Support keepAlive in WebSocket client

See gh-608

spring-graphql-docs/modules/ROOT/pages/client.adoc

@@ -165,6 +165,13 @@ existing `WebSocketGraphQlClient` to create a new instance with customized setti
 
 ----
 
+If you'd like the client to send regular graphql ping messages to the server, you can add these by adding `keepalive(long seconds)` to the builder
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+    WebSocketGraphQlClient graphQlClient = WebSocketGraphQlClient.builder(url, client)
+        .keepalive(30)
+        .build();
+----
 
 [[client.websocketgraphqlclient.interceptor]]
 ==== Interceptor

spring-graphql/src/main/java/org/springframework/graphql/client/DefaultWebSocketGraphQlClientBuilder.java

@@ -49,6 +49,7 @@ final class DefaultWebSocketGraphQlClientBuilder
 
 	private final CodecConfigurer codecConfigurer;
 
+	private long keepalive;
 
 	/**
 	 * Constructor to start via {@link WebSocketGraphQlClient#builder(String, WebSocketClient)}.
@@ -57,13 +58,28 @@ final class DefaultWebSocketGraphQlClientBuilder
 		this(toURI(url), client);
 	}
 
+	/**
+	 * Constructor to start via {@link WebSocketGraphQlClient#builder(String, WebSocketClient, long)}.
+	 */
+	DefaultWebSocketGraphQlClientBuilder(String url, WebSocketClient client, long keepalive) {
+		this(toURI(url), client, keepalive);
+	}
+
 	/**
 	 * Constructor to start via {@link WebSocketGraphQlClient#builder(URI, WebSocketClient)}.
 	 */
 	DefaultWebSocketGraphQlClientBuilder(URI url, WebSocketClient client) {
+		this(url, client, 0);
+	}
+
+	/**
+	 * Constructor to start via {@link WebSocketGraphQlClient#builder(URI, WebSocketClient, long)}.
+	 */
+	DefaultWebSocketGraphQlClientBuilder(URI url, WebSocketClient client, long keepalive) {
 		this.url = url;
 		this.webSocketClient = client;
 		this.codecConfigurer = ClientCodecConfigurer.create();
+		this.keepalive = keepalive;
 	}
 
 	/**
@@ -75,6 +91,7 @@ final class DefaultWebSocketGraphQlClientBuilder
 		this.headers.putAll(transport.getHeaders());
 		this.webSocketClient = transport.getWebSocketClient();
 		this.codecConfigurer = transport.getCodecConfigurer();
+		this.keepalive = transport.getKeepAlive();
 	}
 
 
@@ -119,12 +136,18 @@ public WebSocketGraphQlClient build() {
 				CodecDelegate.findJsonDecoder(this.codecConfigurer));
 
 		WebSocketGraphQlTransport transport = new WebSocketGraphQlTransport(
-				this.url, this.headers, this.webSocketClient, this.codecConfigurer, getInterceptor());
+				this.url, this.headers, this.webSocketClient, this.codecConfigurer, getInterceptor(), this.keepalive);
 
 		GraphQlClient graphQlClient = super.buildGraphQlClient(transport);
 		return new DefaultWebSocketGraphQlClient(graphQlClient, transport, getBuilderInitializer());
 	}
 
+	@Override
+	public WebSocketGraphQlClient.Builder<DefaultWebSocketGraphQlClientBuilder> keepalive(long keepalive) {
+		this.keepalive = keepalive;
+		return this;
+	}
+
 	private WebSocketGraphQlClientInterceptor getInterceptor() {
 
 		List<WebSocketGraphQlClientInterceptor> interceptors = getInterceptors().stream()

spring-graphql/src/main/java/org/springframework/graphql/client/WebSocketGraphQlClient.java

@@ -64,6 +64,16 @@ static WebSocketGraphQlClient create(URI url, WebSocketClient webSocketClient) {
 		return builder(url, webSocketClient).build();
 	}
 
+	/**
+	 * Create a {@link WebSocketGraphQlClient}.
+	 * @param url the GraphQL endpoint URL
+	 * @param webSocketClient the underlying transport client to use
+	 * @param keepalive the delay in seconds between sending ping messages, or 0 to disable
+	 */
+	static WebSocketGraphQlClient create(URI url, WebSocketClient webSocketClient, long keepalive) {
+		return builder(url, webSocketClient).keepalive(keepalive).build();
+	}
+
 	/**
 	 * Return a builder for a {@link WebSocketGraphQlClient}.
 	 * @param url the GraphQL endpoint URL
@@ -73,6 +83,16 @@ static Builder<?> builder(String url, WebSocketClient webSocketClient) {
 		return new DefaultWebSocketGraphQlClientBuilder(url, webSocketClient);
 	}
 
