core: ManagedChannel should implement InternalInstrumented

core/src/main/java/io/grpc/ChannelStats.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2017, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A data class to represent a channel's stats.
+ */
+// Not final so that InternalChannelStats can make this class visible outside of io.grpc
+@Immutable
+class ChannelStats {
+  public final long callsStarted;
+  public final long callsSucceeded;
+  public final long callsFailed;
+  public final long lastCallStartedMillis;
+
+  ChannelStats(
+      long callsStarted, long callsSucceeded, long callsFailed, long lastCallStartedMillis) {
+    this.callsStarted = callsStarted;
+    this.callsSucceeded = callsSucceeded;
+    this.callsFailed = callsFailed;
+    this.lastCallStartedMillis = lastCallStartedMillis;
+  }
+}

core/src/main/java/io/grpc/InternalChannelStats.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2017, gRPC Authors All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc;
+
+/**
+ * An internal gRPC class. Do not use.
+ */
+@Internal
+public final class InternalChannelStats extends ChannelStats {
+  public InternalChannelStats(
+      long callsStarted,
+      long callsSucceeded,
+      long callsFailed,
+      long lastCallStartedMillis) {
+    super(callsStarted, callsSucceeded, callsFailed, lastCallStartedMillis);
+  }
+}

core/src/main/java/io/grpc/ManagedChannel.java

@@ -23,7 +23,8 @@ import javax.annotation.concurrent.ThreadSafe;
  * A {@link Channel} that provides lifecycle management.
  */
 @ThreadSafe
-public abstract class ManagedChannel extends Channel {
+public abstract class ManagedChannel
+    extends Channel implements InternalInstrumented<InternalChannelStats> {
   /**
    * Initiates an orderly shutdown in which preexisting calls continue but new calls are immediately
    * cancelled.

core/src/main/java/io/grpc/internal/AbstractManagedChannelImplBuilder.java

@@ -346,7 +346,7 @@ public abstract class AbstractManagedChannelImplBuilder
         GrpcUtil.STOPWATCH_SUPPLIER,
         getEffectiveInterceptors(),
         GrpcUtil.getProxyDetector(),
-        ChannelStats.getDefaultFactory());
+        ChannelTracer.getDefaultFactory());
   }
 
   @VisibleForTesting

core/src/main/java/io/grpc/internal/ChannelTracer.java

@@ -17,23 +17,19 @@
 package io.grpc.internal;
 
 import com.google.common.annotations.VisibleForTesting;
+import io.grpc.InternalChannelStats;
 
 /**
  * A collection of channel level stats for channelz.
  */
-final class ChannelStats {
+final class ChannelTracer {
   private final TimeProvider timeProvider;
   private final LongCounter callsStarted = LongCounterFactory.create();
   private final LongCounter callsSucceeded = LongCounterFactory.create();
   private final LongCounter callsFailed = LongCounterFactory.create();
   private volatile long lastCallStartedMillis;
 
-  private ChannelStats() {
+  ChannelTracer(TimeProvider timeProvider) {
-    timeProvider = SYSTEM_TIME_PROVIDER;
-  }
-
-  @VisibleForTesting
-  ChannelStats(TimeProvider timeProvider) {
     this.timeProvider = timeProvider;
   }
 
@@ -50,20 +46,9 @@ final class ChannelStats {
     }
   }
 
-  long getCallsStarted() {
+  public InternalChannelStats getStats() {
-    return callsStarted.value();
+    return new InternalChannelStats(
-  }
+        callsStarted.value(), callsSucceeded.value(), callsFailed.value(), lastCallStartedMillis);
-
-  long getCallsSucceeded() {
-    return callsSucceeded.value();
-  }
-
-  long getCallsFailed() {
-    return callsFailed.value();
-  }
-
-  long getLastCallStartedMillis() {
-    return lastCallStartedMillis;
   }
 
   @VisibleForTesting
@@ -72,24 +57,25 @@ final class ChannelStats {
     long currentTimeMillis();
   }
 
