Spanner: closed watch-dog daemon threads spawned by Spanner client

google-cloud-clients/google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpc.java

@@ -107,6 +107,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
+import java.util.concurrent.ScheduledExecutorService;
 import javax.annotation.Nullable;
 import org.threeten.bp.Duration;
 
@@ -139,6 +140,8 @@ public class GapicSpannerRpc implements SpannerRpc {
  private final Duration checkInterval =
  systemProperty(PROPERTY_PERIOD_SECONDS, DEFAULT_PERIOD_SECONDS);
 
+ private final ScheduledExecutorService spannerWatchdog;
+
  public static GapicSpannerRpc create(SpannerOptions options) {
  return new GapicSpannerRpc(options);
  }
@@ -191,14 +194,15 @@ public GapicSpannerRpc(SpannerOptions options) {
  CredentialsProvider credentialsProvider =
  GrpcTransportOptions.setUpCredentialsProvider(options);
 
+ spannerWatchdog =
+ Executors.newSingleThreadScheduledExecutor(
+ new ThreadFactoryBuilder()
+ .setDaemon(true)
+ .setNameFormat("Cloud-Spanner-WatchdogProvider-%d")
+ .build());
  WatchdogProvider watchdogProvider =
  InstantiatingWatchdogProvider.create()
- .withExecutor(
- Executors.newSingleThreadScheduledExecutor(
- new ThreadFactoryBuilder()
- .setDaemon(true)
- .setNameFormat("Cloud-Spanner-WatchdogProvider-%d")
- .build()))
+ .withExecutor(spannerWatchdog)
  .withCheckInterval(checkInterval)
  .withClock(NanoClock.getDefaultClock());
 
@@ -572,6 +576,7 @@ public void shutdown() {
  this.spannerStub.close();
  this.instanceAdminStub.close();
  this.databaseAdminStub.close();
+ this.spannerWatchdog.shutdown();
  }
 
  /**