Send host.name in all spans

extensions/opentelemetry/deployment/src/test/java/io/quarkus/opentelemetry/deployment/OpenTelemetryResourceTest.java

@@ -4,6 +4,7 @@
 import static io.quarkus.opentelemetry.deployment.common.TestSpanExporter.getSpanByKindAndParentId;
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 import java.util.List;
 
@@ -54,6 +55,7 @@ void resource() {
         assertEquals("authservice", server.getResource().getAttribute(AttributeKey.stringKey("service.name")));
         assertEquals(config.getRawValue("quarkus.uuid"),
                 server.getResource().getAttribute(AttributeKey.stringKey("service.instance.id")));
+        assertNotNull(server.getResource().getAttribute(AttributeKey.stringKey("host.name")));
     }
 
     @Path("/hello")

extensions/opentelemetry/runtime/src/main/java/io/quarkus/opentelemetry/runtime/AutoConfiguredOpenTelemetrySdkBuilderCustomizer.java

@@ -3,6 +3,8 @@
 import static java.lang.Boolean.TRUE;
 import static java.util.Collections.emptyList;
 
+import java.net.InetAddress;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.function.BiFunction;
@@ -71,12 +73,21 @@ public Resource apply(Resource existingResource, ConfigProperties configProperti
                                 .filter(sn -> !sn.equals(appConfig.name.orElse("unset")))
                                 .orElse(null);
 
+                        // must be resolved at startup, once.
+                        String hostname = null;
+                        try {
+                            hostname = InetAddress.getLocalHost().getHostName();
+                        } catch (UnknownHostException e) {
+                            hostname = "unknown";
+                        }
+
                         // Merge resource instances with env attributes
                         Resource resource = resources.stream()
                                 .reduce(Resource.empty(), Resource::merge)
                                 .merge(TracerUtil.mapResourceAttributes(
                                         oTelRuntimeConfig.resourceAttributes().orElse(emptyList()),
-                                        serviceName)); // from properties
+                                        serviceName, // from properties
+                                        hostname));
                         return consolidatedResource.merge(resource);
                     } else {
                         return Resource.builder().build();

extensions/opentelemetry/runtime/src/main/java/io/quarkus/opentelemetry/runtime/tracing/TracerUtil.java

@@ -1,5 +1,6 @@
 package io.quarkus.opentelemetry.runtime.tracing;
 
+import static io.opentelemetry.semconv.resource.attributes.ResourceAttributes.HOST_NAME;
 import static io.opentelemetry.semconv.resource.attributes.ResourceAttributes.SERVICE_NAME;
 
 import java.util.List;
@@ -14,7 +15,7 @@ public class TracerUtil {
     private TracerUtil() {
     }
 
-    public static Resource mapResourceAttributes(List<String> resourceAttributes, String serviceName) {
+    public static Resource mapResourceAttributes(List<String> resourceAttributes, String serviceName, String hostname) {
         final AttributesBuilder attributesBuilder = Attributes.builder();
 
         if (!resourceAttributes.isEmpty()) {
@@ -27,6 +28,10 @@ public static Resource mapResourceAttributes(List<String> resourceAttributes, St
             attributesBuilder.put(SERVICE_NAME.getKey(), serviceName);
         }
 
+        if (hostname != null) {
+            attributesBuilder.put(HOST_NAME, hostname);
+        }
+
         return Resource.create(attributesBuilder.build());
     }
 }

extensions/opentelemetry/runtime/src/test/java/io/quarkus/opentelemetry/runtime/tracing/TracerUtilTest.java

@@ -19,7 +19,7 @@ public void testMapResourceAttributes() {
                 "service.namespace=mynamespace",
                 "service.version=1.0",
                 "deployment.environment=production");
-        Resource resource = TracerUtil.mapResourceAttributes(resourceAttributes, null);
+        Resource resource = TracerUtil.mapResourceAttributes(resourceAttributes, null, null);
         Attributes attributes = resource.getAttributes();
         Assertions.assertThat(attributes.size()).isEqualTo(4);
         Assertions.assertThat(attributes.get(ResourceAttributes.SERVICE_NAME)).isEqualTo("myservice");