-  private static final TimeProvider SYSTEM_TIME_PROVIDER = new TimeProvider() {
+  public interface Factory {
+    ChannelTracer create();
+  }
+
+  static final TimeProvider SYSTEM_TIME_PROVIDER = new TimeProvider() {
     @Override
     public long currentTimeMillis() {
       return System.currentTimeMillis();
     }
   };
-  private static final Factory DEFAULT_FACTORY = new Factory() {
+
+  static final Factory DEFAULT_FACTORY = new Factory() {
     @Override
-    public ChannelStats create() {
+    public ChannelTracer create() {
-      return new ChannelStats(SYSTEM_TIME_PROVIDER);
+      return new ChannelTracer(SYSTEM_TIME_PROVIDER);
     }
   };
 
   public static Factory getDefaultFactory() {
     return DEFAULT_FACTORY;
   }
-
-  public interface Factory {
-    ChannelStats create();
-  }
 }

core/src/main/java/io/grpc/internal/ClientCallImpl.java

@@ -68,7 +68,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
 
   private final MethodDescriptor<ReqT, RespT> method;
   private final Executor callExecutor;
-  private final ChannelStats channelStats;
+  private final ChannelTracer channelTracer;
   private final Context context;
   private volatile ScheduledFuture<?> deadlineCancellationFuture;
   private final boolean unaryRequest;
@@ -88,7 +88,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
       MethodDescriptor<ReqT, RespT> method, Executor executor, CallOptions callOptions,
       ClientTransportProvider clientTransportProvider,
       ScheduledExecutorService deadlineCancellationExecutor,
-      ChannelStats channelStats) {
+      ChannelTracer channelTracer) {
     this.method = method;
     // If we know that the executor is a direct executor, we don't need to wrap it with a
     // SerializingExecutor. This is purely for performance reasons.
@@ -96,7 +96,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
     this.callExecutor = executor == directExecutor()
         ? new SerializeReentrantCallsDirectExecutor()
         : new SerializingExecutor(executor);
-    this.channelStats = channelStats;
+    this.channelTracer = channelTracer;
     // Propagate the context from the thread which initiated the call to all callbacks.
     this.context = Context.current();
     this.unaryRequest = method.getType() == MethodType.UNARY
@@ -261,7 +261,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
     stream.setCompressor(compressor);
     stream.setFullStreamDecompression(fullStreamDecompression);
     stream.setDecompressorRegistry(decompressorRegistry);
-    channelStats.reportCallStarted();
+    channelTracer.reportCallStarted();
     stream.start(new ClientStreamListenerImpl(observer));
 
     // Delay any sources of cancellation after start(), because most of the transports are broken if
@@ -557,7 +557,7 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT> {
         closeObserver(observer, status, trailers);
       } finally {
         removeContextListenerAndCancelDeadlineFuture();
-        channelStats.reportCallEnded(status.isOk());
+        channelTracer.reportCallEnded(status.isOk());
       }
     }
 

core/src/main/java/io/grpc/internal/ManagedChannelImpl.java

@@ -26,6 +26,8 @@ import static io.grpc.ConnectivityState.TRANSIENT_FAILURE;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Stopwatch;
 import com.google.common.base.Supplier;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
 import io.grpc.Attributes;
 import io.grpc.CallOptions;
 import io.grpc.Channel;
@@ -38,8 +40,8 @@ import io.grpc.ConnectivityStateInfo;
 import io.grpc.Context;
 import io.grpc.DecompressorRegistry;
 import io.grpc.EquivalentAddressGroup;
+import io.grpc.InternalChannelStats;
 import io.grpc.InternalLogId;
-import io.grpc.InternalWithLogId;
 import io.grpc.LoadBalancer;
 import io.grpc.LoadBalancer.PickResult;
 import io.grpc.LoadBalancer.PickSubchannelArgs;
@@ -76,7 +78,7 @@ import javax.annotation.concurrent.ThreadSafe;
 
 /** A communication channel for making outgoing RPCs. */
 @ThreadSafe
-public final class ManagedChannelImpl extends ManagedChannel implements InternalWithLogId {
+public final class ManagedChannelImpl extends ManagedChannel {
   static final Logger logger = Logger.getLogger(ManagedChannelImpl.class.getName());
 
   // Matching this pattern means the target string is a URI target or at least intended to be one.
@@ -188,8 +190,8 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
 
   private final ManagedChannelReference phantom;
 
