How to configure autoscaling on docker swarm? - Stack Overflow

Short answer: There is no easy way to do this with Docker Swarm for now.

Docker Swarm (or Swarm mode) does not support auto-scalingmachines out of the box. You'd need to use another solution for that like docker-machineto create machines (with docker) on your infrastructure and link these to the existing Swarm cluster (with docker swarm join).

This will involve a lot of scripting but the idea is to monitor the cluster for CPU / Memory / Network usage (with topor monit) and once it goes beyond a threshold (say 70%of total cluster resources), you trigger a script calling docker-machineto scale up the cluster. Using the same idea you can also scale down by drainingand removingnodes (preferably Agentnodes) from the existing swarm cluster once your are below the lower threshold.

You need to make sure you are monitoring for sustained resource usage if you want to use this criteria or you will have your Infrastructure spawning and destroying nodes from the frequent and sudden changes in resource usage.

You can define a lower bound and an upper bound for machines in the cluster to keep things under control.

Note that Swarm requires at least 3 Managernodes (recommended 5) to maintain a quorum for the Distributed Consensus algorithm. So the minimum recommended lower bound is 5 nodes(which you can extend with Agentnodes as resources are incrementally being used by services).

To some extent, you can also take a look at Docker InfraKitor Terraformfor Infrastructure automationand Health monitoring.

Update: There is now a promising cross-platform autoscaler that supports Swarm Mode task auto-scaling: Orbiter. Although still nothing out-of-the-box yet for service/machine autoscaling.