jdiamond / controller

Longshoreman controller application.

Longshoreman Controller

The controller manages the application container cluster. It works with one or more routers to create a highly available and redundant cluster for Docker-based applications.

The controller exposes a number of utility API endpoints that can be used to manage the cluster state using the CLI tool.

Lingo

Hosts

A host is a single node's IP. Multiple application instances can be deployed on a single host. When deploying a new application instance, hosts with the least utilization are selected for deployment. Hosts can be added or removed from the cluster at any time.

Apps

An App is represented by a domain name and a set of environmental variables. App instances are deployed to multiple hosts. Ports are dynamically assigned and propagated to the routers. Longshoreman applications must include an EXPOSE 3000 port as the external to internal port mapping is currently not configurable. This will change shortly.

Instances

Application instances are deployed to hosts using the built in Docker Remote API.

Envs

Each application can be configured using environmental variables. Variables can be set at any time and will trigger a restart.

Router

Traffic is routed to application components via the routers. Routers are applications which dynamically HTTP requests to the appropriate back-end instances. Routers are notified of updates to the routing table using Redis PubSub.

Endpoints

These endpoints are utilized by the CLI tool.

GET /apps

Load the currently configured applications.

GET /hosts

Load the IPs of all hosts in the cluster.

POST /hosts

Add a new host to the cluster.

DELETE /hosts/:host

Remove a host from the cluster.

POST /:app/deploy => '{"image": "docker/image"}'

Deploy an application to the cluster. Specify a Docker image name.

GET /:app/instances

Return all instances for an application.

GET /:app/envs

Get all environmental variables for an application.

POST /:app/envs

Add a new environmental variables to an application.

DELETE /:app/envs/:env

Remove an environmental variables from an application.

Start a Controller

Just run sudo docker.io run -e REDIS_HOST=$REDIS_HOST_IP -e REDIS_PORT=6379 longshoreman/controller on your controller node(s) to start directing traffic to your Docker application instances. $REDIS_HOST_IP is the IP address of your Redis database.

TODO

• Better error handling for failed image downloads

• Storing revisions for application state will allow for simple rollback. However, rollbacks can still be achieved by deploying a specific Docker image tag.

• Smarter handling of host removal and addition. The controller should redistribute application instances across the cluster based on available resources.

• etcd support to eliminate single points of failure. Currently uses Redis.