camelr786 / caravan

epmd implementation and other OTP apps to make running Erlang/Elixir apps with Nomad and Consul easier.

Caravan

Tools for running Distributed Elixir/Erlang with Nomad and Consul

The built-in Erlang distribution mechanisms are prefaced on using the Erlang Port Mapper Daemon(EPMD), a process that is started with the VM and communicates with remote EPMD instances to determine what ports it's listening on. While this method can work in some cloud environments, cloud scheduling technologies such as Kubernetes or Nomad tend to make specific, random port assignments. Also, the built-in method for forming a cluster is to use a plaintext .hosts file with node names, which is very difficult to make work in a dynamic environment where node membership can change frequently.

There are several libraries and strategies for using the Kubernetes API to build a distributed cluster, but Consul provides us with a clean DNS api to retrieve information, and works with many different kinds of container schedulers (Nomad, Mesos, etc).

Caravan is split into two parts: The first is a set of modules that remove the need for epmd by determining node ports from the node name. The idea and much of the code is from the excellent article Erlang (and Elixir) distribution without epmd. It's worth the read, and should explain what we're trying to accomplish with the Caravan.Epmd module.

The second part utilizes libcluster to help with forming clusters automatically based on DNS SRV queries to Consul.

View extended documentation on Hex.

Installation

{:caravan, "~> 1.0.0"},