# Control Node


🚀 **Continuous Delivery and Orchestration as code for Elixir**

## Installation

def deps do
    {:control_node, "~> 0.2.0"}

## TL;DR

`control_node` is an Elixir library which offers APIs that allow you to build
your own deployment and orchestration workflows. For a given a release tar of an
Elixir/Erlang project `control_node` offers APIs to store and manage release tar
via local registry and also deploy these release tar to remote hosts (via SSH) and
monitor service nodes.

## Pre-requisites

In order to use `control_node` you must ensure the following,

- You are deploying to virtual machines or bare metal servers. Control node
  should have SSH access all these host machines where the releases will run.
- Your Erlang/Elixir project when started should run the EPMD (it runs by
  default if you don't change the config)

## Features

- [x] Support multiple namespaces for a release
- [x] Rollout releases to hosts via SSH
- [x] Native node monitoring and restart on failover
- [x] Dynamically scale up/down your release instances
- [x] Native service monitoring/health check
- [x] Blue-Green deployment
- [ ] Support namespace environment variable configuration
- [ ] Hot upgrade your release config
- [ ] Rollback releases

## Quick example

This library ships with an example `service_app` under `example/` folder. You can try out this library
by trying to deploy the release using the following steps,

Clone the repo
$ git clone
$ cd control-code/

Start an SSH server locally where the release will be deployed,
$ docker-compose up -d

Start `iex` with distribution turned on
$ iex -S mix
Erlang/OTP 23 [erts-11.0] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Interactive Elixir (1.10.4) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> :net_kernel.start([:control_node_test, :shortnames])

Execute the Elixir code snippets in the console,

- Define `ServiceApp` module (copy paste the code in the console) which will offer
API to deploy `service_app`,
defmodule ServiceApp do
  use ControlNode.Release,
    spec: %ControlNode.Release.Spec{name: :service_app, base_path: "/app/service_app"}

- Declare a `host_spec` which will hold the details of which host the release can be deployed to
host_spec = %ControlNode.Host.SSH{
  host: "localhost",
  port: 2222,
  user: "",
  private_key_dir: Path.join([File.cwd!(), "test/fixture", "host-vm/.ssh"])

- Declare a `namespace_spec` which define the namespace for a given release. Notice that the
namespace allows specifying a list of `hosts` and `registry`.
A registry module offers API to retrieve the release tar and here we use a `Local` registry
which will retrieve the release tar from the filesystem.

namespace_spec = %ControlNode.Namespace.Spec{
  tag: :testing,
  hosts: [host_spec],
  registry_spec: %ControlNode.Registry.Local{path: Path.join(File.cwd!(), "example")},
  deployment_type: :incremental_replace,

- Now we deploy the release to a given `namespace_spec` i.e. the release we be started on on
all the `hosts` specified in the namespace. Notice that once the deployment is finished
`control_node_test@hostname` automatically connects to release nodes,

iex(control_node_test@hostname)5> ServiceApp.start_link(namespace_spec)
iex(control_node_test@hostname)6> ServiceApp.deploy(:testing, "0.1.0")
iex(control_node_test@hostname)7> Node.list()

### SSH server config to enable tunneling
In order to ensure that Control Node can connect to release node the SSH servers running
the release should allow tunneling,

AllowTcpForwarding yes

## Limitation

- **SSH client only supports `ed25519` keys**
- Only short names for nodes are allowed ie. `sevice_app@hostname` is support and **not** ``
- Nodes of a given release (deployed to different) should have different
  hostname for eg. if node 1 has node name `service_app@host1` then another node
  of `service_app` should have a different node name.