This projects provides a distributed, reliable key-value store setup used for service-discovery within a docker swarm environment.

In a docker swarm environment there is no way to control the startup order of nodes withing the swarm. As some services need to be deployed redundant in a master/slave setup a mechanism is needed to control the lifecycle of services within the swarm.

My docker-cluster-controller project provides a python class to manage this service lifecycle from within a docker-entrypoint script.

However a central key-value store is required to store an instances properties like its role in a cluster. This project provides the Dockerfile to create a etcd image and a compose file which can be used to start a etcd cluster.

The image can be build using docker build -t etcd . and needs some environment variable's set to operate:

To start a cluster a so called bootstrap node is needed. This node is only required during the startup of the cluster.

The swarm has two networks: sd_backend and sd_frontend. The backend network is used for communication between the ETCD nodes and the bootstrap node. The frontend network can be used to have other containers connect to the ETCD cluster.

docker build -t etcd .
docker stack deploy -c docker-swarm.yml etcd-cluster

Check the cluster:

docker stack ps etcd-cluster

Check the logs:

docker service logs etcd-cluster_bootstrap-service-discovery
docker service logs etcd-cluster_service-discovery