Petite-lettre is a little gem allowing YAML communication between a process and the child it launches.
The parent process launches its child and passes it a message using this kind of code:
PetiteLettre.call("ruby child_program.rb", { :command => :start_sale, :isbn => "1234567", :price => 12.4 })
The child process read the parent message using this kind of code:
PetiteLettre.receive do |message|
response = {}
if message[:command] == :start_sale
# do something here
raise "Price is too low" if message[:price] < 15.0
response[:status] = "OK"
response[:transaction_id] = "1235"
else
raise "Unknown command '#{message[:command]}'"
end
response
end
Petite-lettre uses $stdin and $stdout by default, although these can be customized with PetiteLettre.receive(input,output).
Nothing stops you from writing a child process in another language (ie: C#, Java), as long as it knows how to read YAML from $stdin and output YAML on $stdout. Just the same – you can write a parent process in another language.
See petite_lettre.rb for implementation details.
Petite-lettre is born out of the need to communicate between a MRI/Shoes front-end and a JRuby/Celerity back-end.
I’m pretty sure there is something already available out there to do that kind of things already. I just could not find them in a reasonable amount of time.
If it’s the case, please mail me so I can bury petite-lettre for ever.
I think I got that idea after using CouchDB for a while. I believe CouchDB uses JSON to communicate between its processes.
- create a C# or Java client
- allow continuous communication (à la server)
- throw petite-lettre to the bin if I discover something that does the same thing at the same level of simplicity
Copyright © 2008 Thibaut Barrère. See LICENSE for details.