How do I terminate an akka websocket connection from the server side? - akka-stream

Question

I seem unable to terminate a websocket connection from the server side of the connection using the recommended approach of calling terminate() on the ServerBinding.
I have included code below that establishes a connection, terminates it from the server side, waits for termination, then sends messages from the client. All messages are successfully handled by the server after termination.
How do I terminate a web-socket connection from the server side?
public class AkkaWebSocketServerTerminateTest {
private static final Logger LOGGER = LoggerFactory.getLogger(AkkaWebSocketServerTerminateTest.class);
#Test
public void clientConnectsServer_ServerGracefullyTerminatesConnection() throws ExecutionException, InterruptedException, TimeoutException {
ActorSystem system = ActorSystem.create();
Materializer materializer = ActorMaterializer.create(system);
Http http = Http.get(system);
/* SERVER */
Flow<Message, Message, CompletionStage<Done>> serverSideHandlerFlow = Flow
.of(Message.class)
.via(WebsocketLayer.messageToStringFlow())
.map(s -> {
LOGGER.debug("handling {}", s);
return "handled " + s;
})
.map(s -> (Message) TextMessage.create(s))
.alsoToMat(Sink.ignore(), Keep.right());
CompletionStage<ServerBinding> serverBindingCompletionStage = http.bindAndHandleSync(
httpRequest -> WebSocket.handleWebSocketRequestWith(httpRequest, serverSideHandlerFlow),
ConnectHttp.toHost("localhost", 9999),
materializer);
ServerBinding serverBinding = serverBindingCompletionStage.toCompletableFuture().get(3, TimeUnit.SECONDS);// wait for binding
/* CLIENT */
Sink<Message, CompletionStage<Done>> sink
= Flow.of(Message.class)
.via(WebsocketLayer.messageToStringFlow())
.toMat(Sink.foreach(s -> LOGGER.debug("client received message: '{}'", s)), Keep.right());
CompletableFuture<SourceQueueWithComplete<String>> futureClientSideSourceQueue = new CompletableFuture<>();
Source<Message, SourceQueueWithComplete<String>> source
= Source.<String>queue(0, OverflowStrategy.backpressure())
.alsoToMat(Sink.foreach(s -> LOGGER.debug("client sending '{}'", s)), Keep.left())
.map(s -> (Message) TextMessage.create(s))
.mapMaterializedValue(sourceQueue -> {
futureClientSideSourceQueue.complete(sourceQueue);
return sourceQueue;
});
Flow<Message, Message, CompletionStage<Done>> clientFlow = Flow.fromSinkAndSourceCoupledMat(sink, source, Keep.left());
WebSocketRequest webSocketRequest
= WebSocketRequest.create("ws://localhost:9999");
Pair<CompletionStage<WebSocketUpgradeResponse>, CompletionStage<Done>> clientPair
= http.singleWebSocketRequest(webSocketRequest,
clientFlow,
materializer);
CompletionStage<WebSocketUpgradeResponse> clientSideUpgradeResponse = clientPair.first();
CompletionStage<Done> clientSideConnected = clientSideUpgradeResponse.thenApply(upgrade -> {
if (upgrade.response().status().equals(StatusCodes.SWITCHING_PROTOCOLS)) {
return Done.getInstance();
} else {
throw new RuntimeException("Connection failed: " + upgrade.response().status());
}
});
CompletionStage<Done> clientSideClosed = clientPair.second();
clientSideConnected.thenAccept(done -> {
LOGGER.debug("Client connected");
LOGGER.debug("Terminating all connections with a 1 second hard deadline");
CompletionStage<HttpTerminated> onceAllConnectionsTerminated
= serverBinding.terminate(Duration.ofSeconds(1));
serverBinding.whenTerminated().thenAccept(terminated -> {
LOGGER.debug("whenTerminated() -> terminated");
});
onceAllConnectionsTerminated.toCompletableFuture()
.thenAccept(terminated -> {
LOGGER.debug("All connections terminated.");
try {
LOGGER.debug("Waiting 5 seconds before sending messages from the client to the terminated server.");
Thread.sleep(5000); // wait 5 seconds
SourceQueueWithComplete<String> queue = futureClientSideSourceQueue.get();
queue.offer("message 1");
queue.offer("message 2");
queue.offer("message 3");
queue.offer("message 4");
} catch (InterruptedException e) {
e.printStackTrace();
} catch (ExecutionException e) {
e.printStackTrace();
}
});
});
try {
LOGGER.debug("Waiting 15 seconds for client connection to close.");
clientSideClosed
.thenAccept(done -> LOGGER.debug("Client connection closed"))
.toCompletableFuture()
.get(15, TimeUnit.SECONDS); // wait for connection to close
