Ensures gRPC client calls pass metadata as headers (#10301)

Ensures gRPC client calls pass metadata as headers. Moves utility class from webserver-grpc to grpc-core. Adds test that shows headers and metadata properly merged in a client call.

Author: spericas

grpc/core/pom.xml

@@ -41,6 +41,10 @@
             <groupId>io.helidon.http</groupId>
             <artifactId>helidon-http</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.helidon.http</groupId>
+            <artifactId>helidon-http-http2</artifactId>
+        </dependency>
         <dependency>
             <groupId>io.helidon.tracing</groupId>
             <artifactId>helidon-tracing</artifactId>
@@ -77,5 +81,10 @@
             <artifactId>hamcrest-all</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

webserver/grpc/src/main/java/io/helidon/webserver/grpc/GrpcHeadersUtil.java renamed to grpc/core/src/main/java/io/helidon/grpc/core/GrpcHeadersUtil.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.helidon.webserver.grpc;
+package io.helidon.grpc.core;
 
 import java.util.Base64;
 
@@ -26,12 +26,21 @@
 
 import static java.nio.charset.StandardCharsets.US_ASCII;
 
-class GrpcHeadersUtil {
+/**
+ * Utility class to map HTTP/2 headers to Metadata.
+ */
+public class GrpcHeadersUtil {
 
     private GrpcHeadersUtil() {
     }
 
-    static void updateHeaders(WritableHeaders<?> headers, Metadata metadata) {
+    /**
+     * Updates headers with metadata.
+     *
+     * @param headers the headers to update
+     * @param metadata the metadata
+     */
+    public static void updateHeaders(WritableHeaders<?> headers, Metadata metadata) {
         Base64.Encoder encoder = Base64.getEncoder();
         metadata.keys().forEach(name -> {
             if (name.endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
@@ -48,7 +57,13 @@ static void updateHeaders(WritableHeaders<?> headers, Metadata metadata) {
         });
     }
 
-    static Metadata toMetadata(Http2Headers headers) {
+    /**
+     * Converts a set of HTTP/2 headers into a Metadata instance.
+     *
+     * @param headers the headers to convert
+     * @return the new metadata
+     */
+    public static Metadata toMetadata(Http2Headers headers) {
         Base64.Decoder decoder = Base64.getDecoder();
         Metadata metadata = new Metadata();
         headers.httpHeaders().forEach(header -> {

grpc/core/src/main/java/module-info.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024 Oracle and/or its affiliates.
+ * Copyright (c) 2022, 2025 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.
@@ -21,6 +21,7 @@
 
     requires io.helidon.common;
     requires io.helidon.http;
+    requires io.helidon.http.http2;
     requires io.helidon.common.context;
     requires io.helidon.tracing;
 

webserver/grpc/src/test/java/io/helidon/webserver/grpc/GrpcHeadersUtilTest.java renamed to grpc/core/src/test/java/io/helidon/grpc/core/GrpcHeadersUtilTest.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.helidon.webserver.grpc;
+package io.helidon.grpc.core;
 
 import java.util.HashSet;
 import java.util.List;

webclient/grpc/src/main/java/io/helidon/webclient/grpc/GrpcBaseClientCall.java

@@ -31,6 +31,7 @@
 import io.helidon.common.LazyValue;
 import io.helidon.common.buffers.BufferData;
 import io.helidon.common.socket.HelidonSocket;
+import io.helidon.grpc.core.GrpcHeadersUtil;
 import io.helidon.http.Header;
 import io.helidon.http.HeaderNames;
 import io.helidon.http.HeaderValues;
@@ -175,16 +176,22 @@ public Duration readTimeout() {
         startStreamingThreads();
 
         // send HEADERS frame
-        WritableHeaders<?> headers = WritableHeaders.create();
-        headers.add(Http2Headers.AUTHORITY_NAME, clientUri.authority());
-        headers.add(Http2Headers.METHOD_NAME, "POST");
-        headers.add(Http2Headers.PATH_NAME, "/" + methodDescriptor.getFullMethodName());
-        headers.add(Http2Headers.SCHEME_NAME, "http");
-        headers.add(GRPC_CONTENT_TYPE);
-        headers.add(GRPC_ACCEPT_ENCODING);
+        WritableHeaders<?> headers = setupHeaders(metadata, clientUri.authority(), methodDescriptor.getFullMethodName());
         clientStream.writeHeaders(Http2Headers.create(headers), false);
     }
 
+    static WritableHeaders<?> setupHeaders(Metadata metadata, String authority, String methodName) {
+        WritableHeaders<?> headers = WritableHeaders.create();
+        GrpcHeadersUtil.updateHeaders(headers, metadata);
+        headers.set(Http2Headers.AUTHORITY_NAME, authority);
+        headers.set(Http2Headers.METHOD_NAME, "POST");
+        headers.set(Http2Headers.PATH_NAME, "/" + methodName);
+        headers.set(Http2Headers.SCHEME_NAME, "http");
+        headers.set(GRPC_CONTENT_TYPE);
+        headers.set(GRPC_ACCEPT_ENCODING);
+        return headers;
+    }
+
     abstract void startStreamingThreads();
 
     /**

webclient/grpc/src/test/java/io/helidon/webclient/grpc/GrpcBaseClientCallTest.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2025 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.webclient.grpc;
+
+import io.helidon.http.HeaderNames;
+import io.helidon.http.WritableHeaders;
+import io.helidon.http.http2.Http2Headers;
+
+import io.grpc.Metadata;
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.greaterThan;
+
+class GrpcBaseClientCallTest {
+
+    @Test
+    void testHeadersAndMetadata() {
+        Metadata metadata = new Metadata();
+        Metadata.Key<String> key = Metadata.Key.of("cookie", Metadata.ASCII_STRING_MARSHALLER);
+        metadata.put(key, "sugar");
+        WritableHeaders<?> headers = GrpcBaseClientCall.setupHeaders(metadata, "localhost", "foo");
+        assertThat(headers.size(), greaterThan(2));
+        assertThat(headers.get(Http2Headers.AUTHORITY_NAME).get(), is("localhost"));
+        assertThat(headers.get(Http2Headers.METHOD_NAME).get(), is("POST"));
+        assertThat(headers.get(Http2Headers.PATH_NAME).get(), is("/foo"));
+        assertThat(headers.get(Http2Headers.SCHEME_NAME).get(), is("http"));
+        assertThat(headers.get(HeaderNames.COOKIE).get(), is("sugar"));
+    }
+}

webserver/grpc/pom.xml

@@ -86,11 +86,6 @@
             <artifactId>hamcrest-all</artifactId>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>org.mockito</groupId>
-            <artifactId>mockito-core</artifactId>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
     <build>

webserver/grpc/src/main/java/io/helidon/webserver/grpc/GrpcProtocolHandler.java

@@ -31,6 +31,7 @@
 
 import io.helidon.common.LazyValue;
 import io.helidon.common.buffers.BufferData;
+import io.helidon.grpc.core.GrpcHeadersUtil;
 import io.helidon.http.Header;
 import io.helidon.http.HeaderName;
 import io.helidon.http.HeaderNames;