core,services: Add ChannelTracing data object

Added `ChannelTrace` as an inner class of `Channelz`.

This is in preparation for the implementation of [Channel Tracing](https://github.com/grpc/proposal/blob/master/A3-channel-tracing.md)

3 files changed, 121 insertions, 14 deletions

diff --git a/services/src/main/java/io/grpc/services/ChannelzProtoUtil.java b/services/src/main/java/io/grpc/services/ChannelzProtoUtil.java
index 0403bf0b7..431a0ce9d 100644
--- a/services/src/main/java/io/grpc/services/ChannelzProtoUtil.java
+++ b/services/src/main/java/io/grpc/services/ChannelzProtoUtil.java
@@ -34,6 +34,9 @@ import io.grpc.channelz.v1.ChannelConnectivityState;
 import io.grpc.channelz.v1.ChannelConnectivityState.State;
 import io.grpc.channelz.v1.ChannelData;
 import io.grpc.channelz.v1.ChannelRef;
+import io.grpc.channelz.v1.ChannelTrace;
+import io.grpc.channelz.v1.ChannelTraceEvent;
+import io.grpc.channelz.v1.ChannelTraceEvent.Severity;
 import io.grpc.channelz.v1.GetServerSocketsResponse;
 import io.grpc.channelz.v1.GetServersResponse;
 import io.grpc.channelz.v1.GetTopChannelsResponse;
@@ -55,6 +58,7 @@ import io.grpc.channelz.v1.Subchannel;
 import io.grpc.channelz.v1.SubchannelRef;
 import io.grpc.internal.Channelz;
 import io.grpc.internal.Channelz.ChannelStats;
+import io.grpc.internal.Channelz.ChannelTrace.Event;
 import io.grpc.internal.Channelz.RootChannelList;
 import io.grpc.internal.Channelz.ServerList;
 import io.grpc.internal.Channelz.ServerSocketsList;
@@ -67,6 +71,7 @@ import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.security.cert.CertificateEncodingException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map.Entry;
 import java.util.concurrent.ExecutionException;
@@ -348,21 +353,49 @@ final class ChannelzProtoUtil {
   }
 
   static ChannelData extractChannelData(Channelz.ChannelStats stats) {
-    return ChannelData
-        .newBuilder()
-        .setTarget(stats.target)
+    ChannelData.Builder builder = ChannelData.newBuilder();
+    builder.setTarget(stats.target)
         .setState(toChannelConnectivityState(stats.state))
         .setCallsStarted(stats.callsStarted)
         .setCallsSucceeded(stats.callsSucceeded)
         .setCallsFailed(stats.callsFailed)
-        .setLastCallStartedTimestamp(Timestamps.fromMillis(stats.lastCallStartedMillis))
-        .build();
+        .setLastCallStartedTimestamp(Timestamps.fromMillis(stats.lastCallStartedMillis));
+    if (stats.channelTrace != null) {
+      builder.setTrace(toChannelTrace(stats.channelTrace));
+    }
+    return builder.build();
   }
 
   static ChannelConnectivityState toChannelConnectivityState(ConnectivityState s) {
     return ChannelConnectivityState.newBuilder().setState(toState(s)).build();
   }
 
+  private static ChannelTrace toChannelTrace(Channelz.ChannelTrace channelTrace) {
+    return ChannelTrace.newBuilder()
+        .setNumEventsLogged(channelTrace.numEventsLogged)
+        .setCreationTimestamp(Timestamps.fromNanos(channelTrace.creationTimeNanos))
+        .addAllEvents(toChannelTraceEvents(channelTrace.events))
+        .build();
+  }
+
+  private static List<ChannelTraceEvent> toChannelTraceEvents(List<Event> events) {
+    List<ChannelTraceEvent> channelTraceEvents = new ArrayList<ChannelTraceEvent>();
+    for (Event event : events) {
+      ChannelTraceEvent.Builder builder = ChannelTraceEvent.newBuilder()
+          .setDescription(event.description)
+          .setSeverity(Severity.valueOf(event.severity.name()))
+          .setTimestamp(Timestamps.fromNanos(event.timestampNanos));
+      if (event.channelRef != null) {
+        builder.setChannelRef(toChannelRef(event.channelRef));
+      }
+      if (event.subchannelRef != null) {
+        builder.setSubchannelRef(toSubchannelRef(event.subchannelRef));
+      }
+      channelTraceEvents.add(builder.build());
+    }
+    return Collections.unmodifiableList(channelTraceEvents);
+  }
+
   static State toState(ConnectivityState state) {
     if (state == null) {
       return State.UNKNOWN;
diff --git a/services/src/test/java/io/grpc/services/ChannelzProtoUtilTest.java b/services/src/test/java/io/grpc/services/ChannelzProtoUtilTest.java
index 407d8734b..8bdbb15f2 100644
--- a/services/src/test/java/io/grpc/services/ChannelzProtoUtilTest.java
+++ b/services/src/test/java/io/grpc/services/ChannelzProtoUtilTest.java
@@ -41,6 +41,8 @@ import io.grpc.channelz.v1.ChannelConnectivityState;
 import io.grpc.channelz.v1.ChannelConnectivityState.State;
 import io.grpc.channelz.v1.ChannelData;
 import io.grpc.channelz.v1.ChannelRef;
+import io.grpc.channelz.v1.ChannelTrace;
+import io.grpc.channelz.v1.ChannelTraceEvent;
 import io.grpc.channelz.v1.GetChannelRequest;
 import io.grpc.channelz.v1.GetServerSocketsResponse;
 import io.grpc.channelz.v1.GetServersResponse;
@@ -62,6 +64,8 @@ import io.grpc.channelz.v1.Subchannel;
 import io.grpc.channelz.v1.SubchannelRef;
 import io.grpc.internal.Channelz;
 import io.grpc.internal.Channelz.ChannelStats;
+import io.grpc.internal.Channelz.ChannelTrace.Event;
+import io.grpc.internal.Channelz.ChannelTrace.Event.Severity;
 import io.grpc.internal.Channelz.RootChannelList;
 import io.grpc.internal.Channelz.ServerList;
 import io.grpc.internal.Channelz.ServerSocketsList;
@@ -79,6 +83,7 @@ import java.net.Inet4Address;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.security.cert.Certificate;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Map.Entry;
 import org.junit.Test;
@@ -310,6 +315,12 @@ public final class ChannelzProtoUtilTest {
               .setPort(1000))
       .build();
 
