Support OTEL_SERVICE_NAME (#353)

* Support OTEL_SERVICE_NAME

* spotless

README.md

@@ -103,7 +103,7 @@ Then the runtime parameters would be updated to:
 
 ```bash
 java -javaagent:./splunk-otel-javaagent.jar \
-     -Dotel.resource.attributes=service.name=my-java-app \
+     -Dotel.service.name=my-java-app \
      -jar myapp.jar https://splunk.com
 ```
 
@@ -121,9 +121,9 @@ To see the Java Agent in action with sample applications, see our
 
 ### Basic Configuration
 
-The service name resource attribute is the only configuration option
-that needs to be specified. You can set it by adding a `service.name`
-attribute as shown in the [example above](#getting-started).
+The service name is the only configuration option that is required. You can
+specify it by setting the `otel.service.name` system property as shown in the
+[example above](#getting-started).
 
 A few other configuration options that may need to be changed or set are:
 
@@ -139,12 +139,12 @@ A few other configuration options that may need to be changed or set are:
 - Environment resource attribute `deployment.environment` to specify what
   environment the span originated from. For example:
   ```
-  -Dotel.resource.attributes=service.name=my-java-app,deployment.environment=production
+  -Dotel.resource.attributes=deployment.environment=production
   ```
 - Service version resource attribute `service.version` to specify the version
   of your instrumented application. For example:
   ```
-  -Dotel.resource.attributes=service.name=my-java-app,service.version=1.2.3
+  -Dotel.resource.attributes=deployment.environment=production,service.version=1.2.3
   ```
 
 The `deployment.environment` and `service.version` resource attributes are not

custom/src/main/java/com/splunk/opentelemetry/ServiceNameChecker.java

@@ -21,22 +21,46 @@
 import io.opentelemetry.javaagent.extension.AgentListener;
 import io.opentelemetry.semconv.resource.attributes.ResourceAttributes;
 import java.util.Map;
+import java.util.function.Consumer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 @AutoService(AgentListener.class)
 public class ServiceNameChecker implements AgentListener {
   private static final Logger log = LoggerFactory.getLogger(ServiceNameChecker.class);
 
+  private final Consumer<String> logWarn;
+
+  public ServiceNameChecker() {
+    this(log::warn);
+  }
+
+  // visible for tests
+  ServiceNameChecker(Consumer<String> logWarn) {
+    this.logWarn = logWarn;
+  }
+
   @Override
   public void beforeAgent(Config config) {
-    Map<String, String> resourceAttributes = config.getMapProperty("otel.resource.attributes");
-    if (!resourceAttributes.containsKey(ResourceAttributes.SERVICE_NAME.getKey())) {
-      log.warn(
+    if (serviceNameNotConfigured(config)) {
+      logWarn.accept(
           "Resource attribute 'service.name' is not set: your service is unnamed and will be difficult to identify."
               + " Please Set your service name using the 'OTEL_RESOURCE_ATTRIBUTES' environment variable"
               + " or the 'otel.resource.attributes' system property."
               + " E.g. 'export OTEL_RESOURCE_ATTRIBUTES=\"service.name=<YOUR_SERVICE_NAME_HERE>\"'");
     }
   }
+
+  // make sure this listener is one of the first things run by the agent
+  @Override
+  public int order() {
+    return -100;
+  }
+
+  private static boolean serviceNameNotConfigured(Config config) {
+    String serviceName = config.getProperty("otel.service.name");
+    Map<String, String> resourceAttributes = config.getMapProperty("otel.resource.attributes");
+    return serviceName == null
+        && !resourceAttributes.containsKey(ResourceAttributes.SERVICE_NAME.getKey());
+  }
 }

custom/src/test/java/com/splunk/opentelemetry/ServiceNameCheckerTest.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * 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 com.splunk.opentelemetry;
+
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+import io.opentelemetry.instrumentation.api.config.Config;
+import java.util.Map;
+import java.util.function.Consumer;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class ServiceNameCheckerTest {
+  @Mock Consumer<String> logWarn;
+
+  @Test
+  void shouldLogWarnWhenNeitherServiceNameNorResourceAttributeIsConfigured() {
+    // given
+    var config = Config.newBuilder().build();
+
+    var underTest = new ServiceNameChecker(logWarn);
+
+    // when
+    underTest.beforeAgent(config);
+
+    // then
+    verify(logWarn).accept(anyString());
+  }
+
+  @Test
+  void shouldNotLogWarnWhenServiceNameIsConfigured() {
+    // given
+    var config = Config.newBuilder().readProperties(Map.of("otel.service.name", "test")).build();
+
+    var underTest = new ServiceNameChecker(logWarn);
+
+    // when
+    underTest.beforeAgent(config);
+
+    // then
+    verifyNoInteractions(logWarn);
+  }
+
+  @Test
+  void shouldNotLogWarnWhenResourceAttributeIsConfigured() {
+    // given
+    var config =
+        Config.newBuilder()
+            .readProperties(Map.of("otel.resource.attributes", "service.name=test"))
+            .build();
+
+    var underTest = new ServiceNameChecker(logWarn);
+
+    // when
+    underTest.beforeAgent(config);
+
+    // then
+    verifyNoInteractions(logWarn);
+  }
+}

docs/advanced-config.md

@@ -78,6 +78,7 @@ export OTEL_PROPAGATORS=b3multi
 | `otel.instrumentation.methods.include`                           | `OTEL_INSTRUMENTATION_METHODS_INCLUDE`                           | unset         | Stable  | Same as adding `@WithSpan` annotation functionality for the target method string. <details><summary>Format</summary>`my.package.MyClass1[method1,method2];my.package.MyClass2[method3]`</details>
 | `otel.instrumentation.opentelemetry-annotations.exclude-methods` | `OTEL_INSTRUMENTATION_OPENTELEMETRY_ANNOTATIONS_EXCLUDE_METHODS` | unset         | Stable  | Suppress `@WithSpan` instrumentation for specific methods. <details><summary>Format</summary>`my.package.MyClass1[method1,method2];my.package.MyClass2[method3]`</details>
 | `otel.resource.attributes`                                       | `OTEL_RESOURCE_ATTRIBUTES`                                       | unset         | Stable  | Comma-separated list of resource attributes added to every reported span. <details><summary>Example</summary>`key1=val1,key2=val2`</details>
+| `otel.service.name`                                              | `OTEL_SERVICE_NAME`                                              | unset         | Stable  | Sets the value of the `service.name` resource attribute. If `service.name` is also set in `otel.resource.attributes`, this setting takes precedence.
 | `otel.span.attribute.count.limit`                                | `OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT`                                | unlimited     | Stable  | Maximum number of attributes per span.
 | `otel.span.event.count.limit`                                    | `OTEL_SPAN_EVENT_COUNT_LIMIT`                                    | unlimited     | Stable  | Maximum number of events per span.
 | `otel.span.link.count.limit`                                     | `OTEL_SPAN_LINK_COUNT_LIMIT`                                     | `1000`        | Stable  | Maximum number of links per span.