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.

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

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