kane

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# Kane
Kane. Citizen Kane. Charles Foster Kane, to be exact, Publisher extraordinaire. Rosebud.
Kane is for publishing and subscribing to topics using Google Cloud Pub/Sub.
## Installation
1. Add Kane to your list of dependencies in `mix.exs`:
```elixir
def deps do
  [{:kane, "~> 0.9.0"}]
end
```
2. Configure [Goth](https://github.com/peburrows/goth) (Kane's underlying token storage and retrieval library) with your Google JSON credentials.
## Usage
Pull, process and acknowledge messages via a pre-existing subscription:
```elixir
{:ok, token} = Goth.fetch(MyApp.Goth)
kane = %Kane{
  project_id: my_app_gcp_credentials["project_id"],
  token: token
}
subscription = %Kane.Subscription{
                  name: "my-sub",
                  topic: %Kane.Topic{
                    name: "my-topic"
                  }
                }
{:ok, messages} = Kane.Subscription.pull(kane, subscription)
Enum.each messages, fn(mess)->
  process_message(mess)
end
# acknowledge message receipt in bulk
Kane.Subscription.ack(kane, subscription, messages)
```
Send message via pre-existing subscription:
```elixir
topic   = %Kane.Topic{name: "my-topic"}
message = %Kane.Message{data: %{"hello": "world"}, attributes: %{"random" => "attr"}}
result  = Kane.Message.publish(kane, message, topic)
case result do
  {:ok, _return}    -> IO.puts("It worked!")
  {:error, _reason} -> IO.puts("Should we try again?")
end
```
Hints:
- Attributes have to be Strings (https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessage)
- We base64-encode the message by default (only mandatory when using json - https://cloud.google.com/pubsub/publisher)
For more details, see the [documentation](http://hexdocs.pm/kane).