Remove safeMatch from element matcher and document bb cache class

dd-java-agent-ittests/src/test/groovy/datadog/trace/agent/integration/classloading/ClassLoadingTest.groovy

@@ -71,6 +71,7 @@ class ClassLoadingTest extends Specification {
 
     then:
     // ClassToInstrumentChild won't cause an additional getResource() because its TypeDescription is created from transformation bytes.
+    loader.count > 0
     loader.count == countAfterFirstLoad
   }
 

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/ByteBuddyElementMatchers.java

@@ -91,7 +91,7 @@ public class ByteBuddyElementMatchers {
       // in {@code getSuperClass} calls
       TypeDefinition typeDefinition = target;
       while (typeDefinition != null) {
-        if (safeMatches(typeDefinition.asGenericType())
+        if (matcher.matches(typeDefinition.asGenericType())
             || hasInterface(typeDefinition, checkedInterfaces)) {
           return true;
         }
@@ -100,15 +100,6 @@ public class ByteBuddyElementMatchers {
       return false;
     }
 
-    private boolean safeMatches(TypeDescription.Generic target) {
-      try {
-        return matcher.matches(target);
-      } catch (final Exception e) {
-        log.debug(matcher + ": Exception trying to get match generic type description:", e);
-      }
-      return false;
-    }
-
     private TypeDefinition safeGetSuperClass(final TypeDefinition typeDefinition) {
       try {
         return typeDefinition.getSuperClass();
@@ -129,7 +120,7 @@ public class ByteBuddyElementMatchers {
         final TypeDefinition typeDefinition, final Set<TypeDescription> checkedInterfaces) {
       for (final TypeDefinition interfaceType : safeGetInterfaces(typeDefinition)) {
         if (checkedInterfaces.add(interfaceType.asErasure())
-            && (safeMatch(interfaceType.asGenericType())
+            && (matcher.matches(interfaceType.asGenericType())
                 || hasInterface(interfaceType, checkedInterfaces))) {
           return true;
         }
@@ -137,15 +128,12 @@ public class ByteBuddyElementMatchers {
       return false;
     }
 
-    private boolean safeMatch(TypeDescription.Generic target) {
+    /**
-      try {
+     * TypeDefinition#getInterfaces() may throw an exception during iteration if an interface is
-        return matcher.matches(target);
+     * absent from the classpath.
-      } catch (final Exception e) {
+     *
-        log.debug(matcher + ": Exception while matching:", e);
+     * <p>This method exists to allow getting interfaces even if the lookup on one fails.
-      }
+     */
-      return false;
-    }
-
     private List<TypeDefinition> safeGetInterfaces(final TypeDefinition typeDefinition) {
       final List<TypeDefinition> interfaceTypes = new ArrayList<>();
       try {

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/DDCachingPoolStrategy.java

@@ -1,5 +1,6 @@
 package datadog.trace.agent.tooling;
 
+import static datadog.trace.agent.tooling.ClassLoaderMatcher.BOOTSTRAP_CLASSLOADER;
 import static net.bytebuddy.agent.builder.AgentBuilder.*;
 
 import java.util.Collections;
@@ -8,13 +9,27 @@ import java.util.WeakHashMap;
 import net.bytebuddy.dynamic.ClassFileLocator;
 import net.bytebuddy.pool.TypePool;
 
+/**
+ * Custom Pool strategy.
+ *
+ * <p>This is similar to: AgentBuilder.PoolStrategy.WithTypePoolCache.Simple(new
+ * MapMaker().weakKeys().<ClassLoader, TypePool.CacheProvider>makeMap())
+ *
+ * <p>Main differences:
+ *
+ * <ol>
+ *   <li>Control over the type of the cache. We many not want to use a java.util.ConcurrentMap
+ *   <li>Use our bootstrap proxy when matching against the bootstrap loader.
+ * </ol>
+ */
 public class DDCachingPoolStrategy implements PoolStrategy {
   private static final Map<ClassLoader, TypePool.CacheProvider> typePoolCache =
       Collections.synchronizedMap(new WeakHashMap<ClassLoader, TypePool.CacheProvider>());
 
   @Override
   public TypePool typePool(ClassFileLocator classFileLocator, ClassLoader classLoader) {
-    final ClassLoader key = null == classLoader ? Utils.getBootstrapProxy() : classLoader;
+    final ClassLoader key =
+        BOOTSTRAP_CLASSLOADER == classLoader ? Utils.getBootstrapProxy() : classLoader;
     TypePool.CacheProvider cache = typePoolCache.get(key);
     if (null == cache) {
       synchronized (key) {