Expose values added by logback mdc instrumentation to the appender instrumentation (#14904)

Author: laurit

instrumentation/logback/logback-appender-1.0/javaagent/build.gradle.kts

@@ -46,6 +46,8 @@ dependencies {
 
   implementation(project(":instrumentation:logback:logback-appender-1.0:library"))
 
+  testInstrumentation(project(":instrumentation:logback:logback-mdc-1.0:javaagent"))
+
   testImplementation("org.awaitility:awaitility")
 }
 

instrumentation/logback/logback-appender-1.0/javaagent/src/test/java/io/opentelemetry/instrumentation/logback/appender/v1_0/LogbackTest.java

@@ -17,6 +17,7 @@
 import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.logs.Severity;
 import io.opentelemetry.api.trace.SpanContext;
+import io.opentelemetry.api.trace.TraceFlags;
 import io.opentelemetry.instrumentation.testing.junit.AgentInstrumentationExtension;
 import io.opentelemetry.instrumentation.testing.junit.InstrumentationExtension;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
@@ -167,6 +168,15 @@ private static void test(
                       satisfies(
                           EXCEPTION_STACKTRACE, v -> v.contains(LogbackTest.class.getName()))));
             }
+            if (withParent) {
+              SpanContext spanContext = testing.spans().get(0).getSpanContext();
+              attributeAsserts.addAll(
+                  Arrays.asList(
+                      equalTo(AttributeKey.stringKey("trace_id"), spanContext.getTraceId()),
+                      equalTo(AttributeKey.stringKey("span_id"), spanContext.getSpanId()),
+                      equalTo(
+                          AttributeKey.stringKey("trace_flags"), TraceFlags.getSampled().asHex())));
+            }
             logRecord.hasAttributesSatisfyingExactly(attributeAsserts);
           });
     } else {

instrumentation/logback/logback-mdc-1.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/logback/mdc/v1_0/LogbackMdcInstrumentationModule.java

@@ -29,4 +29,11 @@ public List<TypeInstrumentation> typeInstrumentations() {
   public boolean isIndyReady() {
     return true;
   }
+
+  @Override
+  public int order() {
+    // run before logback appender instrumentation so that the appender instrumentation can observe
+    // the attributes added to the mdc by this instrumentation
+    return -1;
+  }
 }