Redis adapter for Yggdrasil

This project is a Redis adapter for Yggdrasil publisher/subscriber.

Small example

The following example uses Redis adapter to distribute messages:

iex(1)> channel = %Yggdrasil.Channel{name: "some_channel", adapter: :redis}
iex(2)> Yggdrasil.subscribe(channel)
iex(3)> flush()
{:Y_CONNECTED, %Yggdrasil.Channel{(...)}}

and to publish a message for the subscribers:

iex(4)> Yggdrasil.publish(channel, "message")
iex(5)> flush()
{:Y_EVENT, %Yggdrasil.Channel{(...)}, "message"}

When the subscriber wants to stop receiving messages, then it can unsubscribe from the channel:

iex(6)> Yggdrasil.unsubscribe(channel)
iex(7)> flush()
{:Y_DISCONNECTED, %Yggdrasil.Channel{(...)}}

Redis adapter

The Redis adapter has the following rules:

• The adapter name is identified by the atom :redis.
• The channel name must be a string.
• The transformer must encode to a string. From the transformers provided it defaults to :default, but :json can also be used.
• Any backend can be used (by default is :default).

The following is an example of a valid channel for both publishers and subscribers:

%Yggdrasil.Channel{
  name: "redis_channel_name",
  adapter: :redis,
  transformer: :json
}

It will expect valid JSONs from Redis and it will write valid JSONs in Redis.

Redis configuration

Uses the list of options for Redix, but the more relevant optuons are shown below:

• hostname - Redis hostname (defaults to "localhost").
• port - Redis port (defaults to 6379).
• password - Redis password (defaults to "").

The following shows a configuration with and without namespace:

# Without namespace
config :yggdrasil,
  redis: [hostname: "redis.zero"]

# With namespace
config :yggdrasil, RedisOne,
  redis: [
    hostname: "redis.one",
    port: 1234
  ]

Also the options can be provided as OS environment variables. The available variables are:

• YGGDRASIL_REDIS_HOSTNAME or <NAMESPACE>_YGGDRASIL_REDIS_HOSTNAME.
• YGGDRASIL_REDIS_PORT or <NAMESPACE>_YGGDRASIL_REDIS_PORT.
• YGGDRASIL_REDIS_PASSWORD or <NAMESPACE>_YGGDRASIL_REDIS_PASSWORD.
• YGGDRASIL_REDIS_DATABASE or <NAMESPACE>_YGGDRASIL_REDIS_DATABASE.

where <NAMESPACE> is the snakecase of the namespace chosen e.g. for the namespace RedisTwo, you would use REDIS_TWO as namespace in the OS environment variable.

Installation

Using this Redis adapter with Yggdrasil is a matter of adding the available hex package to your mix.exs file e.g:

def deps do
  [{:yggdrasil_redis, "~> 4.1"}]
end

Running the tests

A docker-compose.yml file is provided with the project. If you don't have a Redis database, but you do have Docker installed, then just do:

$ docker-compose up --build

And in another shell run:

$ mix deps.get
$ mix test

Relevant projects used

• Redix.PubSub: Redis pubsub.

Author

Alexander de Sousa.

License

Yggdrasil is released under the MIT License. See the LICENSE file for further details.