Calling Elixir from Ruby

What is the best (or maybe simplest) way to call Elixir functions from Ruby?

I have a Rails application in which we are gradually porting functions in it over to an Elixir application. I could, of course, add Phoenix to the Elixir app and make http/json calls to it, but it seems like there ought to be a more efficient method.

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This is one approach:

You could also have the Ruby application launch the Elixir application, or vice-versa, and communicate one to the other over stdin and stdout (using something like the External Term Format for which there are Ruby Gems available).

Really any IPC mechanism on the platform you are using should be able to let the Ruby and Elixir processes communicate, it doesn’t have to be done over HTTP.

On the Elixir/Erlang side, you should look into “Ports”. At the end of the day your goal is not to call functions in Elixir so much as it is to send a message to an Elixir process and have it execute some functions.

This isn’t really an Elixir/Ruby problem so much as a systems integration issue—anything you’d do to integrate two services normally should also apply.

HTTP calls are probably the least problematic as you can treat them synchronously. However if you can handle asynchronicity in the Rails application, then my favorite means of doing this kind of thing is a durable message queue. You’ve got a plethora of choices there ranging from sidekiq-style queues in Redis (and there are at least a couple of options for consuming sidekiq format messages in Elixir) to AMQP servers like RabbitMQ to something hosted like AWS SQS. Treat the functions as command messages and send back a response message from Elixir to be further dealt with by the Rails app.

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