+  private final ChannelTrace channelTrace = ChannelTrace
+      .newBuilder()
+      .setNumEventsLogged(1234)
+      .setCreationTimestamp(Timestamps.fromNanos(1000))
+      .build();
+
   @Test
   public void toChannelRef() {
     assertEquals(channelRef, ChannelzProtoUtil.toChannelRef(channel));
@@ -832,6 +843,68 @@ public final class ChannelzProtoUtilTest {
         .containsExactly(sockOptAdditional, otherOption);
   }
 
+  @Test
+  public void channelTrace_withoutEvents() {
+    ChannelStats stats = toBuilder(channel.stats)
+        .setChannelTrace(new Channelz.ChannelTrace.Builder()
+            .setNumEventsLogged(1234)
+            .setCreationTimeNanos(1000)
+            .build())
+        .build();
+
+    ChannelData protoStats = channelData.toBuilder().setTrace(channelTrace).build();
+    assertEquals(ChannelzProtoUtil.extractChannelData(stats), protoStats);
+  }
+
+  @Test
+  public void channelTrace_withEvents() {
+    Event event1 = new Event.Builder()
+        .setDescription("event1")
+        .setSeverity(Severity.CT_ERROR)
+        .setTimestampNaonos(12)
+        .setSubchannelRef(subchannel)
+        .build();
+    Event event2 = new Event.Builder()
+        .setDescription("event2")
+        .setTimestampNaonos(34)
+        .setSeverity(Severity.CT_INFO)
+        .setChannelRef(channel)
+        .build();
+
+    ChannelStats stats =
+        toBuilder(channel.stats)
+            .setChannelTrace(
+                new Channelz.ChannelTrace.Builder()
+                    .setNumEventsLogged(1234)
+                    .setCreationTimeNanos(1000)
+                    .setEvents(Arrays.asList(event1, event2))
+                    .build())
+            .build();
+
+    ChannelTraceEvent protoEvent1 = ChannelTraceEvent
+        .newBuilder()
+        .setDescription("event1")
+        .setTimestamp(Timestamps.fromNanos(12))
+        .setSeverity(ChannelTraceEvent.Severity.CT_ERROR)
+        .setSubchannelRef(subchannelRef)
+        .build();
+    ChannelTraceEvent protoEvent2 = ChannelTraceEvent
+        .newBuilder()
+        .setDescription("event2")
+        .setTimestamp(Timestamps.fromNanos(34))
+        .setSeverity(ChannelTraceEvent.Severity.CT_INFO)
+        .setChannelRef(channelRef)
+        .build();
+    ChannelData protoStats = channelData
+        .toBuilder()
+        .setTrace(channelTrace
+            .toBuilder()
+            .addAllEvents(Arrays.asList(protoEvent1, protoEvent2))
+            .build())
+        .build();
+    assertEquals(ChannelzProtoUtil.extractChannelData(stats), protoStats);
+  }
+
   private static ChannelStats.Builder toBuilder(ChannelStats stats) {
     ChannelStats.Builder builder = new ChannelStats.Builder()
         .setTarget(stats.target)
diff --git a/services/src/test/java/io/grpc/services/ChannelzTestHelper.java b/services/src/test/java/io/grpc/services/ChannelzTestHelper.java
index b326fa0bc..0acdd0287 100644
--- a/services/src/test/java/io/grpc/services/ChannelzTestHelper.java
+++ b/services/src/test/java/io/grpc/services/ChannelzTestHelper.java
@@ -148,15 +148,16 @@ final class ChannelzTestHelper {
   static final class TestChannel implements Instrumented<ChannelStats> {
     private final LogId id = LogId.allocate("channel-or-subchannel");
 
-    ChannelStats stats = new ChannelStats(
-      /*target=*/ "sometarget",
-      /*state=*/ ConnectivityState.READY,
-      /*callsStarted=*/ 1,
-      /*callsSucceeded=*/ 2,
-      /*callsFailed=*/ 3,
-      /*lastCallStartedMillis=*/ 4,
-      /*subchannels=*/ Collections.<WithLogId>emptyList(),
-      /*sockets=*/ Collections.<WithLogId>emptyList());
+    ChannelStats stats = new ChannelStats.Builder()
+        .setTarget("sometarget")
+        .setState(ConnectivityState.READY)
+        .setCallsStarted(1)
+        .setCallsSucceeded(2)
+        .setCallsFailed(3)
+        .setLastCallStartedMillis(4)
+        .setSubchannels(Collections.<WithLogId>emptyList())
+        .setSockets(Collections.<WithLogId>emptyList())
+        .build();
 
     @Override
     public ListenableFuture<ChannelStats> getStats() {