RssWatcher

A small worker that watches a single RSS feed, parses the changes, and dispatches updates.

Online Docs: https://hexdocs.pm/rss_watcher.

Installation

Dependancies

Add the following to your dependencies:

{:rss_watcher, "~> 0.1.0"}

For easy mode, you can use the default adapters to fetch and parse RSS feeds. Just add the following to your dependancies, and you should be good to go.

{:tesla, "~> 1.2.1"}, # For HTTP requests
{:fiet, "~> 0.2.1"}, # For RSS parsing
{:timex, "~> 3.0"}, # For timestamp parsing

And add Timex to your list of applications.

extra_applications: [ ...,  :timex]

Adapters

RssWatcher.HTTP.Tesla is provided by default. To use, add the following dependancies to your dependency list. See module configuration around middleware, and additional adapter options.

{:tesla, "~> 1.2.1"}

For RSS parsing, RssWatcher.Feed.Fiet is provided by default, and handles parsing XML and timestamps. To use, add the following dependencies to your dependency list.

{:fiet, "~> 0.2.1"},
{:timex, "~> 3.0"}

And add timex to your list of applications.

extra_applications: [ ...  :timex]

Usage

RssWatcher is a worker, so the recommended usage is to add it as a child to your supervisor.

API Example

children = [
  {RssWatcher,
      url: "http://example.com/rss",
      callback: {Notifications, broadcast, ["#channel_id"]},
  }
]

Supervisor.start_link(children, strategy: :one_for_one))

Or, with a dynamic supervisor:

children = [
  {DynamicSupervisor, strategy: :one_for_one, name: MyApp.RssSupervisor}
]

Supervisor.start_link(children, strategy: :one_for_one)

...

DynamicSupervisor.start_child(
  MyApp.RssSupervisor,
  {RssWatcher,
      url: "http://example.com/rss",
      callback: {Notifications, broadcast, ["#channel_id"]}
  }
)

Each RssWatcher worker takes at least a url, and a callback. Additional configuration can be provided to use alternate adapters.

Url

The url should be a string, which resolves to an RSS feed.

Callback

The callback can be in the form of {module, function, arguments}, or an anonymous/suspended function.

If {module, function, arguments} format, the callback will be dispatched with an additional argument - the parsed XML. Otherwise, the parsed XML will be the only argument provided. See below for examples.

Additional Configuration

Additional configuration can be provided to handle dispatching/fetching updates.

• :refresh_interval - integer. How often the feed is checked, in seconds. Defautls to 60.
• :rss_parser - Atom/RSS 2.0 parser module. Defaults to RssWatcher.Feed.Fiet,
• :rss_parser_options- options for the above parser. Defaults to [],
• :http_client - HTTP client for fetching updates. Defaults to RssWatcher.HTTP.Tesla,
• :http_client_options - options for the above client. Default to []. See adapter module for configuration options.

Examples

{RssWatcher,
  url: "http://example.com/rss",
  callback: {Notifications, broadcast, ["#channel_id"]},
}

{RssWatcher,
  [
    url: "http://example.com/rss",
    callback: fn xml -> Notifications.broadcast(xml) end,
  ]
}

{RssWatcher,
  [
    url: "http://example.com/rss",
    callback: &Notifications.broadcast/1,
    refresh_interval: 60
  ]
}