benchmarks: Avoid implementing Future

It's a lot of code and there are classes in Guava are better. This was noticed
with a lint checker. This commit does change the error-handling behavior, as
previous the code wrongly cancelled the Future instead of setting it to have an
exception.

benchmarks/src/main/java/io/grpc/benchmarks/qps/AsyncClient.java

@@ -34,11 +34,10 @@ import static io.grpc.benchmarks.qps.ClientConfiguration.ClientParam.TLS;
 import static io.grpc.benchmarks.qps.ClientConfiguration.ClientParam.TRANSPORT;
 import static io.grpc.benchmarks.qps.ClientConfiguration.ClientParam.WARMUP_DURATION;
 
-import com.google.common.base.Preconditions;
+import com.google.common.util.concurrent.SettableFuture;
 import com.google.protobuf.ByteString;
 import io.grpc.Channel;
 import io.grpc.ManagedChannel;
-import io.grpc.Status;
 import io.grpc.benchmarks.proto.BenchmarkServiceGrpc;
 import io.grpc.benchmarks.proto.BenchmarkServiceGrpc.BenchmarkServiceStub;
 import io.grpc.benchmarks.proto.Messages.Payload;
@@ -47,7 +46,6 @@ import io.grpc.benchmarks.proto.Messages.SimpleResponse;
 import io.grpc.stub.StreamObserver;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.CancellationException;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
 import org.HdrHistogram.Histogram;
@@ -152,7 +150,7 @@ public class AsyncClient {
                                          final long endTime) {
     final BenchmarkServiceStub stub = BenchmarkServiceGrpc.newStub(channel);
     final Histogram histogram = new Histogram(HISTOGRAM_MAX_VALUE, HISTOGRAM_PRECISION);
-    final HistogramFuture future = new HistogramFuture(histogram);
+    final SettableFuture<Histogram> future = SettableFuture.create();
 
     stub.unaryCall(request, new StreamObserver<SimpleResponse>() {
       long lastCall = System.nanoTime();
@@ -163,11 +161,7 @@ public class AsyncClient {
 
       @Override
       public void onError(Throwable t) {
-        Status status = Status.fromThrowable(t);
-        System.err.println("Encountered an error in unaryCall. Status is " + status);
-        t.printStackTrace();
-
-        future.cancel(true);
+        future.setException(new RuntimeException("Encountered an error in unaryCall", t));
       }
 
       @Override
@@ -180,7 +174,7 @@ public class AsyncClient {
         if (endTime - now > 0) {
           stub.unaryCall(request, this);
         } else {
-          future.done();
+          future.set(histogram);
         }
       }
     });
@@ -192,7 +186,7 @@ public class AsyncClient {
                                              final long endTime) {
     final BenchmarkServiceStub stub = BenchmarkServiceGrpc.newStub(channel);
     final Histogram histogram = new Histogram(HISTOGRAM_MAX_VALUE, HISTOGRAM_PRECISION);
-    final HistogramFuture future = new HistogramFuture(histogram);
+    final SettableFuture<Histogram> future = SettableFuture.create();
 
     ThisIsAHackStreamObserver responseObserver =
         new ThisIsAHackStreamObserver(request, histogram, future, endTime);
@@ -211,7 +205,7 @@ public class AsyncClient {
 
     final SimpleRequest request;
     final Histogram histogram;
-    final HistogramFuture future;
+    final SettableFuture<Histogram> future;
     final long endTime;
     long lastCall = System.nanoTime();
 
@@ -219,7 +213,7 @@ public class AsyncClient {
 
     ThisIsAHackStreamObserver(SimpleRequest request,
                               Histogram histogram,
-                              HistogramFuture future,
+                              SettableFuture<Histogram> future,
                               long endTime) {
       this.request = request;
       this.histogram = histogram;
@@ -243,16 +237,12 @@ public class AsyncClient {
 
     @Override
     public void onError(Throwable t) {
-      Status status = Status.fromThrowable(t);
-      System.err.println("Encountered an error in streamingCall. Status is " + status);
-      t.printStackTrace();
-
-      future.cancel(true);
+      future.setException(new RuntimeException("Encountered an error in streamingCall", t));
     }
 
     @Override
     public void onCompleted() {
-      future.done();
+      future.set(histogram);
     }
   }
 
@@ -318,58 +308,4 @@ public class AsyncClient {
     AsyncClient client = new AsyncClient(config);
     client.run();
   }
-
-  private static class HistogramFuture implements Future<Histogram> {
-    private final Histogram histogram;
-    private boolean canceled;
-    private boolean done;
-
-    HistogramFuture(Histogram histogram) {
-      Preconditions.checkNotNull(histogram, "histogram");
-      this.histogram = histogram;
-    }
-
-    @Override
-    public synchronized boolean cancel(boolean mayInterruptIfRunning) {
-      if (!done && !canceled) {
-        canceled = true;
-        notifyAll();
-        return true;
-      }
-      return false;
-    }
-
-    @Override
-    public synchronized boolean isCancelled() {
-      return canceled;
-    }
-
-    @Override
-    public synchronized boolean isDone() {
-      return done || canceled;
-    }
-
-    @Override
-    public synchronized Histogram get() throws InterruptedException {
-      while (!isDone() && !isCancelled()) {
-        wait();
-      }
-
-      if (isCancelled()) {
-        throw new CancellationException();
-      }
-
-      return histogram;
-    }
-
-    @Override
-    public Histogram get(long timeout, TimeUnit unit) {
-      throw new UnsupportedOperationException();
-    }
-
-    private synchronized void done() {
-      done = true;
-      notifyAll();
-    }
-  }
 }