Fix Channelz window reporting

Both Netty and OkHttp had local and remote windows flipped. Also, the
comment in OkHttp about "not tracked" wasn't true, so make it more
accurate and provide a _hint_ of what the window may be instead of just
-1.

netty/src/main/java/io/grpc/netty/Utils.java

@@ -466,8 +466,11 @@ class Utils {
     private final Http2FlowController remote;
 
     FlowControlReader(Http2Connection connection) {
-      local = connection.local().flowController();
+      // 'local' in Netty is the _controller_ that controls inbound data. 'local' in Channelz is
-      remote = connection.remote().flowController();
+      // the _present window_ provided by the remote that allows data to be sent. They are
+      // opposites.
+      local = connection.remote().flowController();
+      remote = connection.local().flowController();
       connectionStream = connection.connectionStream();
     }
 

netty/src/test/java/io/grpc/netty/NettyHandlerTestBase.java

@@ -456,8 +456,8 @@ public abstract class NettyHandlerTestBase<T extends Http2ConnectionHandler> {
   public void transportTracer_windowSizeDefault() throws Exception {
     manualSetUp();
     TransportStats transportStats = transportTracer.getStats();
-    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, transportStats.remoteFlowControlWindow);
+    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, transportStats.localFlowControlWindow);
-    assertEquals(flowControlWindow, transportStats.localFlowControlWindow);
+    assertEquals(flowControlWindow, transportStats.remoteFlowControlWindow);
   }
 
   @Test
@@ -465,31 +465,31 @@ public abstract class NettyHandlerTestBase<T extends Http2ConnectionHandler> {
     flowControlWindow = 1024 * 1024;
     manualSetUp();
     TransportStats transportStats = transportTracer.getStats();
-    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, transportStats.remoteFlowControlWindow);
+    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, transportStats.localFlowControlWindow);
-    assertEquals(flowControlWindow, transportStats.localFlowControlWindow);
+    assertEquals(flowControlWindow, transportStats.remoteFlowControlWindow);
   }
 
   @Test
   public void transportTracer_windowUpdate_remote() throws Exception {
     manualSetUp();
     TransportStats before = transportTracer.getStats();
-    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, before.remoteFlowControlWindow);
     assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, before.localFlowControlWindow);
+    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, before.remoteFlowControlWindow);
 
     ByteBuf serializedSettings = windowUpdate(0, 1000);
     channelRead(serializedSettings);
     TransportStats after = transportTracer.getStats();
     assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE + 1000,
-        after.remoteFlowControlWindow);
+        after.localFlowControlWindow);
-    assertEquals(flowControlWindow, after.localFlowControlWindow);
+    assertEquals(flowControlWindow, after.remoteFlowControlWindow);
   }
 
   @Test
   public void transportTracer_windowUpdate_local() throws Exception {
     manualSetUp();
     TransportStats before = transportTracer.getStats();
-    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, before.remoteFlowControlWindow);
+    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, before.localFlowControlWindow);
-    assertEquals(flowControlWindow, before.localFlowControlWindow);
+    assertEquals(flowControlWindow, before.remoteFlowControlWindow);
 
     // If the window size is below a certain threshold, netty will wait to apply the update.
     // Use a large increment to be sure that it exceeds the threshold.
@@ -497,7 +497,7 @@ public abstract class NettyHandlerTestBase<T extends Http2ConnectionHandler> {
         connection().connectionStream(), 8 * Http2CodecUtil.DEFAULT_WINDOW_SIZE);
 
     TransportStats after = transportTracer.getStats();
-    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, after.remoteFlowControlWindow);
+    assertEquals(Http2CodecUtil.DEFAULT_WINDOW_SIZE, after.localFlowControlWindow);
     assertEquals(flowControlWindow + 8 * Http2CodecUtil.DEFAULT_WINDOW_SIZE,
         connection().local().flowController().windowSize(connection().connectionStream()));
   }

okhttp/src/main/java/io/grpc/okhttp/OkHttpClientTransport.java

@@ -323,8 +323,10 @@ class OkHttpClientTransport implements ConnectionClientTransport, TransportExcep
         @Override
         public TransportTracer.FlowControlWindows read() {
           synchronized (lock) {
-            long local = -1; // okhttp does not track the local window size
+            long local = outboundFlow == null ? -1 : outboundFlow.windowUpdate(null, 0);
-            long remote = outboundFlow == null ? -1 : outboundFlow.windowUpdate(null, 0);
+            // connectionUnacknowledgedBytesRead is only readable by ClientFrameHandler, so we
+            // provide a lower bound.
+            long remote = (long) (initialWindowSize * DEFAULT_WINDOW_UPDATE_RATIO);
             return new TransportTracer.FlowControlWindows(local, remote);
           }
         }

okhttp/src/test/java/io/grpc/okhttp/OkHttpClientTransportTest.java

@@ -727,24 +727,21 @@ public class OkHttpClientTransportTest {
   public void transportTracer_windowSizeDefault() throws Exception {
     initTransport();
     TransportStats stats = getTransportStats(clientTransport);
-    assertEquals(INITIAL_WINDOW_SIZE, stats.remoteFlowControlWindow);
+    assertEquals(INITIAL_WINDOW_SIZE / 2, stats.remoteFlowControlWindow); // Lower bound
-    // okhttp does not track local window sizes
+    assertEquals(INITIAL_WINDOW_SIZE, stats.localFlowControlWindow);
-    assertEquals(-1, stats.localFlowControlWindow);
   }
 
   @Test
   public void transportTracer_windowSize_remote() throws Exception {
     initTransport();
     TransportStats before = getTransportStats(clientTransport);
-    assertEquals(INITIAL_WINDOW_SIZE, before.remoteFlowControlWindow);
+    assertEquals(INITIAL_WINDOW_SIZE / 2, before.remoteFlowControlWindow); // Lower bound
-    // okhttp does not track local window sizes
+    assertEquals(INITIAL_WINDOW_SIZE, before.localFlowControlWindow);
-    assertEquals(-1, before.localFlowControlWindow);
 
     frameHandler().windowUpdate(0, 1000);
     TransportStats after = getTransportStats(clientTransport);
-    assertEquals(INITIAL_WINDOW_SIZE + 1000, after.remoteFlowControlWindow);
+    assertEquals(INITIAL_WINDOW_SIZE / 2, after.remoteFlowControlWindow);
-    // okhttp does not track local window sizes
+    assertEquals(INITIAL_WINDOW_SIZE + 1000, after.localFlowControlWindow);
-    assertEquals(-1, after.localFlowControlWindow);
   }
 
   @Test