Check for blocked instrumentation in tests

If there is a blocked instrumentation, the test will fail and the
failure message will include the same information that is logged
from MuzzleCheck.

Author: deejgregor

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/muzzle/MuzzleCheck.java

@@ -3,14 +3,19 @@
 import datadog.trace.agent.tooling.InstrumenterModule;
 import datadog.trace.agent.tooling.InstrumenterState;
 import datadog.trace.agent.tooling.Utils;
+import java.util.Collections;
 import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
 import net.bytebuddy.matcher.ElementMatcher;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 public class MuzzleCheck implements ElementMatcher<ClassLoader> {
   private static final Logger log = LoggerFactory.getLogger(MuzzleCheck.class);
 
+  private static final List<String> ERRORS = new CopyOnWriteArrayList<>();
+  private static volatile boolean recordErrors = false;
+
   private final int instrumentationId;
   private final String instrumentationClass;
   private final ReferenceProvider runtimeMuzzleReferences;
@@ -33,9 +38,13 @@ public boolean matches(ClassLoader classLoader) {
       InstrumenterState.applyInstrumentation(classLoader, instrumentationId);
     } else {
       InstrumenterState.blockInstrumentation(classLoader, instrumentationId);
-      if (log.isDebugEnabled()) {
+      if (recordErrors || log.isDebugEnabled()) {
         final List<Reference.Mismatch> mismatches =
             muzzle.getMismatchedReferenceSources(classLoader);
+        if (recordErrors) {
+          recordMuzzleMismatch(
+              InstrumenterState.describe(instrumentationId), classLoader, mismatches);
+        }
         log.debug(
             "Muzzled - {} instrumentation.target.classloader={}",
             InstrumenterState.describe(instrumentationId),
@@ -61,4 +70,38 @@ private ReferenceMatcher muzzle() {
     }
     return muzzle;
   }
+
+  /**
+   * Record a muzzle mismatch error for test visibility.
+   *
+   * @param instrumentationDescription the description of the instrumentation that was blocked
+   * @param classLoader the classloader where the instrumentation was blocked
+   * @param mismatches the list of mismatch details
+   */
+  private static void recordMuzzleMismatch(
+      String instrumentationDescription,
+      ClassLoader classLoader,
+      List<Reference.Mismatch> mismatches) {
+    StringBuilder sb = new StringBuilder();
+    sb.append("Muzzled - ")
+        .append(instrumentationDescription)
+        .append(" instrumentation.target.classloader=")
+        .append(classLoader)
+        .append("\n");
+    for (Reference.Mismatch mismatch : mismatches) {
+      sb.append("  Mismatch: ").append(mismatch).append("\n");
+    }
+    ERRORS.add(sb.toString());
+  }
+
+  // Visible for testing
+  public static void enableRecordingAndReset() {
+    recordErrors = true;
+    ERRORS.clear();
+  }
+
+  // Visible for testing
+  public static List<String> getErrors() {
+    return Collections.unmodifiableList(ERRORS);
+  }
 }

dd-java-agent/instrumentation-testing/src/main/groovy/datadog/trace/agent/test/InstrumentationSpecification.groovy

@@ -39,6 +39,7 @@ import datadog.trace.agent.tooling.InstrumenterModule
 import datadog.trace.agent.tooling.TracerInstaller
 import datadog.trace.agent.tooling.bytebuddy.matcher.ClassLoaderMatchers
 import datadog.trace.agent.tooling.bytebuddy.matcher.GlobalIgnores
+import datadog.trace.agent.tooling.muzzle.MuzzleCheck
 import datadog.trace.api.Config
 import datadog.trace.api.IdGenerationStrategy
 import datadog.trace.api.Pair
@@ -478,6 +479,7 @@ abstract class InstrumentationSpecification extends DDSpecification implements A
       ActiveSubsystems.APPSEC_ACTIVE = true
     }
     InstrumentationErrors.enableRecordingAndReset()
+    MuzzleCheck.enableRecordingAndReset()
     ProcessTags.reset()
   }
 
@@ -521,6 +523,8 @@ abstract class InstrumentationSpecification extends DDSpecification implements A
     }
     def instrumentationErrorCount = InstrumentationErrors.getErrors().size()
     assert instrumentationErrorCount == 0, "${instrumentationErrorCount} instrumentation errors were seen:\n${InstrumentationErrors.getErrors().join("\n---\n")}"
+    def muzzleErrorCount = MuzzleCheck.getErrors().size()
+    assert muzzleErrorCount == 0, "${muzzleErrorCount} muzzle errors were seen:\n${MuzzleCheck.getErrors().join("\n---\n")}"
   }
 
   private void doCheckRepeatedFinish() {