This application is able to respond with a Streaming JSON response of Chuck Norris jokes taken from here
The purpose of this application was to help familiarize myself (and anyone interested) with how Akka Streams can integrate with Akka Actors and Akka HTTP. Also, I was bored and looking for something fun to do 😄.
The Internet Chuck Norris Database returns a discrete JSON response for every HTTP request sent out. Whilst this is okay for most cases, it becomes a bit cumbersome if you want to look at Chuck Norris jokes as you have to keep hitting the endpoint yourself. The goal of this project is to turn those discretized JSON responses into a continuous JSON stream. This is done with the help of Akka HTTP, Akka Actors and Akka Streams.
The JokeFetcher Akka Actor is used to continuously poll the ICNDB
endpoint behind the scenes and publish each discrete JSON response onto
the Event Stream as a JokeEvent.
The JokePublisher Akka Actor is a point of integration between Akka
Actors and Akka Streams. The JokePublisher is created whenever a
request to the /streaming-jokes endpoint which in turn creates an Akka
Stream to stream the response back to the requester. It lives for the
duration of that Stream and gets terminated once the Stream completes
(does not happen in this case because it is an infinite Stream) or when
the Stream is cancelled (happens when the requester does not want
anymore data). As you can see the JokePublisher is tied to the duration
of each Stream. This means if 6 users come in and request data from
/streaming-jokes then 6 actors of JokePublisher will be created, each
of them will be responsible for publishing data into that specific
user's streaming response. The JokePublisher on creation, will
subscribe to the Akka EventStream and listen for JokeEvents and send
them downstream to provide streaming responses. As you can see,
publishing messages to the JokePublisher Actor will end up in the
Akka Stream which is why this is a point of integration between Akka
Actors and Akka Streams when it comes to publishing data into the Akka
Stream. This actor respects backpressure. It will only send information
as fast as the downstream consumer can consume. It will drop messages if
they are coming in too quickly.
Users can hit the /streaming-jokes route in order to get back an SSE
streaming JSON response of Chuck Norris jokes in JSON format.
- Scala 2.11.8
- SBT
sbt runto start the application- Visit
localhost:9000/streaming-jokesto see the Streaming response
Here is an example of how to consume the Stream using JavaScript
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Consuming Streaming JSON</title>
</head>
<body></body>
<script>
var body = document.body;
var eventSource = new EventSource("http://localhost:9000/streaming-jokes");
eventSource.addEventListener('jsonJoke', function(event) {
var joke = JSON.parse(event.data);
body.innerHTML += joke.message + "<br/>";
});
</script>
</html>The above example will print out the SSE Events received from the server in the browser. You may need to use the CORS Chrome Addon
- Akka
- Heiko Seeberger's Akka SSE extension
- Lomig Megard's Akka HTTP CORS extension
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent