chore: capture sub-ms latency measurements (#9789)

Author: igorbernstein2

bigtable/bigtable-proxy/src/main/java/com/google/cloud/bigtable/examples/proxy/metrics/MetricsImpl.java

@@ -292,12 +292,12 @@ public void recordCallStarted(MetricsAttributes attrs) {
   public void recordCredLatency(MetricsAttributes attrs, Status status, Duration duration) {
     Attributes attributes =
         unwrap(attrs).toBuilder().put(STATUS_KEY, status.getCode().name()).build();
-    clientCredLatencies.record(duration.toMillis(), attributes);
+    clientCredLatencies.record(toMs(duration), attributes);
   }
 
   @Override
   public void recordQueueLatency(MetricsAttributes attrs, Duration duration) {
-    clientQueueLatencies.record(duration.toMillis(), unwrap(attrs));
+    clientQueueLatencies.record(toMs(duration), unwrap(attrs));
   }
 
   @Override
@@ -312,7 +312,7 @@ public void recordResponseSize(MetricsAttributes attrs, long size) {
 
   @Override
   public void recordGfeLatency(MetricsAttributes attrs, Duration duration) {
-    gfeLatency.record(duration.toMillis(), unwrap(attrs));
+    gfeLatency.record(toMs(duration), unwrap(attrs));
   }
 
   @Override
@@ -325,13 +325,13 @@ public void recordCallLatency(MetricsAttributes attrs, Status status, Duration d
     Attributes attributes =
         unwrap(attrs).toBuilder().put(STATUS_KEY, status.getCode().name()).build();
 
-    clientCallLatencies.record(duration.toMillis(), attributes);
+    clientCallLatencies.record(toMs(duration), attributes);
     numOutstandingRpcs.decrementAndGet();
   }
 
   @Override
   public void recordFirstByteLatency(MetricsAttributes attrs, Duration duration) {
-    clientCallFirstByteLatencies.record(duration.toMillis(), unwrap(attrs));
+    clientCallFirstByteLatencies.record(toMs(duration), unwrap(attrs));
   }
 
   @Override
@@ -352,6 +352,10 @@ public void recordChannelStateChange(ConnectivityState prevState, ConnectivitySt
     channelStateChangeCounter.add(1, attributes);
   }
 
+  private static double toMs(Duration duration) {
+    return duration.toNanos() / 1_000_000.0;
+  }
+
   private static Attributes unwrap(MetricsAttributes wrapped) {
     return ((MetricsAttributesImpl) wrapped).getAttributes();
   }