Fixed problem in AUTO_FLUSH backpressure strategy (helidon-io#6556)

* Fixed problem in AUTO_FLUSH strategy that may result in pub-sub deadlock. Increment buffer sum before checking watermark and flushing.

* Generate large binary file programmatically.

Signed-off-by: Santiago Pericasgeertsen <[email protected]>

* Use constant.

Signed-off-by: Santiago Pericasgeertsen <[email protected]>

---------

Signed-off-by: Santiago Pericasgeertsen <[email protected]>

microprofile/server/src/test/java/io/helidon/microprofile/server/AutoFlushTest.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2023 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.microprofile.server;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import io.helidon.common.http.Http;
+import io.helidon.microprofile.tests.junit5.AddBean;
+import io.helidon.microprofile.tests.junit5.HelidonTest;
+import jakarta.inject.Inject;
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.client.WebTarget;
+import jakarta.ws.rs.core.Response;
+import jakarta.ws.rs.core.StreamingOutput;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@HelidonTest
+@AddBean(AutoFlushTest.AutoFlushResource.class)
+class AutoFlushTest {
+
+    private static File file;
+    private static final int FILE_SIZE = 6000000;
+
+    @Inject
+    private WebTarget target;
+
+    @Path("auto-flush")
+    public static class AutoFlushResource {
+
+        @GET
+        public Response getDefaultMessage() {
+            return Response.ok((StreamingOutput) outputStream -> {
+                try (InputStream is = new FileInputStream(file)) {
+                    is.transferTo(outputStream);
+                }
+            }).header(Http.Header.CONTENT_LENGTH, String.valueOf(FILE_SIZE)).build();
+        }
+    }
+
+    @BeforeAll
+    static void createTempFile() throws IOException {
+        file = File.createTempFile("zero", ".bin");
+        file.deleteOnExit();
+        byte[] zero = new byte[10 * 1000];
+        try (FileOutputStream fos = new FileOutputStream(file)) {
+            for (int i = 0; i < FILE_SIZE / zero.length; i++) {
+                fos.write(zero);
+            }
+        }
+    }
+
+    @Test
+    void testAutoFlush() {
+        try (Response resp = target.path("auto-flush")
+                .request()
+                .get()) {
+            assertThat(resp.getStatus(), is(200));
+            assertThat(resp.getHeaderString(Http.Header.CONTENT_LENGTH), is(String.valueOf(FILE_SIZE)));
+            assertThat(resp.readEntity(byte[].class).length, is(FILE_SIZE));
+        }
+    }
+}

webserver/webserver/src/main/java/io/helidon/webserver/ServerResponseSubscription.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Oracle and/or its affiliates.
+ * Copyright (c) 2022, 2023 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -120,10 +120,10 @@ class WatermarkAutoFlush extends WatermarkLinear {
 
         @Override
         public void inc(NettyChannel channel, int byteSize) {
+            super.inc(channel, byteSize);
             if (!watermarkNotReached()) {
                 channel.flush();
             }
-            super.inc(channel, byteSize);
         }
     }