Extract DDAgentResponseListener from DDApi.

Reduce references to DDApi

dd-trace-ot/src/main/java/datadog/opentracing/DDTracer.java

@@ -15,7 +15,7 @@ import datadog.trace.common.sampling.PrioritySampler;
 import datadog.trace.common.sampling.Sampler;
 import datadog.trace.common.writer.DDAgentWriter;
 import datadog.trace.common.writer.Writer;
-import datadog.trace.common.writer.ddagent.DDAgentApi;
+import datadog.trace.common.writer.ddagent.DDAgentResponseListener;
 import datadog.trace.context.ScopeListener;
 import io.opentracing.References;
 import io.opentracing.Scope;
@@ -245,11 +245,8 @@ public class DDTracer implements io.opentracing.Tracer, Closeable, datadog.trace
     injector = HttpCodec.createInjector(Config.get());
     extractor = HttpCodec.createExtractor(Config.get(), taggedHeaders);
 
-    if (this.writer instanceof DDAgentWriter) {
-      final DDAgentApi api = ((DDAgentWriter) this.writer).getApi();
-      if (sampler instanceof DDAgentApi.ResponseListener) {
-        api.addResponseListener((DDAgentApi.ResponseListener) this.sampler);
-      }
+    if (this.writer instanceof DDAgentWriter && sampler instanceof DDAgentResponseListener) {
+      ((DDAgentWriter) this.writer).addResponseListener((DDAgentResponseListener) this.sampler);
     }
 
     log.info("New instance: {}", this);

dd-trace-ot/src/main/java/datadog/trace/common/sampling/RateByServiceSampler.java

@@ -7,7 +7,7 @@ import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.node.NumericNode;
 import datadog.opentracing.DDSpan;
 import datadog.trace.api.sampling.PrioritySampling;
-import datadog.trace.common.writer.ddagent.DDAgentApi.ResponseListener;
+import datadog.trace.common.writer.ddagent.DDAgentResponseListener;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
@@ -19,7 +19,7 @@ import lombok.extern.slf4j.Slf4j;
  * <p>The configuration of (serviceName,env)->rate is configured by the core agent.
  */
 @Slf4j
-public class RateByServiceSampler implements Sampler, PrioritySampler, ResponseListener {
+public class RateByServiceSampler implements Sampler, PrioritySampler, DDAgentResponseListener {
   public static final String SAMPLING_AGENT_RATE = "_dd.agent_psr";
 
   /** Key for setting the default/baseline rate */

dd-trace-ot/src/main/java/datadog/trace/common/writer/DDAgentWriter.java

@@ -8,6 +8,7 @@ import static java.util.concurrent.TimeUnit.SECONDS;
 import datadog.opentracing.DDSpan;
 import datadog.trace.common.util.DaemonThreadFactory;
 import datadog.trace.common.writer.ddagent.DDAgentApi;
+import datadog.trace.common.writer.ddagent.DDAgentResponseListener;
 import datadog.trace.common.writer.ddagent.Monitor;
 import datadog.trace.common.writer.ddagent.TraceConsumer;
 import datadog.trace.common.writer.ddagent.TraceSerializingDisruptor;
@@ -110,6 +111,10 @@ public class DDAgentWriter implements Writer {
     apiPhaser.register(); // Register on behalf of the scheduled executor thread.
   }
 
+  public void addResponseListener(final DDAgentResponseListener listener) {
+    api.addResponseListener(listener);
+  }
+
   // Exposing some statistics for consumption by monitors
   public final long getDisruptorCapacity() {
     return disruptor.getDisruptorCapacity();

dd-trace-ot/src/main/java/datadog/trace/common/writer/ddagent/DDAgentApi.java

@@ -43,7 +43,7 @@ public class DDAgentApi {
   private static final String TRACES_ENDPOINT_V4 = "v0.4/traces";
   private static final long MILLISECONDS_BETWEEN_ERROR_LOG = TimeUnit.MINUTES.toMillis(5);
 