-  private final ChannelStats.Factory channelStatsFactory; // to create new stats for each oobchannel
+  private final ChannelTracer.Factory channelTracerFactory; // new tracer for each oobchannel
-  final ChannelStats channelStats;
+  private final ChannelTracer channelTracer;
 
   // Called from channelExecutor
   private final ManagedClientTransport.Listener delayedTransportListener =
@@ -260,6 +262,13 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
         }
       };
 
+  @Override
+  public ListenableFuture<InternalChannelStats> getStats() {
+    SettableFuture<InternalChannelStats> ret = SettableFuture.create();
+    ret.set(channelTracer.getStats());
+    return ret;
+  }
+
   // Run from channelExecutor
   private class IdleModeTimer implements Runnable {
     // Only mutated from channelExecutor
@@ -434,7 +443,7 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
       Supplier<Stopwatch> stopwatchSupplier,
       List<ClientInterceptor> interceptors,
       ProxyDetector proxyDetector,
-      ChannelStats.Factory channelStatsFactory) {
+      ChannelTracer.Factory channelTracerFactory) {
     this.target = checkNotNull(builder.target, "target");
     this.nameResolverFactory = builder.getNameResolverFactory();
     this.nameResolverParams = checkNotNull(builder.getNameResolverParams(), "nameResolverParams");
@@ -467,8 +476,8 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
     this.proxyDetector = proxyDetector;
 
     phantom = new ManagedChannelReference(this);
-    this.channelStatsFactory = channelStatsFactory;
+    this.channelTracerFactory = channelTracerFactory;
-    channelStats = channelStatsFactory.create();
+    channelTracer = channelTracerFactory.create();
     logger.log(Level.FINE, "[{0}] Created with target {1}", new Object[] {getLogId(), target});
   }
 
@@ -620,7 +629,7 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
               callOptions,
               transportProvider,
               terminated ? null : transportFactory.getScheduledExecutorService(),
-              channelStats)
+          channelTracer)
           .setFullStreamDecompression(fullStreamDecompression)
           .setDecompressorRegistry(decompressorRegistry)
           .setCompressorRegistry(compressorRegistry);
@@ -817,7 +826,7 @@ public final class ManagedChannelImpl extends ManagedChannel implements Internal
       checkState(!terminated, "Channel is terminated");
       final OobChannel oobChannel = new OobChannel(
           authority, oobExecutorPool, transportFactory.getScheduledExecutorService(),
-          channelExecutor, channelStatsFactory.create());
+          channelExecutor, channelTracerFactory.create());
       final InternalSubchannel internalSubchannel = new InternalSubchannel(
           addressGroup, authority, userAgent, backoffPolicyProvider, transportFactory,
           transportFactory.getScheduledExecutorService(), stopwatchSupplier, channelExecutor,

core/src/main/java/io/grpc/internal/OobChannel.java

@@ -19,12 +19,15 @@ package io.grpc.internal;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
 import io.grpc.Attributes;
 import io.grpc.CallOptions;
 import io.grpc.ClientCall;
 import io.grpc.ConnectivityStateInfo;
 import io.grpc.Context;
 import io.grpc.EquivalentAddressGroup;
+import io.grpc.InternalChannelStats;
 import io.grpc.InternalLogId;
 import io.grpc.InternalWithLogId;
 import io.grpc.LoadBalancer.Subchannel;
@@ -65,7 +68,7 @@ final class OobChannel extends ManagedChannel implements InternalWithLogId {
   private final ScheduledExecutorService deadlineCancellationExecutor;
   private final CountDownLatch terminatedLatch = new CountDownLatch(1);
   private volatile boolean shutdown;
-  final ChannelStats channelStats;
+  private final ChannelTracer channelTracer;
 
   private final ClientTransportProvider transportProvider = new ClientTransportProvider() {
     @Override
@@ -86,7 +89,7 @@ final class OobChannel extends ManagedChannel implements InternalWithLogId {
   OobChannel(
       String authority, ObjectPool<? extends Executor> executorPool,
       ScheduledExecutorService deadlineCancellationExecutor, ChannelExecutor channelExecutor,
-      ChannelStats channelStats) {
+      ChannelTracer channelTracer) {
     this.authority = checkNotNull(authority, "authority");
     this.executorPool = checkNotNull(executorPool, "executorPool");
     this.executor = checkNotNull(executorPool.getObject(), "executor");
@@ -114,7 +117,7 @@ final class OobChannel extends ManagedChannel implements InternalWithLogId {
           // Don't care
         }
       });
-    this.channelStats = channelStats;
+    this.channelTracer = channelTracer;
   }
 
