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README.md

flow-lite

flow-lite gem - (yet) another (lite) workflow engine; let's you define your workflow steps in Flowfiles; incl. the flow command line tool

Usage

Define the workflow steps in a Flowfile. Example:

step :first_step do
  puts "first_step"
  step :second_step    # note: you can call other steps with step
end

step :second_step do
  puts "second_step"
  step :third_step
end

step :third_step do
  puts "third_step"
end

And then use the flow command line tool to run a step. Example:

$ flow first_step

Note: By default the flow command line tool reads in and looks for ./flowfile, ./Flowfile, ./flowfile.rb, ./Flowfile.rb in that order. Use the -f/--file/--flowfile option to use a different file.

Debugging

Use the -d/--debug option to turn on debugging or pass in DEBUG=t as an environment variable on the command line.

Helper. In your flowfiles you can use the debug? helper to check if debugging is turned on. Example:

step :json do
  outdir = if debug?
             './o'
           else
             realpath( '@openfootball/football.json' )
           end
  #...
end

Prelude / Prolog

Use the -r/--require option to (auto-)require some extra libraries or scripts.

  1. By default the flow command line tool will look for and (auto-)require the ./config.rb script if it exists AND if no extra libraries or scripts are passed along with the -r/--require option.

  2. By default the "prelude / prolog" that always gets auto-required (via the flow-lite gem / library) includes:

require 'pp'
require 'time'
require 'date'
require 'json'
require 'yaml'
require 'fileutils'

require 'uri'
require 'net/http'
require 'net/https'

Tip: See the flow-lite.rb source for the definite always up-to-date list.

(Environment) Variables

On the command line you can pass along (environment) variables using NAME=VALUE to set and NAME= to unset. Example:

$ flow json DEBUG=t           # -or-
$ flow DEBUG=t json

$ flow build DATA=worldcup
$ flow publish VERSION=1.1.0

This will (behind the scene) turn into

ENV[ 'DEBUG' ]   = 't'
ENV[ 'DATA' ]    = 'worldcup'
ENV[ 'VERSION' ] = '1.1.0'

That's it for now.

Backstage Internals / Inside Flowfiles

If you read in a Flowfile the flow machinery builds a new (regular) class derived from Flow::Base and every step becomes a (regular) method. Example:

require 'flow-lite'

flowfile = Flow::Flowfile.load( <<TXT )
  step :hello do
    puts "Hello, world!"
  end

  step :hola do
    puts "¡Hola, mundo!"
  end
TXT

flow = flowfile.flow_class.new   # (auto-)build a flow class (see Note 1)
                                 # and construct/return a new instance
flow.step_hello             #=> "Hello, world!"
flow.step_hola              #=> "¡Hola, mundo!"
flow.step( :hello )         #=> "Hello, world!"
flow.step( :hola )          #=> "¡Hola, mundo!"
flow.class.step_methods     #=> [:hello, :hola]

# or use ruby's (regular) message/metaprogramming machinery
flow.send( :step_hello )    #=> "Hello, world!"
flow.send( :step_hola  )    #=> "¡Hola, mundo!"
# or try
flow.class.instance_methods.grep( /^step_/ ) #=> [:step_hello, :step_hola]
# ...

Note 1: The Flowfile "source / configuration":

step :hello do
  puts "Hello, world!"
end

step :hola do
  puts "¡Hola, mundo!"
end

gets used to (auto-) build (via metaprogramming) a flow class like:

class Greeter < Flow::Base
  def step_hello
    puts "Hello, world!"
  end

  def step_hola
    puts "¡Hola, mundo!"
  end
end

Note: Behind the stage the metaprogramming "class macro" define_step( symbol, method ) or define_step( symbol ) { block } defined in Flow::Base gets used, thus, if you want to create steps in a "hand-coded" class use:

class Greeter < Flow::Base
  define_step :hello do
    puts "Hello, world!"
  end

  define_step :hola do
    puts "¡Hola, mundo!"
  end
end

Tips & Tricks

Auto-include pre-build / pre-defined steps. Use a (regular) Module e.g.:

module GitHubActions
  def step_adduser
     # setup ssh
     ssh_key  = ENV['SSH_KEY']
     ssh_path = File.expand_path( '~/.ssh' )

     FileUtils.mkdir_p( ssh_path )   # make sure path exists
     File.open( "#{ssh_path}/id_rsa", 'w' ) { |f| f.write( ssh_key ) }
     File.chmod( 0600, "#{ssh_path}/id_rsa" )

     # setup git
     user_name  = ENV['GITHUB_NAME']  || 'you'
     user_email = ENV['GITHUB_EMAIL'] || 'you@example.com'

     Git.config( 'user.name',  user_name,  global: true )
     Git.config( 'user.email', user_email, global: true )

     # ...
  end
end

and than use (regular) include e.g.:

class Flow::Base
  include GitHubActions
end

#-or-

Flow::Base.include( GitHubActions )

Now all your flows can (re)use adduser or any other step methods you define.

Real World Examples

Collect GitHub Statistics Fortnightly

Use GitHub Actions to collect GitHub Statistics via GitHub API calls and update the JSON datasets in the /cache.github repo at the yorobot org(anization):

step :clone do
  Mono.clone( '@yorobot/cache.github' )
end


step :update do
  Hubba.config.data_dir = Mono.real_path( '@yorobot/cache.github' )

  username = 'geraldb'
  h = Hubba.reposet( username )
  pp h

  Hubba.update_stats( h )
  Hubba.update_traffic( h )
  puts "Done."
end


step :push do
  msg = "auto-update week #{Date.today.cweek}"

  Mono.open( '@yorobot/cache.github' ) do |proj|
    if proj.changes?
      proj.add( "." )
      proj.commit( msg )
      proj.push
    end
  end
end

(Sources: Flowfile, workflows/update.yml @ yorobot/backup)

Build SQLite database (from Scratch) and Update .JSON Datasets Nightly

Use GitHub Actions to build a SQLite football.db from zero / scratch from the sources in the football.TXT format and than update / generate the football.json datasets.

(Sources: Flowfile, workflows/update.yml @ yorobot/football.json)

Add your example / setup here!

Installation

Use

gem install flow-lite

or add to your Gemfile

gem 'flow-lite'

License

The flow-lite scripts are dedicated to the public domain. Use it as you please with no restrictions whatsoever.