When using SSE send the headers (and flush them) as soon as we have t…

…he Publisher (so before subscription). Fix quarkusio#22762 (cherry picked from commit 23ab5a0)
gsmet · Feb 21, 2022 · 03ad7cf · 03ad7cf
1 parent ddd0f35
commit 03ad7cf
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Showing 3 changed files with 22 additions and 9 deletions.
diff --git a/...eactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java b/...eactive/server/runtime/src/main/java/org/jboss/resteasy/reactive/server/core/SseUtil.java
@@ -151,8 +151,6 @@ public static void setHeaders(ResteasyReactiveRequestContext context, ServerHttp
 
     public static void setHeaders(ResteasyReactiveRequestContext context, ServerHttpResponse response,
             List<PublisherResponseHandler.StreamingResponseCustomizer> customizers) {
-        // FIXME: spec says we should flush the headers when first message is sent or when the resource method returns, whichever
-        // happens first
         if (!response.headWritten()) {
             response.setStatusCode(Response.Status.OK.getStatusCode());
             response.setResponseHeader(HttpHeaders.CONTENT_TYPE, MediaType.SERVER_SENT_EVENTS);
@@ -164,6 +162,7 @@ public static void setHeaders(ResteasyReactiveRequestContext context, ServerHttp
                 customizers.get(i).customize(response);
             }
             // FIXME: other headers?
+
         }
     }
 }
diff --git a/...e/src/main/java/org/jboss/resteasy/reactive/server/handlers/PublisherResponseHandler.java b/...e/src/main/java/org/jboss/resteasy/reactive/server/handlers/PublisherResponseHandler.java
@@ -1,10 +1,14 @@
 package org.jboss.resteasy.reactive.server.handlers;
 
+import static org.jboss.resteasy.reactive.server.jaxrs.SseEventSinkImpl.EMPTY_BUFFER;
+
 import java.nio.charset.StandardCharsets;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
+import java.util.function.Consumer;
 import javax.ws.rs.core.MediaType;
 import org.jboss.logging.Logger;
 import org.jboss.resteasy.reactive.server.core.ResteasyReactiveRequestContext;
@@ -40,9 +44,9 @@ private static class SseMultiSubscriber extends AbstractMultiSubscriber {
         @Override
         public void onNext(Object item) {
             OutboundSseEventImpl event = new OutboundSseEventImpl.BuilderImpl().data(item).build();
-            SseUtil.send(requestContext, event, customizers).handle(new BiFunction<Object, Throwable, Object>() {
+            SseUtil.send(requestContext, event, customizers).whenComplete(new BiConsumer<Object, Throwable>() {
                 @Override
-                public Object apply(Object v, Throwable t) {
+                public void accept(Object v, Throwable t) {
                     if (t != null) {
                         // need to cancel because the exception didn't come from the Multi
                         subscription.cancel();
@@ -51,7 +55,6 @@ public Object apply(Object v, Throwable t) {
                         // send in the next item
                         subscription.request(1);
                     }
-                    return null;
                 }
             });
         }
@@ -204,11 +207,11 @@ public void handle(ResteasyReactiveRequestContext requestContext) throws Excepti
             requestContext.setResponseContentType(mediaTypes[0]);
             // this is the non-async return type
             requestContext.setGenericReturnType(requestContext.getTarget().getReturnType());
-            // we have several possibilities here, but in all we suspend
-            requestContext.suspend();
+
             if (mediaTypes[0].isCompatible(MediaType.SERVER_SENT_EVENTS_TYPE)) {
                 handleSse(requestContext, result);
             } else {
+                requestContext.suspend();
                 boolean json = mediaTypes[0].isCompatible(MediaType.APPLICATION_JSON_TYPE);
                 handleStreaming(requestContext, result, json);
             }
@@ -220,7 +223,18 @@ private void handleStreaming(ResteasyReactiveRequestContext requestContext, Publ
     }
 
     private void handleSse(ResteasyReactiveRequestContext requestContext, Publisher<?> result) {
-        result.subscribe(new SseMultiSubscriber(requestContext, streamingResponseCustomizers));
+        SseUtil.setHeaders(requestContext, requestContext.serverResponse(), streamingResponseCustomizers);
+        requestContext.suspend();
+        requestContext.serverResponse().write(EMPTY_BUFFER, new Consumer<Throwable>() {
+            @Override
+            public void accept(Throwable throwable) {
+                if (throwable == null) {
+                    result.subscribe(new SseMultiSubscriber(requestContext, streamingResponseCustomizers));
+                } else {
+                    requestContext.resume(throwable);
+                }
+            }
+        });
     }
 
     public interface StreamingResponseCustomizer {

diff --git a/...rver/runtime/src/main/java/org/jboss/resteasy/reactive/server/jaxrs/SseEventSinkImpl.java b/...rver/runtime/src/main/java/org/jboss/resteasy/reactive/server/jaxrs/SseEventSinkImpl.java
@@ -11,7 +11,7 @@
 
 public class SseEventSinkImpl implements SseEventSink {
 
-    private static final byte[] EMPTY_BUFFER = new byte[0];
+    public static final byte[] EMPTY_BUFFER = new byte[0];
     private ResteasyReactiveRequestContext context;
     private SseBroadcasterImpl broadcaster;
     private boolean closed;