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A simple library for Elixir that provides json over STDIO
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Starts a pool of workers that communicate with an external script via JSON over STDIN/STDOUT.

Originally written to use react-stdio but can be used with any process that reads a JSON object from STDIN and outputs JSON on STDOUT.


If available in Hex, the package can be installed as:

  1. Add std_json_io to your list of dependencies in mix.exs:

    def deps do [{:std_json_io, "~> 0.1.0"}] end

  2. Ensure std_json_io is started before your application:

    def application do [applications: [:std_json_io]] end


Define a module and use StdJsonIo.

defmodule MyApp.ReactIo do
  use StdJsonIo, otp_app: :my_app

When you use StdJsonIo your module becomes a supervisor. You'll need to add it to your supervision tree.

children = [
  # snip
  supervisor(MyApp.ReactIo, [])

opts = [strategy: :one_for_one, name: MyApp]

Supervisor.start_link(children, opts)


You can either configure as additional arguments of the use statement, or in your config file.

config :my_app, MyApp.ReactIo,
  pool_size: 20, # default 5
  max_overflow: 10, # default 10
  script: "path/to/script", # for react-io use "react-stdio"
  watch_files: [
    Path.join([__DIR__, "../priv/server/js/component.js"]) # do not watch files in dev
  • script - the script to run for the IO server
  • watch_files - A list of files to watch for changes. When the file changes, kill the IO worker and restart, picking up any changes. Use only in dev.
  • pool_size - The size for the pool of workers - See poolboy size
  • max_overflow - The poolboy max_overflow
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