data