+	/**
+	 * Return a builder for a {@link WebSocketGraphQlClient}.
+	 * @param url the GraphQL endpoint URL
+	 * @param webSocketClient the underlying transport client to use
+	 * @param keepalive the delay in seconds between sending ping messages, or 0 to disable
+	 */
+	static Builder<?> builder(String url, WebSocketClient webSocketClient, long keepalive) {
+		return new DefaultWebSocketGraphQlClientBuilder(url, webSocketClient, keepalive);
+	}
+
 	/**
 	 * Return a builder for a {@link WebSocketGraphQlClient}.
 	 * @param url the GraphQL endpoint URL
@@ -82,6 +102,16 @@ static Builder<?> builder(URI url, WebSocketClient webSocketClient) {
 		return new DefaultWebSocketGraphQlClientBuilder(url, webSocketClient);
 	}
 
+	/**
+	 * Return a builder for a {@link WebSocketGraphQlClient}.
+	 * @param url the GraphQL endpoint URL
+	 * @param webSocketClient the underlying transport client to use
+	 * @param keepalive the delay in seconds between sending ping messages, or 0 to disable
+	 */
+	static Builder<?> builder(URI url, WebSocketClient webSocketClient, long keepalive) {
+		return new DefaultWebSocketGraphQlClientBuilder(url, webSocketClient, keepalive);
+	}
+
 
 	/**
 	 * Builder for a GraphQL over WebSocket client.
@@ -95,6 +125,8 @@ interface Builder<B extends Builder<B>> extends WebGraphQlClient.Builder<B> {
 		@Override
 		WebSocketGraphQlClient build();
 
+		Builder<B> keepalive(long keepalive);
+
 	}
 
 }

spring-graphql/src/main/java/org/springframework/graphql/client/WebSocketGraphQlTransport.java

@@ -17,6 +17,7 @@
 package org.springframework.graphql.client;
 
 import java.net.URI;
+import java.time.Duration;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -67,10 +68,12 @@ final class WebSocketGraphQlTransport implements GraphQlTransport {
 
 	private final Mono<GraphQlSession> graphQlSessionMono;
 
+	private final long keepalive;
+
 
 	WebSocketGraphQlTransport(
 			URI url, @Nullable HttpHeaders headers, WebSocketClient client, CodecConfigurer codecConfigurer,
-			WebSocketGraphQlClientInterceptor interceptor) {
+			WebSocketGraphQlClientInterceptor interceptor, long keepalive) {
 
 		Assert.notNull(url, "URI is required");
 		Assert.notNull(client, "WebSocketClient is required");
@@ -80,8 +83,9 @@ final class WebSocketGraphQlTransport implements GraphQlTransport {
 		this.url = url;
 		this.headers.putAll((headers != null) ? headers : HttpHeaders.EMPTY);
 		this.webSocketClient = client;
+		this.keepalive = keepalive;
 
-		this.graphQlSessionHandler = new GraphQlSessionHandler(codecConfigurer, interceptor);
+		this.graphQlSessionHandler = new GraphQlSessionHandler(codecConfigurer, interceptor, keepalive);
 
 		this.graphQlSessionMono = initGraphQlSession(this.url, this.headers, client, this.graphQlSessionHandler)
 				.cacheInvalidateWhen(GraphQlSession::notifyWhenClosed);
@@ -162,6 +166,10 @@ public Flux<GraphQlResponse> executeSubscription(GraphQlRequest request) {
 		return this.graphQlSessionMono.flatMapMany((session) -> session.executeSubscription(request));
 	}
 
+	public long getKeepAlive() {
+		return keepalive;
+	}
+
 
 	/**
 	 * Client {@code WebSocketHandler} for GraphQL that deals with WebSocket
@@ -183,11 +191,15 @@ private static class GraphQlSessionHandler implements WebSocketHandler {
 
 		private final AtomicBoolean stopped = new AtomicBoolean();
 
+		private final long keepalive;
 
-		GraphQlSessionHandler(CodecConfigurer codecConfigurer, WebSocketGraphQlClientInterceptor interceptor) {
+
+		GraphQlSessionHandler(CodecConfigurer codecConfigurer, WebSocketGraphQlClientInterceptor interceptor,
+							  long keepalive) {
 			this.codecDelegate = new CodecDelegate(codecConfigurer);
 			this.interceptor = interceptor;
 			this.graphQlSessionSink = Sinks.unsafe().one();
+			this.keepalive = keepalive;
 		}
 
 
@@ -245,7 +257,7 @@ public Mono<Void> handle(WebSocketSession session) {
 					session.send(connectionInitMono.concatWith(graphQlSession.getRequestFlux())
 							.map((message) -> this.codecDelegate.encode(session, message)));
 
