Minex

A deployment helper for Elixir.

Minex has no strong opinion on how you should do your deployments. It has no deployment strategies, but allows you to define them youself with a simple syntax. It does provide helpers to easily run commands. Both locally and over SSH (in a single session where possible).

Local commands are run with an interactive shell by default (using Erlexec). Remote commands are run as ssh commands.

Installation

Add to your mix.exs and run mix deps.get:

def deps do
  [
    {:minex, "~> 0.1.0", only: :dev}
  ]
end

Get started by running:

mix minex.init

This will create the following files:

• config/deploy.exs
• config/deploy/tasks.exs

Get Started

The initial deploy.exs contains a basic sample of how a deployment can work. You define tasks that can execute commands locally or on a remote server.

Example deploy file:

use Minex

set(:name, "my_app")
set(:deploy_to, "/apps/#{get(:name)}")
set(:host, "[email protected]")

Code.require_file("deploy/tasks.exs", Path.dirname(__ENV__.file))

# expects a config/deploy/Dockerfile
public_task(:build, fn ->
  command("docker container rm dummy", allow_fail: true)
  command("docker build -f config/deploy/Dockerfile  -t #{get(:name)} .")
  command("docker create -ti --name dummy #{get(:name)}:latest bash")
  command("docker cp dummy:/release.tar.gz release.tar.gz")
end)

public_task(:deploy, fn ->
  run(:build)
  run(:upload, ["release.tar.gz", "#{get(:deploy_to)}/release.tar.gz"])
  run(:remote, fn ->
    command("cd #{get(:deploy_to)}")
    command("( [ -d \"bin\" ] && ./bin/#{get(:name)} stop || true )")
    command("tar -zxf release.tar.gz -C .")
    command("./bin/#{get(:name)} daemon")
  end)
end)

Minex.run(System.argv())

A public task can be run with mix minex task_name, for example:

mix minex deploy

Tip: in your mix.exs you can add aliases for your most used commands. You can for example add deploy: ["minex deploy"] and then deploy with mix deploy.

Basics

Tasks and commands

A normal task can only be run internally and not from the command line.

task(:my_task, fn ->
  command("echo a")
  command("echo b")
  command("echo c")
end)

By default a command is run from the local shell. Only if it's included in a :remote block, the nested commands will be run over SSH remotely.

run(:remote, fn ->
  run(:my_task)
end)

The code above will result in the following command being executed:

ssh [email protected] -- $'( echo a && echo b && echo c )'

If a command results in a non-zero exit code, the rest of the script is aborted (both locally and remotely).

Tasks can accept arguments if needed:

task(:my_task, fn [arg] ->
  command("echo #{arg}")
end)

run(:my_task, ["test"])

Minex defines some base tasks:

Public tasks:

• :help - public task to display the help message (list available public tasks). This is als triggered if you run minex without arguments.
• :generate_script - public task to generate a bash script for the tasks defined with generate_script_task.

Helper tasks:

• :command - this task is triggered for each command() you call. Can execute locally or remotely, depending on the context.
• :remote - collect all nested commands and execute them on the :host over SSH by chaining them.
• :upload - takes a [local_path, remote_path] as argument and uses :scp to upload the file to the :host
• :download - takes a [remote_path, local_path] as argument and uses :scp to download the file from the :host
• :scp - takes a [source, dest], so this should include the host. Used by upload and download internally.

And some internal commands:

• :remote_command - run a single command remotely. Used internally by the :remote task.
• :local_command - run a single command locally. Used internally if not in remote mode. This will raise on non-zero exit codes.
• :remote_exec - core task to run a command over SSH. this actually triggers a local command that executes ssh from the shell.
• :local_exec - core task to run a command locally (uses Erlexec)

Settings

These settings wills be used by the base tasks:

• :host - target server for remote tasks
• :ssh_opts - string with options for the ssh command line call
• :scp_opts - string with options for the scp command line call
• :remote_command_options - keyword list of commands options the executing the ssh commands locally. Default is []
• :local_command_options - keyword list of basic commands options for all local commands. Default is [interact: true, echo_cmd: true]
• :generate_script_template - EEx template that renders the bash script for the generate_script command.

Other settings can be defined at will for your own use.

Advanced usage

Multiple environments

A common usecase is having multiple environments like staging and production.

