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docker-swarm-autoscaler

Current Release: 0.1.0

This project is intended to bring auto service staling to Docker Swarm. This script uses prometheus paired with cadvisor metrics to determine cpu usage. It then uses a manager node to determine if a service wants to be autoscaled and uses a manager node to scale the service.

Currently the project only uses cpu to autoscale. If cpu usage reaches 85% the service will scale up, if it reaches 25% it will scale down.

Usage

  1. You can deploy prometheus, cadvisor, and docker-swarm-autoscaler by running docker stack deploy -c swarm-autoscaler-stack.yml autoscaler from the root of this repo.
  • You can also utilize an already deploy prometheus and cadvisor by specifying the PROMETHEUS_URL in docker-swarm-autoscaler environment. swarm-autoscaler-stack.yml shows an example of this.
  • docker-swarm-autoscale needs a placement contstraint to deploy to a manager. swarm-autoscaler-stack.yml shows an example of this.
  1. For services you want to autoscale you will need a deploy label swarm.autoscaler=true.
deploy:
  labels:
    - "swarm.autoscaler=true"

This is best paired with resource constraints limits. This is also under the deploy key.

deploy:
  resources:
    reservations:
      cpus: '0.25'
      memory: 512M
    limits:
      cpus: '0.50'

Configuration

Setting Value Description
swarm.autoscaler true Required. This enables autoscaling for a service. Anything other than true will not enable it
swarm.autoscaler.minimum Integer Optional. This is the minimum number of replicas wanted for a service. The autoscaler will not downscale below this number
swarm.autoscaler.maximum Integer Optional. This is the maximum number of replicas wanted for a service. The autoscaler will not scale up past this number

Test

You can deploy a test app with the following commands below. Helloworld is initially only 1 replica. The autoscaler will scale to the minimum 3 replicas.

  1. docker stack deploy -c swarm-autoscaler-stack.yml autoscaler
  2. docker stack deploy -c helloworld.yml hello