More fixes.

Notably added a transformer to make config easier to test with by making INSTANCE public static volatile.

dd-java-agent/instrumentation/akka-http-10.0/src/test/groovy/AkkaHttpClientInstrumentationTest.groovy

@@ -28,6 +28,7 @@ class AkkaHttpClientInstrumentationTest extends HttpClientTest<AkkaHttpClientDec
       .addHeaders(headers.collect { RawHeader.create(it.key, it.value) })
 
     def response = Http.get(system).singleRequest(request, materializer).toCompletableFuture().get()
+    blockUntilChildSpansFinished(1)
     callback?.call()
     return response.status().intValue()
   }

dd-java-agent/instrumentation/jax-rs-client/src/test/groovy/JaxRsClientAsyncTest.groovy

@@ -3,6 +3,7 @@ import datadog.trace.instrumentation.jaxrs.JaxRsClientDecorator
 import javax.ws.rs.client.AsyncInvoker
 import javax.ws.rs.client.Client
 import javax.ws.rs.client.ClientBuilder
+import javax.ws.rs.client.Entity
 import javax.ws.rs.client.WebTarget
 import javax.ws.rs.core.MediaType
 import javax.ws.rs.core.Response
@@ -19,8 +20,9 @@ abstract class JaxRsClientAsyncTest extends HttpClientTest<JaxRsClientDecorator>
     def builder = service.request(MediaType.TEXT_PLAIN)
     headers.each { builder.header(it.key, it.value) }
     AsyncInvoker request = builder.async()
-    
+
-    Response response = request.method(method).get()
+    def body = BODY_METHODS.contains(method) ? Entity.text("") : null
+    Response response = request.method(method, (Entity) body).get()
     callback?.call()
 
     return response.status

dd-java-agent/instrumentation/jax-rs-client/src/test/groovy/JaxRsClientTest.groovy

@@ -2,6 +2,7 @@ import datadog.trace.agent.test.base.HttpClientTest
 import datadog.trace.instrumentation.jaxrs.JaxRsClientDecorator
 import javax.ws.rs.client.Client
 import javax.ws.rs.client.ClientBuilder
+import javax.ws.rs.client.Entity
 import javax.ws.rs.client.Invocation
 import javax.ws.rs.client.WebTarget
 import javax.ws.rs.core.MediaType
@@ -19,7 +20,8 @@ abstract class JaxRsClientTest extends HttpClientTest<JaxRsClientDecorator> {
     WebTarget service = client.target(uri)
     Invocation.Builder request = service.request(MediaType.TEXT_PLAIN)
     headers.each { request.header(it.key, it.value) }
-    Response response = request.method(method)
+    def body = BODY_METHODS.contains(method) ? Entity.text("") : null
+    Response response = request.method(method, (Entity) body)
     callback?.call()
 
     return response.status

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

@@ -1,5 +1,8 @@
 package datadog.trace.agent.test;
 
+import static net.bytebuddy.matcher.ElementMatchers.named;
+import static net.bytebuddy.matcher.ElementMatchers.none;
+
 import ch.qos.logback.classic.Level;
 import ch.qos.logback.classic.Logger;
 import com.google.common.collect.Sets;
@@ -10,6 +13,7 @@ import datadog.trace.agent.test.asserts.ListWriterAssert;
 import datadog.trace.agent.test.utils.GlobalTracerUtils;
 import datadog.trace.agent.tooling.AgentInstaller;
 import datadog.trace.agent.tooling.Instrumenter;
+import datadog.trace.api.Config;
 import datadog.trace.api.GlobalTracer;
 import datadog.trace.common.writer.ListWriter;
 import datadog.trace.common.writer.Writer;
@@ -20,6 +24,8 @@ import groovy.transform.stc.SimpleType;
 import io.opentracing.Tracer;
 import java.lang.instrument.ClassFileTransformer;
 import java.lang.instrument.Instrumentation;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
 import java.util.List;
 import java.util.ServiceLoader;
 import java.util.Set;
@@ -28,8 +34,14 @@ import java.util.concurrent.atomic.AtomicInteger;
 import lombok.extern.slf4j.Slf4j;
 import net.bytebuddy.agent.ByteBuddyAgent;
 import net.bytebuddy.agent.builder.AgentBuilder;
+import net.bytebuddy.agent.builder.ResettableClassFileTransformer;
+import net.bytebuddy.description.modifier.FieldManifestation;
+import net.bytebuddy.description.modifier.Ownership;
+import net.bytebuddy.description.modifier.Visibility;
 import net.bytebuddy.description.type.TypeDescription;
+import net.bytebuddy.dynamic.ClassFileLocator;
 import net.bytebuddy.dynamic.DynamicType;
+import net.bytebuddy.dynamic.Transformer;
 import net.bytebuddy.utility.JavaModule;
 import org.junit.AfterClass;
 import org.junit.Before;
@@ -83,6 +95,12 @@ public abstract class AgentTestRunner extends Specification {
     ((Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME)).setLevel(Level.WARN);
     ((Logger) LoggerFactory.getLogger("datadog")).setLevel(Level.DEBUG);
 
+    try {
+      makeConfigInstanceModifiable();
+    } catch (final Exception e) {
+      throw new RuntimeException(e);
+    }
+
     TEST_WRITER =
         new ListWriter() {
           @Override
@@ -188,6 +206,44 @@ public abstract class AgentTestRunner extends Specification {
         : INSTRUMENTATION_ERROR_COUNT.get() + " Instrumentation errors during test";
   }
 
