feat: add keepalive changes in java client library (#409)

* feat: Add keepalive logic in bigtable data client

* fix: code formatting

* fix: mvn formatting

* fix: setting in emulator

* feat: add keep alive in enhanced stub as well

Author: sushanb

google-cloud-bigtable-emulator/src/main/java/com/google/cloud/bigtable/emulator/v2/Emulator.java

@@ -179,7 +179,13 @@ public synchronized ManagedChannel getDataChannel() {
     }
 
     if (dataChannel == null) {
-      dataChannel = newChannelBuilder(port).maxInboundMessageSize(256 * 1024 * 1024).build();
+      dataChannel =
+          newChannelBuilder(port)
+              .maxInboundMessageSize(256 * 1024 * 1024)
+              .keepAliveTimeout(10, TimeUnit.SECONDS)
+              .keepAliveTime(10, TimeUnit.SECONDS)
+              .keepAliveWithoutCalls(true)
+              .build();
     }
     return dataChannel;
   }

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/BigtableDataSettings.java

@@ -29,6 +29,7 @@
 import java.util.List;
 import java.util.logging.Logger;
 import javax.annotation.Nonnull;
+import org.threeten.bp.Duration;
 
 /**
  * Settings class to configure an instance of {@link BigtableDataClient}.
@@ -122,6 +123,10 @@ public ManagedChannelBuilder apply(ManagedChannelBuilder input) {
                         return input.usePlaintext();
                       }
                     })
+                .setKeepAliveTime(Duration.ofSeconds(10)) // sends ping in this interval
+                .setKeepAliveTimeout(
+                    Duration.ofSeconds(10)) // wait this long before considering the connection dead
+                .setKeepAliveWithoutCalls(true) // sends ping without active streams
                 .build());
 
     LOGGER.info("Connecting to the Bigtable emulator at " + hostname + ":" + port);

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/EnhancedBigtableStubSettings.java

@@ -241,6 +241,10 @@ public static InstantiatingGrpcChannelProvider.Builder defaultGrpcTransportProvi
     return BigtableStubSettings.defaultGrpcTransportProviderBuilder()
         .setPoolSize(getDefaultChannelPoolSize())
         .setMaxInboundMessageSize(MAX_MESSAGE_SIZE)
+        .setKeepAliveTime(Duration.ofSeconds(10)) // sends ping in this interval
+        .setKeepAliveTimeout(
+            Duration.ofSeconds(10)) // wait this long before considering the connection dead
+        .setKeepAliveWithoutCalls(true) // sends ping without active streams
         // TODO(weiranf): Set this to true by default once DirectPath goes to public beta
         .setAttemptDirectPath(isDirectPathEnabled());
   }