   // Must be called only once, right after the OobChannel is created.
@@ -168,7 +171,7 @@ final class OobChannel extends ManagedChannel implements InternalWithLogId {
       MethodDescriptor<RequestT, ResponseT> methodDescriptor, CallOptions callOptions) {
     return new ClientCallImpl<RequestT, ResponseT>(methodDescriptor,
         callOptions.getExecutor() == null ? executor : callOptions.getExecutor(),
-        callOptions, transportProvider, deadlineCancellationExecutor, channelStats);
+        callOptions, transportProvider, deadlineCancellationExecutor, channelTracer);
   }
 
   @Override
@@ -243,4 +246,11 @@ final class OobChannel extends ManagedChannel implements InternalWithLogId {
   Subchannel getSubchannel() {
     return subchannelImpl;
   }
+
+  @Override
+  public ListenableFuture<InternalChannelStats> getStats() {
+    SettableFuture<InternalChannelStats> ret = SettableFuture.create();
+    ret.set(channelTracer.getStats());
+    return ret;
+  }
 }

core/src/test/java/io/grpc/internal/ClientCallImplTest.java

@@ -89,7 +89,7 @@ public class ClientCallImplTest {
   private final FakeClock fakeClock = new FakeClock();
   private final ScheduledExecutorService deadlineCancellationExecutor =
       fakeClock.getScheduledExecutorService();
-  private final ChannelStats channaleStats = ChannelStats.getDefaultFactory().create();
+  private final ChannelTracer channelTracer = ChannelTracer.getDefaultFactory().create();
   private final DecompressorRegistry decompressorRegistry =
       DecompressorRegistry.getDefaultInstance().with(new Codec.Gzip(), true);
   private final MethodDescriptor<Void, Void> method = MethodDescriptor.<Void, Void>newBuilder()
@@ -151,7 +151,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     call.start(callListener, new Metadata());
     verify(stream).start(listenerArgumentCaptor.capture());
     final ClientStreamListener streamListener = listenerArgumentCaptor.getValue();
@@ -172,7 +172,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     call.start(callListener, new Metadata());
     verify(stream).start(listenerArgumentCaptor.capture());
     final ClientStreamListener streamListener = listenerArgumentCaptor.getValue();
@@ -208,7 +208,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     call.start(callListener, new Metadata());
     verify(stream).start(listenerArgumentCaptor.capture());
     final ClientStreamListener streamListener = listenerArgumentCaptor.getValue();
@@ -242,7 +242,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     call.start(callListener, new Metadata());
     verify(stream).start(listenerArgumentCaptor.capture());
     final ClientStreamListener streamListener = listenerArgumentCaptor.getValue();
@@ -275,7 +275,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     call.start(callListener, new Metadata());
@@ -298,7 +298,7 @@ public class ClientCallImplTest {
         baseCallOptions.withAuthority("overridden-authority"),
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     call.start(callListener, new Metadata());
@@ -314,7 +314,7 @@ public class ClientCallImplTest {
         callOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
         .setDecompressorRegistry(decompressorRegistry);
     final Metadata metadata = new Metadata();
 
@@ -332,7 +332,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     call.start(callListener, new Metadata());
@@ -501,7 +501,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     Context.ROOT.attach();
@@ -575,7 +575,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     previous.attach();
@@ -604,7 +604,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
         .setDecompressorRegistry(decompressorRegistry);
 
     previous.attach();
@@ -648,7 +648,7 @@ public class ClientCallImplTest {
         callOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
     call.start(callListener, new Metadata());
     verify(transport, times(0))
@@ -671,7 +671,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     Metadata headers = new Metadata();
 
@@ -699,7 +699,7 @@ public class ClientCallImplTest {
         callOpts,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     Metadata headers = new Metadata();
 
@@ -727,7 +727,7 @@ public class ClientCallImplTest {
         callOpts,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     Metadata headers = new Metadata();
 