+  private static void makeConfigInstanceModifiable()
+      throws ClassNotFoundException, NoSuchFieldException {
+    final ResettableClassFileTransformer transformer =
+        new AgentBuilder.Default()
+            // Config is injected into the bootstrap, so we need to provide a locator.
+            .with(
+                new AgentBuilder.LocationStrategy.Simple(
+                    ClassFileLocator.ForClassLoader.ofSystemLoader()))
+            .ignore(none()) // Allow transforming boostrap classes
+            .type(named("datadog.trace.api.Config"))
+            .transform(
+                new AgentBuilder.Transformer() {
+                  @Override
+                  public DynamicType.Builder<?> transform(
+                      final DynamicType.Builder<?> builder,
+                      final TypeDescription typeDescription,
+                      final ClassLoader classLoader,
+                      final JavaModule module) {
+                    // Add transformer to modify INSTANCE field access.
+                    return builder
+                        .field(named("INSTANCE"))
+                        .transform(
+                            Transformer.ForField.withModifiers(
+                                Visibility.PUBLIC, Ownership.STATIC, FieldManifestation.VOLATILE));
+                  }
+                })
+            .installOn(INSTRUMENTATION);
+
+    final Field field = Config.class.getDeclaredField("INSTANCE");
+    assert Modifier.isPublic(field.getModifiers());
+    assert Modifier.isStatic(field.getModifiers());
+    assert Modifier.isVolatile(field.getModifiers());
+    assert !Modifier.isFinal(field.getModifiers());
+
+    // No longer needed (Unless class gets retransformed somehow).
+    INSTRUMENTATION.removeTransformer(transformer);
+  }
+
   public static void assertTraces(
       final int size,
       @ClosureParams(

dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/base/HttpClientTest.groovy

@@ -68,7 +68,7 @@ abstract class HttpClientTest<T extends HttpClientDecorator> extends AgentTestRu
   }
 
   @Unroll
-  def "basic #method request #url"() {
+  def "basic #method request #url - tagQueryString=#tagQueryString"() {
     when:
     def status = withConfigOverride(Config.HTTP_CLIENT_TAG_QUERY_STRING, "$tagQueryString") {
       doRequest(method, url)

dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/utils/TraceUtils.groovy

@@ -7,11 +7,12 @@ import io.opentracing.Scope
 import io.opentracing.util.GlobalTracer
 import lombok.SneakyThrows
 
-import java.lang.reflect.Field
 import java.lang.reflect.Modifier
 import java.util.concurrent.Callable
 
 class TraceUtils {
+  static final def CONFIG_INSTANCE_FIELD = Config.getDeclaredField("INSTANCE")
+
   private static final BaseDecorator DECORATOR = new BaseDecorator() {
     protected String[] instrumentationNames() {
       return new String[0]
@@ -61,14 +62,21 @@ class TraceUtils {
 
   @SneakyThrows
   synchronized static <T extends Object> Object withConfigOverride(final String name, final String value, final Callable<T> r) {
-    def existingConfig = Config.get()  // We can't reference INSTANCE directly or the reflection below will fail.
+    // Ensure the class was retransformed properly in AgentTestRunner.makeConfigInstanceModifiable()
+    assert Modifier.isPublic(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert Modifier.isStatic(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert Modifier.isVolatile(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert !Modifier.isFinal(CONFIG_INSTANCE_FIELD.getModifiers())
+
+    def existingConfig = Config.get()
     Properties properties = new Properties()
     properties.put(name, value)
-    setFinalStatic(Config.getDeclaredField("INSTANCE"), new Config(properties, existingConfig))
+    CONFIG_INSTANCE_FIELD.set(null, new Config(properties, existingConfig))
+    assert Config.get() != existingConfig
     try {
       return r.call()
     } finally {
-      setFinalStatic(Config.getDeclaredField("INSTANCE"), existingConfig)
+      CONFIG_INSTANCE_FIELD.set(null, existingConfig)
     }
   }
 
@@ -76,20 +84,12 @@ class TraceUtils {
    * Calling will reset the runtimeId too, so it might cause problems around runtimeId verification.
    */
   static void resetConfig() {
-    setFinalStatic(Config.getDeclaredField("INSTANCE"), new Config())
+    // Ensure the class was retransformed properly in AgentTestRunner.makeConfigInstanceModifiable()
-  }
+    assert Modifier.isPublic(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert Modifier.isStatic(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert Modifier.isVolatile(CONFIG_INSTANCE_FIELD.getModifiers())
+    assert !Modifier.isFinal(CONFIG_INSTANCE_FIELD.getModifiers())
 
-  private static void setFinalStatic(final Field field, final Object newValue) throws Exception {
+    CONFIG_INSTANCE_FIELD.set(null, new Config())
-    setFinal(field, null, newValue)
-  }
-
-  private static void setFinal(final Field field, final Object instance, final Object newValue) throws Exception {
-    field.setAccessible(true)
-
-    final Field modifiersField = Field.getDeclaredField("modifiers")
-    modifiersField.setAccessible(true)
-    modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL)
-
-    field.set(instance, newValue)
   }
 }