A way to support that is by first specifying the environment before you execute a task.

use Minex

# ...

args =
  case System.argv() do
    ["staging" | args] ->
      set(:host, "your_staging_host")
      args

    ["production" | args] ->
      set(:host, "your_production_host")
      args

    [_other | _] ->
      raise "please supply an environment as the first argument"

    [] ->
      # allow empty to display help
      []
  end

# Run with the rest of the args
Minex.run(args)

Build on a seperate build server

If you want to run your commands on a seperate build server, you can either change your host to the build server and change it back to the target server later or you can create a specific task to temporarily change the settings:

task(:build_server, fn [fun] ->
  # set always returns the old settings of the keys you set
  previous_settings =
    set(
      host: get(:build_server_host),
      ssh_opts: "-i ~/.ssh/build_key"
    )

  run(:remote, fn ->
    fun.()
  end)

  # reset
  set(previous_settings)
end)

run(:build_server, fn ->
  # ...
end)

Use a single SSH connection

To re-use the same connection you can set up a control master. You can do this by specifiying it in your ~/.ssh/config or by starting it in the task:

# Build in settings that are used in the scp/ssh task
set(:ssh_opts, ~s[-o ControlPath=".ssh-control.%h"])
set(:scp_opts, ~s[-o ControlPath=".ssh-control.%h"])

# Start SSH connection in master mode and detach the first time data is received
task(:start_ssh, fn ->
  command("ssh #{get(:ssh_opts)} -TM #{get(:host)}", on_receive: fn _, _ -> :detach end, interact: false)
end)

task(:deploy, fn ->
  run(:build)

  run(:start_ssh)

  # ...
end)

Overriding tasks

It's possible to override the build-in (or your own) tasks:

task(:remote_exec, [override: true], fn [command, options] ->
  # your own implementation
end)

Generate script tasks

The generate_script_task creates tasks that will be exported to a bash script. This is because for some tasks (like a remote console) you need a full shell/pty and this is not easy to start from the beam.

generate_script_task(:iex, fn ->
  run(:remote, fn ->
    command("cd #{get(:deploy_to)} && ./bin/#{get(:name)} remote")
  end)
end)

Generate the bash script to a file of your choosing:

mix minex generate_script my_script

./my_script iex

If you have multiple environments configured:

mix minex production generate_script script/production
mix minex staging generate_script script/staging

./script/production iex

Note: to create both public and generate_script tasks, you can define them like this:

public_task(:name, [generate_script: true], fn ->
  #...
end)

Use a PTY

Some (interactive) commands need a PTY to be present. The enable this:

set(:remote_command_options, [pty: true])
set(:ssh_opts, "-t")

Entering passwords

Entering passwords works, but they will be visible in the terminal. The easiest way around this would be generate_script tasks and then actually executing the script from the shell.

The other option is grabbing the password with some helper that clears the terminal when typing and then using the on_receive option to send the password when needed.

Semi interactive commands

It's possible to automatically respond to promps by specifying a custom handler in your command. This can be abused to automatically login for example (use at your own risk):

public_task(:login_and_ls, fn ->
  on_receive = fn pid, %{buffer: [last | _]} = state ->
    cond do
      last =~ ~r/Permission denied/ ->
        raise("Password failed")

      last =~ ~r/password: $/ ->
        Minex.Command.send_input(pid, "your_password\n")
        {:cont, state}

      true ->
        {:cont, state}
    end
  end

  set(:host, "[email protected]")
  set(:remote_command_options, [on_receive: on_receive, pty: true])

  run(:remote, fn ->
    command("ls")
  end)
end)

Dry run

Output the commands that would be executed otherwise:

task(:dry_run, fn [fun] ->
  IO.puts "# Dry run:"
  collect(fun)
  |> Enum.join("\n")
  |> IO.puts()
end)

case System.argv() do
  ["dry_run" | args] ->
    run(:dry_run, fn ->
      Minex.run(args)
    end)

  args ->
    Minex.run(args)
end

Local environment variables

Set environment variables for local commands:

Inline:

command("VAR=val; echo $VAR")

Per command:

command("echo $VAR", env: %{"VAR" => "val"})

For all commands:

set(:local_command_options, [interact: true, echo_cmd: true, env: %{"VAR" => "val"}])
command("echo $VAR")

Acknowledgements

Inspired by the Ruby gem Mina and by Bootleg