RedisMessageCapsule

Send messages between node or rails apps asynchronously (via redis).

• report an issue with the ruby version
• report an issue with the node version

Installation

in node:

$ npm install redis_message_capsule

in ruby:

$ gem install redis_message_capsule

Usage

The purpose of RedisMessageCapsule is to enable separate apps to communicate with each other asynchronously.

The ruby implementation listens for messages in a separate thread, and node listens in a separate Fiber.

Make sure redis is running:

The code below defaults to using redis running on localhost

Open 2 terminal windows to simulate any mixture of ruby or node apps:

Both windows can be ruby, can be node, or one can be ruby and one can be node.

To Send Messages From Window 1

in node:

$ node
require('redis_message_capsule')
redisurl = 'redis://127.0.0.1:6379/' 
capsule = RedisMessageCapsule.capsule(redisurl)
cat = capsule.channel('cat')
cat.send('meow')
cat.send('meow')

in ruby:

$ irb
require('redis_message_capsule')
redisurl = 'redis://127.0.0.1:6379/' 
capsule = RedisMessageCapsule.capsule(redisurl)
cat = capsule.channel('cat')
cat.send('meow')
cat.send('meow')

To Receive messages In Window 2

in node:

$ node
require('redis_message_capsule')
redisurl = 'redis://127.0.0.1:6379/' 
capsule = RedisMessageCapsule.capsule(redisurl)
cat = capsule.channel('cat')
cat.register(function(err, message){ console.log(message) })

in ruby:

$ irb
require('redis_message_capsule')
redisurl = 'redis://127.0.0.1:6379/' 
capsule = RedisMessageCapsule.capsule(redisurl)
cat = capsule.channel('cat')
cat.register { |msg|  puts msg }

To Send More Messages From Window 1

in node:

cat.send(9)
talk = { say: 'roar', time: new Date() }        // <- to create a hash in node
cat.send( talk )

in ruby:

cat.send(9)
talk = { say: 'grrrrrr', time: Time.now }       #  <- to create a hash in ruby
cat.send( talk )

• Use the module to create as many capsules as you want (only need one capsule for each redisurl:redisdbnum)
• Use a capsule to create as many channels as you want (use 'ns:channelname' to add a namespace to your channel)
• Use a channel to send as many messages as you want (be sure the data you send can be serialized to json )
• Use a channel to register as many handlers as you want (all registered handlers on a channel will get messages)
• Send messages between any mixture of apps: [ node <-> node ] or [ ruby <-> ruby ] or [ node <-> ruby ]

Advanced Usage

This module sends messages in a queue rather than a typical pub/sub model: messages are not broadcast to all apps.

Multiple Listeners on a Channel Will Round Robin

• If multiple apps are listening on the same channel, only one will actually receive the message and pass it on to its registered handlers for processing.
• Listeners run in their own thread (in ruby) or fiber (in node) and may block waiting for a message.
• When a message comes in, only the app that was waiting the longest will receive it.

Environment

In order for 2 apps to send messages to each other, they must bind a capsule to the same redis DB and select the same db number.

By default, RedisMessageCapsule will:

• select 9 for test environment
• select 8 for development environment
• select 7 for production environment The selected db can also be overriden when materializing a capsule (examples are below).

If 2 apps are not sending messages to each other:

• check that they are both in the same environment (test, development, production)
• or be sure to override using same redisdb when materializing a capsule.

Environment for node

In node use one of the following to set your environment

process.env.NODE_ENV = 'test'          // redisDB.select 9
process.env.NODE_ENV = 'development'   // redisDB.select 8 * Default
process.env.NODE_ENV = 'production'    // redisDB.select 7

Alternatively, you can specify exactly what you want when materializing a capsule:

RedisMessageCapsule = require('redis_message_capsule')
redisurl = process.env.REDIS_URL || process.env.REDISTOGO_URL || 'redis://127.0.0.1:6379/' 
redisdb = 5
capsule = RedisMessageCapsule.capsule(redisurl, redisdb)

Environment for ruby

In ruby use one of the following to set your environment

ENV["RACK_ENV"] = 'test'          // redisDB.select 9
ENV["RACK_ENV"] = 'development'   // redisDB.select 8  * Default
ENV["RACK_ENV"] = 'production'    // redisDB.select 7

Alternatively, you can specify exactly what you want when materializing a capsule:

require 'redis_message_capsule'
redisurl = ENV["REDIS_URL"] || ENV["REDISTOGO_URL"] || "redis://127.0.0.1:6379/"
redisdb = 5
capsule = RedisMessageCapsule.capsule redisurl, redisdb

To build the gem locally:

git clone git@github.com:arbind/redis_message_capsule-gem.git
cd redis_message_capsule-gem
bundle

gem uninstall redis_message_capsule
gem build redis_message_capsule.gemspec
rake install

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request