@@ -753,7 +753,7 @@ public class ClientCallImplTest {
         baseCallOptions.withDeadline(Deadline.after(1, TimeUnit.SECONDS)),
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     call.start(callListener, new Metadata());
 
@@ -777,7 +777,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     call.start(callListener, new Metadata());
 
@@ -797,7 +797,7 @@ public class ClientCallImplTest {
         baseCallOptions.withDeadline(Deadline.after(1, TimeUnit.SECONDS)),
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     call.start(callListener, new Metadata());
     call.cancel("canceled", null);
 
@@ -821,7 +821,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
 
     Metadata headers = new Metadata();
 
@@ -838,7 +838,7 @@ public class ClientCallImplTest {
         baseCallOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats);
+        channelTracer);
     final Exception cause = new Exception();
     ClientCall.Listener<Void> callListener =
         new ClientCall.Listener<Void>() {
@@ -875,7 +875,7 @@ public class ClientCallImplTest {
         callOptions,
         provider,
         deadlineCancellationExecutor,
-        channaleStats)
+        channelTracer)
             .setDecompressorRegistry(decompressorRegistry);
 
     call.start(callListener, new Metadata());
@@ -888,7 +888,7 @@ public class ClientCallImplTest {
   public void getAttributes() {
     ClientCallImpl<Void, Void> call = new ClientCallImpl<Void, Void>(
         method, MoreExecutors.directExecutor(), baseCallOptions, provider,
-        deadlineCancellationExecutor, channaleStats);
+        deadlineCancellationExecutor, channelTracer);
     Attributes attrs =
         Attributes.newBuilder().set(Key.<String>of("fake key"), "fake value").build();
     when(stream.getAttributes()).thenReturn(attrs);

core/src/test/java/io/grpc/internal/ManagedChannelImplIdlenessTest.java

@@ -143,7 +143,7 @@ public class ManagedChannelImplIdlenessTest {
         builder, mockTransportFactory, new FakeBackoffPolicyProvider(),
         oobExecutorPool, timer.getStopwatchSupplier(),
         Collections.<ClientInterceptor>emptyList(),
-        GrpcUtil.NOOP_PROXY_DETECTOR, ChannelStats.getDefaultFactory());
+        GrpcUtil.NOOP_PROXY_DETECTOR, ChannelTracer.getDefaultFactory());
     newTransports = TestUtils.captureTransports(mockTransportFactory);
 
     for (int i = 0; i < 2; i++) {

core/src/test/java/io/grpc/internal/ManagedChannelImplTest.java

@@ -60,6 +60,8 @@ import io.grpc.ConnectivityStateInfo;
 import io.grpc.Context;
 import io.grpc.EquivalentAddressGroup;
 import io.grpc.IntegerMarshaller;
+import io.grpc.InternalChannelStats;
+import io.grpc.InternalInstrumented;
 import io.grpc.InternalLogId;
 import io.grpc.LoadBalancer;
 import io.grpc.LoadBalancer.Helper;
@@ -138,15 +140,15 @@ public class ManagedChannelImplTest {
   private final FakeClock timer = new FakeClock();
   private final FakeClock executor = new FakeClock();
   private final FakeClock oobExecutor = new FakeClock();
-  private final ChannelStats.Factory channelStatsFactory = new ChannelStats.Factory() {
+  private final ChannelTracer.Factory channelStatsFactory = new ChannelTracer.Factory() {
     @Override
-    public ChannelStats create() {
+    public ChannelTracer create() {
-      return new ChannelStats(new ChannelStats.TimeProvider() {
+      return new ChannelTracer(new ChannelTracer.TimeProvider() {
-          @Override
+        @Override
-          public long currentTimeMillis() {
+        public long currentTimeMillis() {
-            return executor.currentTimeMillis();
+          return executor.currentTimeMillis();
-          }
+        }
-        });
+      });
     }
   };
 
