fix: logs and plumb metric sink

Author: AgraVator

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

@@ -56,6 +56,8 @@ final class TcpMetrics {
     } catch (Error e) {
       log.log(Level.FINE, "Failed to load native Epoll library", e);
     }
+    log.log(Level.INFO, "Epoll available during static init of TcpMetrics:"
+        + "{0}", epollAvailable);
     DEFAULT_METRICS = new Metrics(epollAvailable);
   }
 
@@ -198,8 +200,15 @@ void recordTcpInfo(Channel channel) {
     }
 
     private void recordTcpInfo(Channel channel, boolean isClose) {
-      if (epollSocketChannelClass == null
-          || !epollSocketChannelClass.isInstance(channel)) {
+      if (epollSocketChannelClass == null) {
+        log.log(Level.FINE, "Skipping recordTcpInfo because"
+            + "epollSocketChannelClass is null");
+        return;
+      }
+      if (!epollSocketChannelClass.isInstance(channel)) {
+        log.log(Level.FINE, "Skipping recordTcpInfo because channel is not an"
+            + "instance of epollSocketChannelClass: {0}", channel.getClass()
+            .getName());
         return;
       }
       List<String> labelValues = getLabelValues(channel);

opentelemetry/src/main/java/io/grpc/opentelemetry/GrpcOpenTelemetry.java

@@ -196,6 +196,7 @@ public void configureServerBuilder(ServerBuilder<?> serverBuilder) {
       serverBuilder.intercept(openTelemetryTracingModule.getServerSpanPropagationInterceptor());
     }
     serverBuilder.addStreamTracerFactory(openTelemetryMetricsModule.getServerTracerFactory());
+    serverBuilder.addMetricSink(sink);
   }
 
   @VisibleForTesting