# Herald
Herald is a library to exchange async messages between systems through a message broker.
These library support AMQP based message brokers
## Installation
Add in your `mix.exs` and run `mix deps.get`:
```elixir
def deps do
[
{:herald, "~> 0.1.0"}
]
end
```
# Getting start
## Subscriptions
1. Create you message schema:
```elixir
defmodule MyApp.Message do
use Herald.Message
payload do
field :age, :integer
field :name, :string, required: true
end
end
```
2. Create your processor function
Processor function will work as a callback function when a message is received.
```elixir
defmodule MyApp.Message do
use Herald.Message
payload do
field :age, :integer
field :name, :string, required: true
end
def my_processor(%MyApp.Message{} = message) do
if do_some_stuff_with(message) do
{:ok, message}
else
{:error, :my_bad_error}
end
end
end
```
3. Create your Router
Router will say for library what `schema` and `processor` use for each queue.
In example bellow, any message received in queue `my_queue` will be validated by schema `MyApp.Message`, and processed by function `&MyApp.Message.my_processor/1`.
```elixir
defmodule MyApp.Router do
use Herald.Router
route "my_queue",
schema: MyApp.Message,
processor: &MyApp.Message.my_processor/1
end
```
4. Configure this
Finaly, need inform Herald what is the module where router is configured:
```elixir
config :herald,
router: Develop.Router
```
## Publishing
Publications can be performed as bellow:
```elixir
alias Herald.AMQP.Publisher
MyApp.Message.new("queue", %{
"age" => 70,
"name" => "Dennis Ritchie"
})
|> Publisher.perform()
```
# Documentation
Docs for this library can
be found at [https://hexdocs.pm/herald](https://hexdocs.pm/herald).
