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README.md
bundle.yaml

README.md

Production-grade Docker Swarm Cluster

Overview

This is a core bundle for a Docker Swarm comprised of two major components with the following features:

  • Swarm (clustering engine)
    • Two node starter cluster, tested up to 20 nodes
    • TLS used for communication between nodes for security
    • ZFS used as a docker datastore for resiliance and performance
  • Consul (key-value and DNS)
    • Three node cluster for reliability

Usage

juju deploy swarm-consul

By default this will launch 2 swarm nodes, and 3 consul nodes. Either service can be scaled out post-deployment. The charms support workload status, so it is recommended to run watch juju status to monitor the cluster coming up. After it is deployed you need to grab the credentials from the lead swarm node to control the cluster:

juju scp swarm/0:swarm_credentials.tar .juju scp swarm/0:swarm_credentials.tar .
tar zxf swarm_credentials.tar
cd swarm_credentials
source enable.sh

This sets the proper environment variables to control the cluster, you can now check the state of the cluster:

docker status

And then run a hello-world to launch a container in the cluster, and then checking to ensure that the container is running on the remote cluster:

docker run hello-world
docker ps -a

List all networks in the cluster:

docker network ls

List all storage in the cluster:

docker storage ls

Scale out Usage

By default any docker container you run will automatically be spread throughout the number of swarm nodes you have deployed. We recommend no more than 30 docker containers per host if you are just using default constraints.

Scaling Swarm

To add more swarm nodes to host containers:

juju add-unit swarm

or specify machine constraints:

juju add-unit swarm --constraints "cpu-cores=8 mem=32G"

Refer to the machine constraints documentation for other machine constraints that might be useful for the swarm nodes.

Scaling Consul

Consul is used for service discovery, as a key-value store, and DNS resolution for the cluster. For reliability the cluster defaults to three instances out of the box.

For more scalability, we recommend bumping up to 5 total consul nodes per model. You can add more nodes with juju add-unit consul. The consul documentation recommends 3 to 5 nodes to strike a balance between availability and performance.

Known Limitations and Issues

The following issues still need to be resolved with this solution and are being worked on:

  • Killing the the swam master will result in loss of cluster PKI.
  • Consul nodes are not using TLS yet.
  • No easy way to find where the docker containers got deployed without sshing into each swarm node.
  • Add status to show which consul node is leader, and who are followers, just like swarm.
  • Consul isn't using ZFS.

Contact Information

Though this will be listed in the charm store itself don't assume a user will know that, so include that information here:

Upstream Project Name