fix bugs with dubbo (open-telemetry#6640)

1. fix NullPointerException with dubbo getMetadata request

2. fix dubbo trace passing problem

the trace is third-demo -> consumer-demo -> provider-deme, but the
parent of provider-demo is third-demo.
wrong data like this
<img width="1994" alt="image"
src="https://user-images.githubusercontent.com/22729740/190597029-ea26569e-96b4-4e30-8ac3-46ead3871b92.png">

after fixed 
<img width="2015" alt="image"
src="https://user-images.githubusercontent.com/22729740/190596923-d65f8646-377d-47ab-9e65-6d75f1407ce0.png">

Co-authored-by: Mateusz Rzeszutek <mrzeszutek@splunk.com>

instrumentation/apache-dubbo-2.7/javaagent/src/test/groovy/io/opentelemetry/instrumentation/apachedubbo/v2_7/DubboTraceChainTest.groovy

@@ -0,0 +1,11 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.apachedubbo.v2_7
+
+import io.opentelemetry.instrumentation.test.AgentTestTrait
+
+class DubboTraceChainTest extends AbstractDubboTraceChainTest implements AgentTestTrait {
+}

instrumentation/apache-dubbo-2.7/library-autoconfigure/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/DubboHeadersSetter.java

@@ -13,5 +13,6 @@ enum DubboHeadersSetter implements TextMapSetter<DubboRequest> {
   @Override
   public void set(DubboRequest request, String key, String value) {
     request.context().setAttachment(key, value);
+    request.invocation().setAttachment(key, value);
   }
 }

instrumentation/apache-dubbo-2.7/library-autoconfigure/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/TracingFilter.java

@@ -35,6 +35,10 @@ public Result invoke(Invoker<?> invoker, Invocation invocation) {
     }
 
     RpcContext rpcContext = RpcContext.getContext();
+    if (rpcContext.getUrl() == null) {
+      return invoker.invoke(invocation);
+    }
+
     boolean isServer = rpcContext.isProviderSide();
     Instrumenter<DubboRequest, Result> instrumenter =
         isServer ? serverInstrumenter : clientInstrumenter;

instrumentation/apache-dubbo-2.7/library-autoconfigure/src/test/groovy/io/opentelemetry/instrumentation/apachedubbo/v2_7/DubboTraceChainTest.groovy

@@ -0,0 +1,11 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.apachedubbo.v2_7
+
+import io.opentelemetry.instrumentation.test.LibraryTestTrait
+
+class DubboTraceChainTest extends AbstractDubboTraceChainTest implements LibraryTestTrait {
+}

instrumentation/apache-dubbo-2.7/testing/src/main/groovy/io/opentelemetry/instrumentation/apachedubbo/v2_7/AbstractDubboTraceChainTest.groovy