@@ -1662,10 +1664,10 @@ public class ManagedChannelImplTest {
   public void channelStat_callStarted() throws Exception {
     createChannel(new FakeNameResolverFactory(true), NO_INTERCEPTOR);
     ClientCall<String, Integer> call = channel.newCall(method, CallOptions.DEFAULT);
-    assertEquals(0, channel.channelStats.getCallsStarted());
+    assertEquals(0, getStats(channel).callsStarted);
     call.start(mockCallListener, new Metadata());
-    assertEquals(1, channel.channelStats.getCallsStarted());
+    assertEquals(1, getStats(channel).callsStarted);
-    assertEquals(executor.currentTimeMillis(), channel.channelStats.getLastCallStartedMillis());
+    assertEquals(executor.currentTimeMillis(), getStats(channel).lastCallStartedMillis);
   }
 
   @Test
@@ -1701,12 +1703,12 @@ public class ManagedChannelImplTest {
     // the actual test
     ClientStreamListener streamListener = streamListenerCaptor.getValue();
     call.halfClose();
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
     streamListener.closed(Status.OK, new Metadata());
     executor.runDueTasks();
-    assertEquals(1, channel.channelStats.getCallsSucceeded());
+    assertEquals(1, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
   }
 
   @Test
@@ -1716,12 +1718,12 @@ public class ManagedChannelImplTest {
     call.start(mockCallListener, new Metadata());
     call.cancel("msg", null);
 
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
     executor.runDueTasks();
     verify(mockCallListener).onClose(any(Status.class), any(Metadata.class));
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(1, channel.channelStats.getCallsFailed());
+    assertEquals(1, getStats(channel).callsFailed);
   }
 
   @Test
@@ -1730,12 +1732,12 @@ public class ManagedChannelImplTest {
     OobChannel oob1 = (OobChannel) helper.createOobChannel(addressGroup, "oob1authority");
     ClientCall<String, Integer> call = oob1.newCall(method, CallOptions.DEFAULT);
 
-    assertEquals(0, channel.channelStats.getCallsStarted());
+    assertEquals(0, getStats(channel).callsStarted);
     call.start(mockCallListener, new Metadata());
     // only oob channel stats updated
-    assertEquals(1, oob1.channelStats.getCallsStarted());
+    assertEquals(1, getStats(oob1).callsStarted);
-    assertEquals(0, channel.channelStats.getCallsStarted());
+    assertEquals(0, getStats(channel).callsStarted);
-    assertEquals(executor.currentTimeMillis(), oob1.channelStats.getLastCallStartedMillis());
+    assertEquals(executor.currentTimeMillis(), getStats(oob1).lastCallStartedMillis);
   }
 
   @Test
@@ -1765,15 +1767,15 @@ public class ManagedChannelImplTest {
     // the actual test
     ClientStreamListener streamListener = streamListenerCaptor.getValue();
     call.halfClose();
-    assertEquals(0, oobChannel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(oobChannel).callsSucceeded);
-    assertEquals(0, oobChannel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(oobChannel).callsFailed);
     streamListener.closed(Status.OK, new Metadata());
     callExecutor.runDueTasks();
     // only oob channel stats updated
-    assertEquals(1, oobChannel.channelStats.getCallsSucceeded());
+    assertEquals(1, getStats(oobChannel).callsSucceeded);
-    assertEquals(0, oobChannel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(oobChannel).callsFailed);
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
   }
 
   @Test
@@ -1784,15 +1786,15 @@ public class ManagedChannelImplTest {
     call.start(mockCallListener, new Metadata());
     call.cancel("msg", null);
 
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
     oobExecutor.runDueTasks();
     // only oob channel stats updated
     verify(mockCallListener).onClose(any(Status.class), any(Metadata.class));
-    assertEquals(0, oob1.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(oob1).callsSucceeded);
-    assertEquals(1, oob1.channelStats.getCallsFailed());
+    assertEquals(1, getStats(oob1).callsFailed);
-    assertEquals(0, channel.channelStats.getCallsSucceeded());
+    assertEquals(0, getStats(channel).callsSucceeded);
-    assertEquals(0, channel.channelStats.getCallsFailed());
+    assertEquals(0, getStats(channel).callsFailed);
   }
 
   private static class FakeBackoffPolicyProvider implements BackoffPolicy.Provider {
@@ -1907,4 +1909,9 @@ public class ManagedChannelImplTest {
       return "fake";
     }
   }
+
+  private static InternalChannelStats getStats(
+      InternalInstrumented<InternalChannelStats> instrumented) throws Exception {
+    return instrumented.getStats().get();
+  }
 }