Adds support for HTTP health checks to gRPC example

examples/webserver/grpc/pom.xml

@@ -46,6 +46,10 @@
             <groupId>io.grpc</groupId>
             <artifactId>grpc-api</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.helidon.config</groupId>
+            <artifactId>helidon-config-yaml</artifactId>
+        </dependency>
         <dependency>
             <groupId>io.helidon.grpc</groupId>
             <artifactId>helidon-grpc-core</artifactId>
@@ -54,6 +58,14 @@
             <groupId>io.helidon.webserver</groupId>
             <artifactId>helidon-webserver-grpc</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.helidon.webserver.observe</groupId>
+            <artifactId>helidon-webserver-observe-health</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>io.helidon.health</groupId>
+            <artifactId>helidon-health-checks</artifactId>
+        </dependency>
         <dependency>
             <groupId>com.google.protobuf</groupId>
             <artifactId>protobuf-java</artifactId>

examples/webserver/grpc/src/main/java/io/helidon/examples/webserver/grpc/GrpcMain.java

@@ -16,9 +16,12 @@
 
 package io.helidon.examples.webserver.grpc;
 
+import io.helidon.config.Config;
 import io.helidon.logging.common.LogConfig;
 import io.helidon.webserver.WebServer;
 import io.helidon.webserver.grpc.GrpcRouting;
+import io.helidon.webserver.observe.ObserveFeature;
+import io.helidon.webserver.observe.health.HealthObserver;
 
 class GrpcMain {
 
@@ -33,9 +36,24 @@ private GrpcMain() {
     public static void main(String[] args) {
         LogConfig.configureRuntime();
 
+        // initialize global config from default configuration
+        Config config = Config.create();
+        Config.global(config);
+        Config serverConfig = config.get("server");
+
+        // create a health check to verify gRPC endpoint
+        ObserveFeature observe = ObserveFeature.builder()
+                .addObserver(HealthObserver.builder()
+                                     .details(true)
+                                     .addCheck(new StringServiceHealthCheck(serverConfig))
+                                     .build())
+                .build();
+
+        // start server and register gRPC routing and health check
         WebServer.builder()
-                .port(8080)
+                .config(serverConfig)
                 .addRouting(GrpcRouting.builder().service(new StringService()))
+                .addFeature(observe)
                 .build()
                 .start();
     }

examples/webserver/grpc/src/main/java/io/helidon/examples/webserver/grpc/StringServiceHealthCheck.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2024 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.examples.webserver.grpc;
+
+import io.helidon.common.configurable.Resource;
+import io.helidon.common.tls.Tls;
+import io.helidon.config.Config;
+import io.helidon.health.HealthCheck;
+import io.helidon.health.HealthCheckResponse;
+import io.helidon.health.HealthCheckType;
+import io.helidon.webclient.api.WebClient;
+import io.helidon.webclient.grpc.GrpcClient;
+
+class StringServiceHealthCheck implements HealthCheck {
+
+    private final WebClient webClient;
+
+    StringServiceHealthCheck(Config config) {
+        Tls clientTls = Tls.builder()
+                .trust(trust -> trust
+                        .keystore(store -> store
+                                .passphrase("password")
+                                .trustStore(true)
+                                .keystore(Resource.create("client.p12"))))
+                .build();
+        int serverPort = config.get("port").asInt().get();
+        this.webClient = WebClient.builder()
+                .tls(clientTls)
+                .baseUri("https://localhost:" + serverPort)
+                .build();
+    }
+
+    @Override
+    public String name() {
+        return StringService.class.getSimpleName();
+    }
+
+    @Override
+    public HealthCheckType type() {
+        return HealthCheckType.READINESS;
+    }
+
+    /**
+     * Self-invocation to verify gRPC endpoint is available and ready.
+     *
+     * @return health check response
+     */
+    @Override
+    public HealthCheckResponse call() {
+        try {
+            GrpcClient grpcClient = webClient.client(GrpcClient.PROTOCOL);
+            StringServiceGrpc.StringServiceBlockingStub service =
+                    StringServiceGrpc.newBlockingStub(grpcClient.channel());
+            Strings.StringMessage res = service.upper(
+                    Strings.StringMessage.newBuilder().setText("hello").build());
+            return HealthCheckResponse.builder()
+                    .status(res.getText().equals("HELLO"))
+                    .get();
+        } catch (Exception e) {
+            return HealthCheckResponse.builder()
+                    .status(false)
+                    .get();
+        }
+    }
+}

examples/webserver/grpc/src/main/resources/application.yaml

@@ -15,7 +15,7 @@
 #
 
 server:
-  port: 0
+  port: 8080
   tls:
     trust:
       keystore:
@@ -28,3 +28,8 @@ server:
         passphrase: "password"
         resource:
           resource-path: "server.p12"
+  features:
+    observe:
+      observers:
+        health:
+          details: true

examples/webserver/grpc/src/test/java/io/helidon/examples/webserver/grpc/StringServiceTest.java

@@ -26,6 +26,8 @@
 
 import io.helidon.common.configurable.Resource;
 import io.helidon.common.tls.Tls;
+import io.helidon.http.Status;
+import io.helidon.webclient.api.HttpClientResponse;
 import io.helidon.webclient.api.WebClient;
 import io.helidon.webclient.grpc.GrpcClient;
 import io.helidon.webserver.Router;
@@ -38,7 +40,9 @@
 import io.grpc.stub.StreamObserver;
 import org.junit.jupiter.api.Test;
 
+import static org.hamcrest.CoreMatchers.containsString;
 import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.not;
 import static org.hamcrest.MatcherAssert.assertThat;
 
 /**
@@ -132,6 +136,19 @@ void testUnaryUpperInterceptor() {
         assertThat(res.getText(), is("[[HELLO]]"));
     }
 
+    /**
+     * Tests server health using HTTP, not gRPC.
+     */
+    @Test
+    void testHealthHttp() {
+        try (HttpClientResponse res = webClient.get("/observe/health").request()) {
+            assertThat(res.status(), is(Status.OK_200));
+            String value = res.as(String.class);
+            assertThat(value, containsString("UP"));
+            assertThat(value, not(containsString("DOWN")));
+        }
+    }
+
     static Strings.StringMessage newStringMessage(String data) {
         return Strings.StringMessage.newBuilder().setText(data).build();
     }

examples/webserver/grpc/src/test/resources/application.yaml

@@ -28,6 +28,11 @@ server:
         passphrase: "password"
         resource:
           resource-path: "server.p12"
+  features:
+    observe:
+      observers:
+        health:
+          details: true
 
 grpc-client:
   poll-wait-time: PT30S