cronet: use reflection to load and invoke experimental APIs in ExperimentalBidirectionalStream.Builder (#6111)

* Use reflection to load and invoke setTrafficStats* and addRequestAnnotation methods for ExperimentalBidirectionalStream.Builder.

* Load reflection method lazily and cache for later usages.

cronet/src/main/java/io/grpc/cronet/CronetChannelBuilder.java

@@ -20,6 +20,7 @@ import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static io.grpc.internal.GrpcUtil.DEFAULT_MAX_MESSAGE_SIZE;
 
+import android.util.Log;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Preconditions;
 import com.google.common.util.concurrent.MoreExecutors;
@@ -31,6 +32,8 @@ import io.grpc.internal.ConnectionClientTransport;
 import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.SharedResourceHolder;
 import io.grpc.internal.TransportTracer;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.util.concurrent.Executor;
@@ -46,6 +49,8 @@ import org.chromium.net.ExperimentalCronetEngine;
 public final class CronetChannelBuilder extends
     AbstractManagedChannelImplBuilder<CronetChannelBuilder> {
 
+  private static final String LOG_TAG = "CronetChannelBuilder";
+
   /** BidirectionalStream.Builder factory used for getting the gRPC BidirectionalStream. */
   public static abstract class StreamBuilderFactory {
     public abstract BidirectionalStream.Builder newBidirectionalStreamBuilder(
@@ -245,6 +250,11 @@ public final class CronetChannelBuilder extends
    * StreamBuilderFactory impl that applies TrafficStats tags to stream builders that are produced.
    */
   private static class TaggingStreamFactory extends StreamBuilderFactory {
+    private static volatile boolean loadSetTrafficStatsTagAttempted;
+    private static volatile boolean loadSetTrafficStatsUidAttempted;
+    private static volatile Method setTrafficStatsTagMethod;
+    private static volatile Method setTrafficStatsUidMethod;
+
     private final CronetEngine cronetEngine;
     private final boolean trafficStatsTagSet;
     private final int trafficStatsTag;
@@ -271,12 +281,70 @@ public final class CronetChannelBuilder extends
           ((ExperimentalCronetEngine) cronetEngine)
               .newBidirectionalStreamBuilder(url, callback, executor);
       if (trafficStatsTagSet) {
-        builder.setTrafficStatsTag(trafficStatsTag);
+        setTrafficStatsTag(builder, trafficStatsTag);
       }
       if (trafficStatsUidSet) {
-        builder.setTrafficStatsUid(trafficStatsUid);
+        setTrafficStatsUid(builder, trafficStatsUid);
       }
       return builder;
     }
+
+    private static void setTrafficStatsTag(ExperimentalBidirectionalStream.Builder builder,
+        int tag) {
+      if (!loadSetTrafficStatsTagAttempted) {
+        synchronized (TaggingStreamFactory.class) {
+          if (!loadSetTrafficStatsTagAttempted) {
+            try {
+              setTrafficStatsTagMethod = ExperimentalBidirectionalStream.Builder.class
+                  .getMethod("setTrafficStatsTag", int.class);
+            } catch (NoSuchMethodException e) {
+              Log.w(LOG_TAG,
+                  "Failed to load method ExperimentalBidirectionalStream.Builder.setTrafficStatsTag",
+                  e);
+            } finally {
+              loadSetTrafficStatsTagAttempted = true;
+            }
+          }
+        }
+      }
+      if (setTrafficStatsTagMethod != null) {
+        try {
+          setTrafficStatsTagMethod.invoke(builder, tag);
+        } catch (InvocationTargetException e) {
+          throw new RuntimeException(e.getCause() == null ? e.getTargetException() : e.getCause());
+        } catch (IllegalAccessException e) {
+          Log.w(LOG_TAG, "Failed to set traffic stats tag: " + tag, e);
+        }
+      }
+    }
+
+    private static void setTrafficStatsUid(ExperimentalBidirectionalStream.Builder builder,
+        int uid) {
+      if (!loadSetTrafficStatsUidAttempted) {
+        synchronized (TaggingStreamFactory.class) {
+          if (!loadSetTrafficStatsUidAttempted) {
+            try {
+              setTrafficStatsUidMethod = ExperimentalBidirectionalStream.Builder.class
+                  .getMethod("setTrafficStatsUid", int.class);
+            } catch (NoSuchMethodException e) {
+              Log.w(LOG_TAG,
+                  "Failed to load method ExperimentalBidirectionalStream.Builder.setTrafficStatsUid",
+                  e);
+            } finally {
+              loadSetTrafficStatsUidAttempted = true;
+            }
+          }
+        }
+      }
+      if (setTrafficStatsUidMethod != null) {
+        try {
+          setTrafficStatsUidMethod.invoke(builder, uid);
+        } catch (InvocationTargetException e) {
+          throw new RuntimeException(e.getCause() == null ? e.getTargetException() : e.getCause());
+        } catch (IllegalAccessException e) {
+          Log.w(LOG_TAG, "Failed to set traffic stats uid: " + uid, e);
+        }
+      }
+    }
   }
 }

