The Runner

Disclaimer

This version is just a rough proof of concept. There is basically no error handling, no argument type checking, no docs, no tests. I just wanted to have my own solution to run commands across multiple servers (ideally in parallel) and that's how this project started. If you somehow come across the library and use it, don't hesitate to open bug / improvement tickets or send me a PR.

Overview

The Runner is a ruby library that provides a solution for running ssh commands across multiple servers. It's supposed to be highly extendable and configurable. It lets you also run commands in parallel.

Installation

gem install the_runner

Usage

Direct

This direct usage example you can try using irb or by embedding it into ruby file.

require 'the_runner'

the_runner = TheRunner.new
the_runner['default'] = TheRunner::Context.new do |context|
    context.add_server('host.example.com')
    context.command = 'echo "Hello World!"'
end
the_runner.run('default')

Therunnerfile

The Runner supports so called Therunnerfile. Below you can find contents of Therunnerfile which is part of the library for demonstration purposes. It contains almost all possible configuration options out there.

TheRunner.context("example-ls") do |context|
  # Adding single server
  context.add_server('host.example.com')
  # Command to run on specified server
  context.command = 'ls -al'
end

TheRunner.context("example-ls-multiple") do |context|
  context.add_server('host.example.com')
  # Adding another server, command will be executed sequentially
  context.add_server('another.example.com')
  context.command = 'ls -al'
end

TheRunner.context("example-ls-multiple-add-servers") do |context|
  # Instead of calling add_server twice, you can call add_servers once with array of servers
  context.add_servers(['host.example.com', 'another.example.com'])
  context.command = 'ls -al'
end

TheRunner.context("example-server-config") do |context|
  # Both add_servers and add_server will yield a server config if you provide a block. In this
  # case both servers will share the same config.
  context.add_servers(['host.example.com', 'another.example.com']) { |config|
    config.runner_options = {
      # Will disable key checks while connecting to server (default: false) by
      # prepending '-o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no'
      :disable_key_checking => true,
      # Will use this username while connecting to server (default: nil, no username
      # would be used)
      :user => 'root',
      # Will enable ssh debugging by adding '-vvv' to the command
      :debug => true,
    }
  }
  context.command = 'ls -al'
end

TheRunner.context("example-mutiple-configs") do |context|
  # We specify one host with specific config
  context.add_server('host.example.com') { |config|
    config.runner_options = {
      :user => 'root',
    }
  }

  # Another host with different config
  context.add_server('another.example.com') { |config|
    config.runner_options = {
      :debug => true,
    }
  }

  # And yet another host without any config (which means: default one)
  context.add_server('yet-another.example.com')
  context.command = 'ls -al'
end

TheRunner.context("example-parallel") do |context|
  context.add_server('host.example.com') { |config|
    config.runner_options = {
      :user => 'root',
    }
  }
  context.add_server('another.example.com') { |config|
    config.runner_options = {
      :debug => true,
    }
  }
  context.add_server('yet-another.example.com')
  context.command = 'ls -al'
  # Parallel option means that the specified command will be executed in parallel
  # (in multiple threads) instead of sequentially.
  context.config.parallel = true
end

# Default context
TheRunner.context do |context|
  context.add_server('host.example.com')
  context.command = 'uptime'
end

And run command in following format:

the_runner <context name>

for example:

the_runner example-ls

inside directory containing the file to execute The Runner in "example-ls" context from the example Therunnerfile.

Things to remember:

• If you specify only one context, it will be by executed always by default, no matter what you specify on command line.
• If you don't specify on command line, "default" will be used if provided.