Pluggable Client Transports / HTTP(S) proxy Support

The client side infrastructure has (unstable) support to plug different transport mechanisms underneath. A client side transport is represented by an instance of akka.http.scaladsl.ClientTransportakka.http.javadsl.ClientTransport:

Scala
@ApiMayChange
trait ClientTransport {
  def connectTo(host: String, port: Int, settings: ClientConnectionSettings)(implicit system: ActorSystem): Flow[ByteString, ByteString, Future[OutgoingConnection]]
}
Java
@ApiMayChange
abstract class ClientTransport {
  def connectTo(host: String, port: Int, settings: ClientConnectionSettings, system: ActorSystem): Flow[ByteString, ByteString, CompletionStage[OutgoingConnection]]
}

A transport implementation defines how the client infrastructure should communicate with a given host.

Note

In our model, SSL/TLS runs on top of the client transport, even if you could theoretically see it as part of the transport layer itself.

Configuring Client Transports

A ClientTransportClientTransport can be configured in the ClientConnectionSettingsClientConnectionSettings. Right now, this is not possible through config files but only by code. First, use ClientConnectionSettings.withTransport to configure a transport, then use ConnectionPoolSettings.withConnectionSettings. ClientConnectionSettingsClientConnectionSettings can be passed to all client-side entry points in HttpHttp.

Predefined Transports

TCP

The default transport is ClientTransport.TCP which simply opens a TCP connection to the target host.

HTTP(S) Proxy

A transport that connects to target servers via an HTTP(S) proxy. An HTTP(S) proxy uses the HTTP CONNECT method (as specified in RFC 7231 Section 4.3.6) to create tunnels to target servers. The proxy itself should transparently forward data to the target servers so that end-to-end encryption should still work (if TLS breaks, then the proxy might be fussing with your data).

This approach is commonly used to securely proxy requests to HTTPS endpoints. In theory it could also be used to proxy requests targeting HTTP endpoints, but we have not yet found a proxy that in fact allows this.

Instantiate the HTTP(S) proxy transport using ClientTransport.httpsProxy(proxyAddress).

Use HTTP(S) proxy with Http().singleRequestHttp.get(...).singleRequest

To make use of an HTTP proxy when using the singleRequest API you simply need to configure the proxy and pass the appropriate settings object when calling the single request method.

Scala
import java.net.InetSocketAddress

import akka.actor.ActorSystem
import akka.stream.ActorMaterializer
import akka.http.scaladsl.{ ClientTransport, Http }

implicit val system = ActorSystem()
implicit val materializer = ActorMaterializer()

val proxyHost = "localhost"
val proxyPort = 8888

val httpsProxyTransport = ClientTransport.httpsProxy(InetSocketAddress.createUnresolved(proxyHost, proxyPort))

val settings = ConnectionPoolSettings(system)
  .withConnectionSettings(ClientConnectionSettings(system)
    .withTransport(httpsProxyTransport))
Http().singleRequest(HttpRequest(uri = "https://google.com"), settings = settings)
Java

final ActorSystem system = ActorSystem.create(); ClientTransport proxy = ClientTransport.httpsProxy(InetSocketAddress.createUnresolved("192.168.2.5", 8080)); ConnectionPoolSettings poolSettingsWithHttpsProxy = ConnectionPoolSettings.create(system) .withConnectionSettings(ClientConnectionSettings.create(system).withTransport(proxy)); final CompletionStage<HttpResponse> responseFuture = Http.get(system) .singleRequest( HttpRequest.create("https://github.com"), Http.get(system).defaultClientHttpsContext(), poolSettingsWithHttpsProxy, // <- pass in the custom settings here system.log());

Use HTTP(S) proxy that requires authentication

In order to use a HTTP(S) proxy that requires authentication, you need to provide HttpCredentialsHttpCredentials that will be used when making the CONNECT request to the proxy:

Scala
import akka.http.scaladsl.model.headers

val proxyAddress = InetSocketAddress.createUnresolved(proxyHost, proxyPort)
val auth = headers.BasicHttpCredentials("proxy-user", "secret-proxy-pass-dont-tell-anyone")

val httpsProxyTransport = ClientTransport.httpsProxy(proxyAddress, auth)

val settings = ConnectionPoolSettings(system)
  .withConnectionSettings(ClientConnectionSettings(system)
    .withTransport(httpsProxyTransport))
Http().singleRequest(HttpRequest(uri = "http://akka.io"), settings = settings)
Java
InetSocketAddress proxyAddress =
  InetSocketAddress.createUnresolved("192.168.2.5", 8080);
HttpCredentials credentials =
  HttpCredentials.createBasicHttpCredentials("proxy-user", "secret-proxy-pass-dont-tell-anyone");