} catch (InterruptedException e) {
LOGGER.error("Interrupted waiting for client connection to close", e);
} catch (TimeoutException e) {
LOGGER.error("Timeout waiting for client connection to close", e);
}
}
}
I get the following output:
[DEBUG] [10/25/2018 12:14:18.763] [main] [EventStream(akka://default)] logger log1-Logging$DefaultLogger started
[DEBUG] [10/25/2018 12:14:18.780] [main] [EventStream(akka://default)] Default Loggers started
[DEBUG] [10/25/2018 12:14:19.297] [main] [AkkaSSLConfig(akka://default)] Initializing AkkaSSLConfig extension...
[DEBUG] [10/25/2018 12:14:19.306] [main] [AkkaSSLConfig(akka://default)] buildHostnameVerifier: created hostname verifier: com.typesafe.sslconfig.ssl.DefaultHostnameVerifier#31c7528f
[DEBUG] [10/25/2018 12:14:20.343] [default-akka.actor.default-dispatcher-6]
[akka://default/system/IO-TCP/selectors/$a/0] Successfully bound to /127.0.0.1:9999
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:130 - Waiting 15 seconds for client connection to close.
[DEBUG] [10/25/2018 12:14:20.479] [default-akka.actor.default-dispatcher-4]
[akka://default/system/IO-TCP/selectors/$a/1] Resolving localhost before connecting
[DEBUG] [10/25/2018 12:14:20.496] [default-akka.actor.default-dispatcher-6]
[akka://default/system/IO-DNS] Resolution request for localhost from Actor[akka://default/system/IO-TCP/selectors/$a/1#1366663132]
[DEBUG] [10/25/2018 12:14:20.536] [default-akka.actor.default-dispatcher-6]
[akka://default/system/IO-TCP/selectors/$a/1] Attempting connection to [localhost/127.0.0.1:9999]
[DEBUG] [10/25/2018 12:14:20.537] [default-akka.actor.default-dispatcher-4]
[akka://default/system/IO-TCP/selectors/$a/0] New connection accepted
[DEBUG] [10/25/2018 12:14:20.538] [default-akka.actor.default-dispatcher-6]
[akka://default/system/IO-TCP/selectors/$a/1] Connection established to [localhost:9999]
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:104 - Client connected
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:105 - Terminating all connections with a 1 second hard deadline
[DEBUG] [10/25/2018 12:14:20.642] [default-akka.actor.default-dispatcher-13]
[akka://default/system/IO-TCP/selectors/$a/0] Unbinding endpoint /127.0.0.1:9999
[DEBUG] [10/25/2018 12:14:20.643] [default-akka.actor.default-dispatcher-13]
[akka://default/system/IO-TCP/selectors/$a/0] Unbound endpoint /127.0.0.1:9999, stopping listener
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:108 - whenTerminated() -> terminated
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:112 - All connections terminated.
2018-10-25 12:14:20 DEBUG AkkaWebSocketServerTerminateTest:114 - Waiting 5 seconds before sending messages from the client to the terminated server.
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:76 - client sending 'message 1'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:76 - client sending 'message 2'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:76 - client sending 'message 3'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:76 - client sending 'message 4'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:53 - handling message 1
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:53 - handling message 2
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:70 - client received message: 'handled message 1'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:53 - handling message 3
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:53 - handling message 4
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:70 - client received message: 'handled message 2'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:70 - client received message: 'handled message 3'
2018-10-25 12:14:25 DEBUG AkkaWebSocketServerTerminateTest:70 - client received message: 'handled message 4'
2018-10-25 12:14:35 ERROR AkkaWebSocketServerTerminateTest:138 - Timeout waiting for client connection to close

Answer 1

I think explicit termination is not possible but you can set akka.http.server.idle-timeout according to note from their documentation
Inactive WebSocket connections will be dropped according to the idle-timeout settings. In case you need to keep inactive connections alive, you can either tweak your idle-timeout or inject ‘keep-alive’ messages regularly.