-  private final List<ResponseListener> responseListeners = new ArrayList<>();
+  private final List<DDAgentResponseListener> responseListeners = new ArrayList<>();
 
   private volatile long nextAllowedLogTime = 0;
 
@@ -76,7 +76,7 @@ public class DDAgentApi {
     }
   }
 
-  public void addResponseListener(final ResponseListener listener) {
+  public void addResponseListener(final DDAgentResponseListener listener) {
     if (!responseListeners.contains(listener)) {
       responseListeners.add(listener);
     }
@@ -186,7 +186,7 @@ public class DDAgentApi {
             final JsonNode parsedResponse = OBJECT_MAPPER.readTree(responseString);
             final String endpoint = tracesUrl.toString();
 
-            for (final ResponseListener listener : responseListeners) {
+            for (final DDAgentResponseListener listener : responseListeners) {
               listener.onResponse(endpoint, parsedResponse);
             }
             return Response.success(response.code(), parsedResponse);
@@ -364,9 +364,4 @@ public class DDAgentApi {
       return exception;
     }
   }
-
-  public interface ResponseListener {
-    /** Invoked after the api receives a response from the core agent. */
-    void onResponse(String endpoint, JsonNode responseJson);
-  }
 }

dd-trace-ot/src/main/java/datadog/trace/common/writer/ddagent/DDAgentResponseListener.java

@@ -0,0 +1,8 @@
+package datadog.trace.common.writer.ddagent;
+
+import com.fasterxml.jackson.databind.JsonNode;
+
+public interface DDAgentResponseListener {
+  /** Invoked after the api receives a response from the core agent. */
+  void onResponse(String endpoint, JsonNode responseJson);
+}

dd-trace-ot/src/test/groovy/datadog/trace/api/writer/DDAgentApiTest.groovy

@@ -4,7 +4,7 @@ import com.fasterxml.jackson.core.type.TypeReference
 import com.fasterxml.jackson.databind.JsonNode
 import datadog.opentracing.SpanFactory
 import datadog.trace.common.writer.ddagent.DDAgentApi
-import datadog.trace.common.writer.ddagent.DDAgentApi.ResponseListener
+import datadog.trace.common.writer.ddagent.DDAgentResponseListener
 import datadog.trace.util.test.DDSpecification
 
 import java.util.concurrent.atomic.AtomicLong
@@ -125,7 +125,7 @@ class DDAgentApiTest extends DDSpecification {
   def "Api ResponseListeners see 200 responses"() {
     setup:
     def agentResponse = new AtomicReference<String>(null)
-    ResponseListener responseListener = { String endpoint, JsonNode responseJson ->
+    DDAgentResponseListener responseListener = { String endpoint, JsonNode responseJson ->
       agentResponse.set(responseJson.toString())
     }
     def agent = httpServer {

dd-trace-ot/src/traceAgentTest/groovy/DDApiIntegrationTest.groovy

@@ -6,6 +6,7 @@ import datadog.opentracing.PendingTrace
 import datadog.trace.api.sampling.PrioritySampling
 import datadog.trace.common.writer.ListWriter
 import datadog.trace.common.writer.ddagent.DDAgentApi
+import datadog.trace.common.writer.ddagent.DDAgentResponseListener
 import datadog.trace.util.test.DDSpecification
 import org.testcontainers.containers.GenericContainer
 import org.testcontainers.containers.startupcheck.MinimumDurationRunningStartupCheckStrategy
@@ -64,7 +65,7 @@ class DDApiIntegrationTest {
     def endpoint = new AtomicReference<String>(null)
     def agentResponse = new AtomicReference<String>(null)
 
-    DDAgentApi.ResponseListener responseListener = { String receivedEndpoint, JsonNode responseJson ->
+    DDAgentResponseListener responseListener = { String receivedEndpoint, JsonNode responseJson ->
       endpoint.set(receivedEndpoint)
       agentResponse.set(responseJson.toString())
     }