@@ -0,0 +1,180 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.apachedubbo.v2_7
+
+import io.opentelemetry.api.trace.SpanKind
+import io.opentelemetry.instrumentation.apachedubbo.v2_7.api.HelloService
+import io.opentelemetry.instrumentation.apachedubbo.v2_7.api.MiddleService
+import io.opentelemetry.instrumentation.apachedubbo.v2_7.impl.HelloServiceImpl
+import io.opentelemetry.instrumentation.apachedubbo.v2_7.impl.MiddleServiceImpl
+import io.opentelemetry.instrumentation.test.InstrumentationSpecification
+import io.opentelemetry.instrumentation.test.utils.PortUtils
+import io.opentelemetry.semconv.trace.attributes.SemanticAttributes
+import org.apache.dubbo.common.utils.NetUtils
+import org.apache.dubbo.config.ApplicationConfig
+import org.apache.dubbo.config.ProtocolConfig
+import org.apache.dubbo.config.ReferenceConfig
+import org.apache.dubbo.config.RegistryConfig
+import org.apache.dubbo.config.ServiceConfig
+import org.apache.dubbo.config.bootstrap.DubboBootstrap
+import org.apache.dubbo.rpc.service.GenericService
+import spock.lang.Unroll
+
+import static io.opentelemetry.api.trace.SpanKind.CLIENT
+import static io.opentelemetry.api.trace.SpanKind.SERVER
+
+@Unroll
+abstract class AbstractDubboTraceChainTest extends InstrumentationSpecification {
+
+  def setupSpec() {
+    NetUtils.LOCAL_ADDRESS = InetAddress.getLoopbackAddress()
+  }
+
+  ReferenceConfig<HelloService> configureClient(int port) {
+    ReferenceConfig<HelloService> reference = new ReferenceConfig<>()
+    reference.setInterface(HelloService)
+    reference.setGeneric("true")
+    reference.setUrl("dubbo://localhost:" + port + "/?timeout=30000")
+    return reference
+  }
+
+  ReferenceConfig<HelloService> configureMiddleClient(int port) {
+    ReferenceConfig<MiddleService> reference = new ReferenceConfig<>()
+    reference.setInterface(MiddleService)
+    reference.setGeneric("true")
+    reference.setUrl("dubbo://localhost:" + port + "/?timeout=30000")
+    return reference
+  }
+
+  ServiceConfig configureServer() {
+    def registerConfig = new RegistryConfig()
+    registerConfig.setAddress("N/A")
+    ServiceConfig<HelloServiceImpl> service = new ServiceConfig<>()
+    service.setInterface(HelloService)
+    service.setRef(new HelloServiceImpl())
+    service.setRegistry(registerConfig)
+    return service
+  }
+
+  ServiceConfig configureMiddleServer(GenericService genericService) {
+    def registerConfig = new RegistryConfig()
+    registerConfig.setAddress("N/A")
+    ServiceConfig<MiddleServiceImpl> service = new ServiceConfig<>()
+    service.setInterface(MiddleService)
+    service.setRef(new MiddleServiceImpl(genericService))
+    service.setRegistry(registerConfig)
+    return service
+  }
+
+  def "test that context is propagated correctly in chained dubbo calls"() {
+    setup:
+    def port = PortUtils.findOpenPorts(2)
+    def middlePort = port + 1
+    def protocolConfig = new ProtocolConfig()
+    protocolConfig.setPort(port)
+
+    DubboBootstrap bootstrap = DubboBootstrap.newInstance()
+    bootstrap.application(new ApplicationConfig("dubbo-test-provider"))
+      .service(configureServer())
+      .protocol(protocolConfig)
+      .start()
+
+    def middleProtocolConfig = new ProtocolConfig()
+    middleProtocolConfig.setPort(middlePort)
+
+    def reference = configureClient(port)
+    DubboBootstrap middleBootstrap = DubboBootstrap.newInstance()
+    middleBootstrap.application(new ApplicationConfig("dubbo-demo-middle"))
+      .reference(reference)
+      .service(configureMiddleServer(reference.get()))
+      .protocol(middleProtocolConfig)
+      .start()
+
+
+    def consumerProtocolConfig = new ProtocolConfig()
+    consumerProtocolConfig.setRegister(false)
+
+    def middleReference = configureMiddleClient(middlePort)
+    DubboBootstrap consumerBootstrap = DubboBootstrap.newInstance()
+    consumerBootstrap.application(new ApplicationConfig("dubbo-demo-api-consumer"))
+      .reference(middleReference)
+      .protocol(consumerProtocolConfig)
+      .start()
+
+    when:
+    GenericService genericService = middleReference.get()
+    def response = runWithSpan("parent") {
+      genericService.$invoke("hello", [String.getName()] as String[], ["hello"] as Object[])
+    }
+
+    then:
+    response == "hello"
+    assertTraces(1) {
+      trace(0, 5) {
+        span(0) {
+          name "parent"
+          kind SpanKind.INTERNAL
+          hasNoParent()
+        }
+        span(1) {
+          name "org.apache.dubbo.rpc.service.GenericService/\$invoke"
+          kind CLIENT
+          childOf span(0)
+          attributes {
+            "$SemanticAttributes.RPC_SYSTEM" "apache_dubbo"
+            "$SemanticAttributes.RPC_SERVICE" "org.apache.dubbo.rpc.service.GenericService"
+            "$SemanticAttributes.RPC_METHOD" "\$invoke"
+            "$SemanticAttributes.NET_PEER_NAME" "localhost"
+            "$SemanticAttributes.NET_PEER_PORT" Long
+          }
+        }
+        span(2) {
+          name "io.opentelemetry.instrumentation.apachedubbo.v2_7.api.MiddleService/hello"
+          kind SERVER
+          childOf span(1)
+          attributes {
+            "$SemanticAttributes.RPC_SYSTEM" "apache_dubbo"
+            "$SemanticAttributes.RPC_SERVICE" "io.opentelemetry.instrumentation.apachedubbo.v2_7.api.MiddleService"
+            "$SemanticAttributes.RPC_METHOD" "hello"
+            "net.sock.peer.addr" String
+            "net.sock.peer.port" Long
+            "net.sock.family" { it == "inet6" || it == null }
+          }
+        }
+        span(3) {
+          name "org.apache.dubbo.rpc.service.GenericService/\$invoke"
+          kind CLIENT
+          childOf span(2)
+          attributes {
+            "$SemanticAttributes.RPC_SYSTEM" "apache_dubbo"
+            "$SemanticAttributes.RPC_SERVICE" "org.apache.dubbo.rpc.service.GenericService"
+            "$SemanticAttributes.RPC_METHOD" "\$invoke"
+            "$SemanticAttributes.NET_PEER_NAME" "localhost"
+            "$SemanticAttributes.NET_PEER_PORT" Long
+          }
+        }
+        span(4) {
+          name "io.opentelemetry.instrumentation.apachedubbo.v2_7.api.HelloService/hello"
+          kind SERVER
+          childOf span(3)
+          attributes {
+            "$SemanticAttributes.RPC_SYSTEM" "apache_dubbo"
+            "$SemanticAttributes.RPC_SERVICE" "io.opentelemetry.instrumentation.apachedubbo.v2_7.api.HelloService"
+            "$SemanticAttributes.RPC_METHOD" "hello"
+            "net.sock.peer.addr" String
+            "net.sock.peer.port" Long
+            "net.sock.family" { it == "inet6" || it == null }
+          }
+        }
+      }
+    }
+
+    cleanup:
+    bootstrap.destroy()
+    middleBootstrap.destroy()
+    consumerBootstrap.destroy()
+  }
+}

instrumentation/apache-dubbo-2.7/testing/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/api/MiddleService.java

@@ -0,0 +1,10 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.apachedubbo.v2_7.api;
+
+public interface MiddleService {
+  String hello(String hello);
+}

instrumentation/apache-dubbo-2.7/testing/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/impl/MiddleServiceImpl.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.apachedubbo.v2_7.impl;
+
+import io.opentelemetry.instrumentation.apachedubbo.v2_7.api.MiddleService;
+import org.apache.dubbo.rpc.service.GenericService;
+
+public class MiddleServiceImpl implements MiddleService {
+
+  private final GenericService genericService;
+
+  public MiddleServiceImpl(GenericService genericService) {
+    this.genericService = genericService;
+  }
+
+  @Override
+  public String hello(String hello) {
+    return genericService
+        .$invoke("hello", new String[] {String.class.getName()}, new Object[] {hello})
+        .toString();
+  }
+}