cronet/src/main/java/io/grpc/cronet/CronetClientStream.java

@@ -40,6 +40,8 @@ import io.grpc.internal.StatsTraceContext;
 import io.grpc.internal.TransportFrameUtil;
 import io.grpc.internal.TransportTracer;
 import io.grpc.internal.WritableBuffer;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
@@ -65,6 +67,9 @@ class CronetClientStream extends AbstractClientStream {
   private static final ByteBuffer EMPTY_BUFFER = ByteBuffer.allocateDirect(0);
   private static final String LOG_TAG = "grpc-java-cronet";
 
+  private static volatile boolean loadAddRequestAnnotationAttempted;
+  private static volatile Method addRequestAnnotationMethod;
+
   @Deprecated
   static final CallOptions.Key<Object> CRONET_ANNOTATION_KEY =
       CallOptions.Key.create("cronet-annotation");
@@ -182,12 +187,16 @@ class CronetClientStream extends AbstractClientStream {
       if (delayRequestHeader) {
         builder.delayRequestHeadersUntilFirstFlush(true);
       }
-      if (annotation != null) {
+      if (annotation != null || annotations != null) {
-        ((ExperimentalBidirectionalStream.Builder) builder).addRequestAnnotation(annotation);
+        ExperimentalBidirectionalStream.Builder expBidiStreamBuilder =
-      }
+            (ExperimentalBidirectionalStream.Builder) builder;
-      if (annotations != null) {
+        if (annotation != null) {
-        for (Object o : annotations) {
+          addRequestAnnotation(expBidiStreamBuilder, annotation);
-          ((ExperimentalBidirectionalStream.Builder) builder).addRequestAnnotation(o);
+        }
+        if (annotations != null) {
+          for (Object o : annotations) {
+            addRequestAnnotation(expBidiStreamBuilder, o);
+          }
         }
       }
       setGrpcHeaders(builder);
@@ -359,6 +368,35 @@ class CronetClientStream extends AbstractClientStream {
         && !TE_HEADER.name().equalsIgnoreCase(key);
   }
 
+  private static void addRequestAnnotation(ExperimentalBidirectionalStream.Builder builder,
+      Object annotation) {
+    if (!loadAddRequestAnnotationAttempted) {
+      synchronized (CronetClientStream.class) {
+        if (!loadAddRequestAnnotationAttempted) {
+          try {
+            addRequestAnnotationMethod = ExperimentalBidirectionalStream.Builder.class
+                .getMethod("addRequestAnnotation", Object.class);
+          } catch (NoSuchMethodException e) {
+            Log.w(LOG_TAG,
+                "Failed to load method ExperimentalBidirectionalStream.Builder.addRequestAnnotation",
+                e);
+          } finally {
+            loadAddRequestAnnotationAttempted = true;
+          }
+        }
+      }
+    }
+    if (addRequestAnnotationMethod != null) {
+      try {
+        addRequestAnnotationMethod.invoke(builder, annotation);
+      } catch (InvocationTargetException e) {
+        throw new RuntimeException(e.getCause() == null ? e.getTargetException() : e.getCause());
+      } catch (IllegalAccessException e) {
+        Log.w(LOG_TAG, "Failed to add request annotation: " + annotation, e);
+      }
+    }
+  }
+
   private void setGrpcHeaders(BidirectionalStream.Builder builder) {
     // Psuedo-headers are set by cronet.
     // All non-pseudo headers must come after pseudo headers.