-			Mono<Void> receiveCompletion = session.receive()
+			Flux<Void> receiveCompletion = session.receive()
 					.flatMap((webSocketMessage) -> {
 						if (sessionNotInitialized()) {
 							try {
@@ -276,6 +288,7 @@ public Mono<Void> handle(WebSocketSession session) {
 								switch (message.resolvedType()) {
 									case NEXT -> graphQlSession.handleNext(message);
 									case PING -> graphQlSession.sendPong(null);
+									case PONG -> { }
 									case ERROR -> graphQlSession.handleError(message);
 									case COMPLETE -> graphQlSession.handleComplete(message);
 									default -> throw new IllegalStateException(
@@ -290,10 +303,21 @@ public Mono<Void> handle(WebSocketSession session) {
 							}
 						}
 						return Mono.empty();
-					})
-					.then();
+					});
+
+			if (keepalive > 0) {
+				Duration keepAliveDuration = Duration.ofSeconds(keepalive);
+				receiveCompletion = receiveCompletion
+						.mergeWith(Flux.interval(keepAliveDuration, keepAliveDuration)
+							.flatMap(i -> {
+								graphQlSession.sendPing(null);
+								return Mono.empty();
+							})
+						);
+			}
+
 
-			return Mono.zip(sendCompletion, receiveCompletion).then();
+			return Mono.zip(sendCompletion, receiveCompletion.then()).then();
 		}
 
 		private boolean sessionNotInitialized() {
@@ -459,6 +483,11 @@ void sendPong(@Nullable Map<String, Object> payload) {
 			this.requestSink.sendRequest(message);
 		}
 
+		public void sendPing(@Nullable Map<String, Object> payload) {
+			GraphQlWebSocketMessage message = GraphQlWebSocketMessage.ping(payload);
+			this.requestSink.sendRequest(message);
+		}
+
 
 		// Inbound messages
 

spring-graphql/src/test/java/org/springframework/graphql/client/MockGraphQlWebSocketServer.java

@@ -110,6 +110,9 @@ private Publisher<GraphQlWebSocketMessage> handleMessage(GraphQlWebSocketMessage
 										GraphQlWebSocketMessage.error(id, Collections.singletonList(request.getError())) :
 										GraphQlWebSocketMessage.complete(id));
 			}
+			case PING -> {
+				return Mono.just(GraphQlWebSocketMessage.pong(null));
+			}
 			case COMPLETE -> {
 				return Flux.empty();
 			}

spring-graphql/src/test/java/org/springframework/graphql/client/WebSocketGraphQlTransportTests.java

@@ -60,6 +60,7 @@ public class WebSocketGraphQlTransportTests {
 	private static final Duration TIMEOUT = Duration.ofSeconds(5);
 
 	private static final CodecDelegate CODEC_DELEGATE = new CodecDelegate(ClientCodecConfigurer.create());
+	public static final int KEEPALIVE = 1;
 
 
 	private final MockGraphQlWebSocketServer mockServer = new MockGraphQlWebSocketServer();
@@ -185,6 +186,22 @@ void pingHandling() {
 				GraphQlWebSocketMessage.subscribe("1", new DefaultGraphQlRequest("{Query1}")));
 	}
 
+	@Test
+	void pingSending() throws InterruptedException {
+
+		GraphQlRequest request = this.mockServer.expectOperation("{Sub1}").andStream(Flux.just(this.response1, response2));
+
+		StepVerifier.create(this.transport.executeSubscription(request))
+				.expectNext(this.response1, response2).expectComplete()
+				.verify(TIMEOUT);
+		Thread.sleep(KEEPALIVE*1000 + 50); // wait for ping
+
+		assertActualClientMessages(
+				GraphQlWebSocketMessage.connectionInit(null),
+				GraphQlWebSocketMessage.subscribe("1", request),
+				GraphQlWebSocketMessage.ping(null));
+	}
+
 	@Test
 	void start() {
 		MockGraphQlWebSocketServer handler = new MockGraphQlWebSocketServer();
@@ -210,7 +227,7 @@ public Mono<Void> handleConnectionAck(Map<String, Object> ackPayload) {
 
 
 		WebSocketGraphQlTransport transport = new WebSocketGraphQlTransport(
-				URI.create("/"), HttpHeaders.EMPTY, client, ClientCodecConfigurer.create(), interceptor);
+				URI.create("/"), HttpHeaders.EMPTY, client, ClientCodecConfigurer.create(), interceptor, KEEPALIVE);
 
 		transport.start().block(TIMEOUT);
 
@@ -324,7 +341,7 @@ void errorDuringResponseHandling() {
 	private static WebSocketGraphQlTransport createTransport(WebSocketClient client) {
 		return new WebSocketGraphQlTransport(
 				URI.create("/"), HttpHeaders.EMPTY, client, ClientCodecConfigurer.create(),
-				new WebSocketGraphQlClientInterceptor() { });
+				new WebSocketGraphQlClientInterceptor() { }, KEEPALIVE);
 	}
 
 	private void assertActualClientMessages(GraphQlWebSocketMessage... expectedMessages) {