Add logs to confirm JvmInitializer completed running and Spanner succ…

…essfully connected. (apache#29727)

* Add logs to confirm JvmInitializer completed running.

* Add log to confirm Spanner successfully connected.

sdks/java/fn-execution/src/main/java/org/apache/beam/sdk/fn/JvmInitializers.java

@@ -35,6 +35,7 @@ public static void runOnStartup() {
       // We write to standard out since logging has yet to be initialized.
       System.out.format("Running JvmInitializer#onStartup for %s%n", initializer);
       initializer.onStartup();
+      System.out.format("Completed JvmInitializer#onStartup for %s%n", initializer);
     }
   }
 
@@ -52,6 +53,7 @@ public static void runBeforeProcessing(PipelineOptions options) {
     for (JvmInitializer initializer : ReflectHelpers.loadServicesOrdered(JvmInitializer.class)) {
       logger.info("Running JvmInitializer#beforeProcessing for {}", initializer);
       initializer.beforeProcessing(options);
+      logger.info("Completed JvmInitializer#beforeProcessing for {}", initializer);
     }
   }
 }

sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/spanner/SpannerAccessor.java

@@ -98,6 +98,7 @@ public static SpannerAccessor getOrCreate(SpannerConfig spannerConfig) {
           // Connect to spanner for this SpannerConfig.
           LOG.info("Connecting to {}", spannerConfig);
           self = SpannerAccessor.createAndConnect(spannerConfig);
+          LOG.info("Successfully connected to {}", spannerConfig);
           spannerAccessors.put(spannerConfig, self);
           refcounts.putIfAbsent(spannerConfig, new AtomicInteger(0));
         }