Azure Pipelines Scaler

Autoscale your Azure Pipelines Build Agents horizontally as needed

Getting started

Azure Pipelines Scaler (aps) uses a YAML file to specify which build queues on Azure Pipelines it should manage.

config:
  agent_dockerfile: ./agent
  poll_interval: 20
  pools:
    - pool: example
      image: ./config/definitions/example
      target_worker_count: "JOB_COUNT + 1"
azure_devops:
  pat: secret_here
  url: https://dev.azure.com/thomasgassmann

In the above example config the pool with the name example will be autoscaled. For each pool managed by aps an image and a target_worker_count have to be specified.

The image property is a path to a folder with a Dockerfile. This Dockerfile should contain the definition of how the build agent is going to look.

Important to notice is, that all images should have a debian base-image (apt-get is required).

aps will then build another image based on the image specified in image, add the build agent and start autoscaling the queue.

The target_worker_count property determines how many build agents the queue should have. This property supports maths expressions with predefined variables. Currently there are two predefined variables (JOB_COUNT and AGENT_COUNT). In the example above aps would autoscale the agent pool example to always have at least one more build agents than there are jobs in the queue.

Additionally a PAT (personal access token) and the URL to your Azure DevOps tenant have to be specified. The PAT needs to have access to build queues and builds in order to autoscale.

Before running aps, create a new directory containing the config.yml and a subdirectory definitions containing all images. Then run aps using the following command (adjust /path/config):

docker run
    --volume /var/run/docker.sock:/var/run/docker.sock \
    --volume /path/config:/app/config \
    thomasgassmann/aps:latest