feat: add method to retrieve general instrumentation configuration by name

Author: zeitlinger

api/incubator/src/main/java/io/opentelemetry/api/incubator/config/ConfigProvider.java

@@ -48,6 +48,23 @@ default DeclarativeConfigProperties getJavaInstrumentationConfig(String name) {
     return config.getStructured("java", empty()).getStructured(name, empty());
   }
 
+  /**
+   * Returns the {@link DeclarativeConfigProperties} for general instrumentation config by name. If
+   * no configuration is available for the given name, an empty {@link DeclarativeConfigProperties}
+   * is returned.
+   *
+   * @param name the name of the general instrumentation config
+   * @return the {@link DeclarativeConfigProperties} for the given general instrumentation config
+   *     name
+   */
+  default DeclarativeConfigProperties getGeneralInstrumentationConfig(String name) {
+    DeclarativeConfigProperties config = getInstrumentationConfig();
+    if (config == null) {
+      return empty();
+    }
+    return config.getStructured("general", empty()).getStructured(name, empty());
+  }
+
   /** Returns a no-op {@link ConfigProvider}. */
   static ConfigProvider noop() {
     return () -> null;

api/incubator/src/test/java/io/opentelemetry/api/incubator/ConfigProviderTest.java

@@ -17,4 +17,12 @@ void noopEquality() {
     ConfigProvider noop = ConfigProvider.noop();
     assertThat(ConfigProvider.noop()).isSameAs(noop);
   }
+
+  @Test
+  void instrumentationConfigFallback() {
+    ConfigProvider configProvider = ConfigProvider.noop();
+    assertThat(configProvider.getInstrumentationConfig()).isNull();
+    assertThat(configProvider.getJavaInstrumentationConfig("servlet")).isNotNull();
+    assertThat(configProvider.getGeneralInstrumentationConfig("http")).isNotNull();
+  }
 }

sdk-extensions/autoconfigure/src/testIncubating/java/io/opentelemetry/sdk/autoconfigure/DeclarativeConfigurationTest.java

@@ -5,6 +5,7 @@
 
 package io.opentelemetry.sdk.autoconfigure;
 
+import static io.opentelemetry.api.incubator.config.DeclarativeConfigProperties.empty;
 import static io.opentelemetry.sdk.testing.assertj.OpenTelemetryAssertions.assertThat;
 import static java.util.Collections.singletonMap;
 import static org.assertj.core.api.Assertions.assertThatCode;
@@ -232,8 +233,14 @@ void configFile_ConfigProvider() {
         .isNotNull()
         .satisfies(exampleConfig -> assertThat(exampleConfig.getString("key")).isEqualTo("value"));
 
-    // shortcut to get specific instrumentation config
+    // shortcuts to get specific instrumentation config
     assertThat(globalConfigProvider.getJavaInstrumentationConfig("example").getString("key"))
         .isEqualTo("value");
+    assertThat(
+            globalConfigProvider
+                .getGeneralInstrumentationConfig("http")
+                .getStructured("client", empty())
+                .getScalarList("request_captured_headers", String.class))
+        .isEqualTo(Arrays.asList("Content-Type", "Accept"));
   }
 }