How to Build a Super Simple HTTP Proxy in Scala in Just 20 Lines of Code

Oct 1, 2023 ยท 3 min read

Scala makes it easy to build networked applications thanks to its concise syntax and strong libraries. Here is an HTTP proxy server in Scala in just 20 lines of code:

First import the libraries we need:

import akka.actor.{Actor, ActorSystem, Props}
import akka.io.{IO, Tcp}
import akka.util.ByteString

Akka provides the actor model for concurrency and socket handling.

Define an actor to handle each client connection:

class ProxyActor extends Actor {

  def receive = {
    case (client: ActorRef, data: ByteString) =>
      // handle request
  }

}

To handle the request we:

  • Extract the URL from the HTTP request
  • val url = extractUrl(data.utf8String)
    
  • Make the proxied GET request
  • val response = Http().singleRequest(Get(url))
    
  • Send the response back to client
  • client ! response.entity.dataBytes
    

    Start the proxy actor when system starts:

    system.actorOf(Props[ProxyActor], "proxy")
    

    This shows the basic structure of an HTTP proxy in Scala using Akka.

    here is the full code:

    import akka.actor.{Actor, ActorSystem, Props}
    import akka.io.{IO, Tcp} 
    import akka.util.ByteString
    
    class ProxyActor extends Actor {
    
      def receive = {
        case (client: ActorRef, data: ByteString) =>
          val url = extractUrl(data.utf8String)
          val response = Http().singleRequest(Get(url))
          client ! response.entity.dataBytes
      }
    
    }
    
    object Main extends App {
    
      val system = ActorSystem("ProxySystem")
      system.actorOf(Props[ProxyActor], "proxy")
    
      IO(Tcp) ! Bind(system.actorOf(Props[PlaintextServer]), "localhost", 8080) 
    
    }

    This implements a simple HTTP proxy actor in Scala using Akka in around 20 lines of code.

    This is great as a learning exercise but it is easy to see that even the proxy server itself is prone to get blocked as it uses a single IP. In this scenario where you may want a proxy that handles thousands of fetches every day using a professional rotating proxy service to rotate IPs is almost a must.

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    The whole thing can be accessed by a simple API like below in any programming language.

    In fact, you don't even have to take the pain of loading Puppeteer as we render Javascript behind the scenes and you can just get the data and parse it any language like Node, Puppeteer or PHP or using any framework like Scrapy or Nutch. In all these cases you can just call the URL with render support like so:

    curl "<http://api.proxiesapi.com/?key=API_KEY&render=true&url=https://example.com>"
    
    

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    <head>
        <title>Example Domain</title>
        <meta charset="utf-8" />
        <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
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