ClientTransport proxy = ClientTransport.httpsProxy(proxyAddress, credentials); // include credentials
ConnectionPoolSettings poolSettingsWithHttpsProxy = ConnectionPoolSettings.create(system)
    .withConnectionSettings(ClientConnectionSettings.create(system).withTransport(proxy));

final CompletionStage<HttpResponse> responseFuture =
    Http.get(system)
        .singleRequest(
              HttpRequest.create("https://github.com"),
              Http.get(system).defaultClientHttpsContext(),
              poolSettingsWithHttpsProxy, // <- pass in the custom settings here
              system.log());

Use HTTP(S) proxy with Http().singleWebSocketRequestHttp.get(…).singleWebSocketRequest

Making use of an HTTP proxy when using the singleWebSocketRequest is done like using singleRequest, except you set ClientConnectionSettings instead of ConnectionPoolSettings:

Scala
import java.net.InetSocketAddress

import akka.actor.ActorSystem
import akka.NotUsed
import akka.stream.ActorMaterializer
import akka.http.scaladsl.{ ClientTransport, Http }
import akka.http.scaladsl.settings.ClientConnectionSettings
import akka.http.scaladsl.model.ws._
import akka.stream.scaladsl._

implicit val system = ActorSystem()
implicit val materializer = ActorMaterializer()

val flow: Flow[Message, Message, NotUsed] =
  Flow.fromSinkAndSource(
    Sink.foreach(println),
    Source.single(TextMessage("hello world!")))

val proxyHost = "localhost"
val proxyPort = 8888

val httpsProxyTransport = ClientTransport.httpsProxy(InetSocketAddress.createUnresolved(proxyHost, proxyPort))

val settings = ClientConnectionSettings(system).withTransport(httpsProxyTransport)
Http().singleWebSocketRequest(WebSocketRequest(uri = "wss://example.com:8080/some/path"), clientFlow = flow, settings = settings)
Java

final ActorSystem system = ActorSystem.create(); final Materializer materializer = ActorMaterializer.create(system); final Flow<Message, Message, NotUsed> flow = Flow.fromSinkAndSource( Sink.foreach(System.out::println), Source.single(TextMessage.create("hello world"))); ClientTransport proxy = ClientTransport.httpsProxy(InetSocketAddress.createUnresolved("192.168.2.5", 8080)); ClientConnectionSettings clientSettingsWithHttpsProxy = ClientConnectionSettings.create(system) .withTransport(proxy); Http.get(system) .singleWebSocketRequest( WebSocketRequest.create("wss://example.com:8080/some/path"), flow, Http.get(system).defaultClientHttpsContext(), null, clientSettingsWithHttpsProxy, // <- pass in the custom settings here system.log(), materializer);

Use HTTP(S) proxy that requires authentication for Web Sockets

Here is an example for Web Socket:

Scala
import akka.http.scaladsl.model.headers

val proxyAddress = InetSocketAddress.createUnresolved(proxyHost, proxyPort)
val auth = headers.BasicHttpCredentials("proxy-user", "secret-proxy-pass-dont-tell-anyone")

val httpsProxyTransport = ClientTransport.httpsProxy(proxyAddress, auth)

val settings = ClientConnectionSettings(system).withTransport(httpsProxyTransport)
Http().singleWebSocketRequest(WebSocketRequest(uri = "wss://example.com:8080/some/path"), clientFlow = flow, settings = settings)
Java
InetSocketAddress proxyAddress =
  InetSocketAddress.createUnresolved("192.168.2.5", 8080);
HttpCredentials credentials =
  HttpCredentials.createBasicHttpCredentials("proxy-user", "secret-proxy-pass-dont-tell-anyone");

ClientTransport proxy = ClientTransport.httpsProxy(proxyAddress, credentials); // include credentials
ClientConnectionSettings clientSettingsWithHttpsProxy = ClientConnectionSettings.create(system)
  .withTransport(proxy);

Http.get(system)
  .singleWebSocketRequest(
    WebSocketRequest.create("wss://example.com:8080/some/path"),
    flow,
    Http.get(system).defaultClientHttpsContext(),
    null,
    clientSettingsWithHttpsProxy, // <- pass in the custom settings here
    system.log(),
    materializer);

Implementing Custom Transports

Implement ClientTransport.connectTo to implement a custom client transport.

Here are some ideas for custom (or future predefined) transports:

  • SSH tunnel transport: connects to the target host through an SSH tunnel
  • Per-host configurable transport: allows choosing transports per target host
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