Spark in Yarn Cluster Mode - Yarn client reports FAILED even when job completes successfully - apache-spark

Question

I am experimenting with running Spark in yarn cluster mode (v2.3.0). We have traditionally been running in yarn client mode, but some jobs are submitted from .NET web services, so we have to keep a host process running in the background when using client mode (HostingEnvironment.QueueBackgroundWorkTime...). We are hoping we can execute these jobs in a more "fire and forget" style.
Our jobs continue to run successfully, but we see a curious entry in the logs where the yarn client that submits the job to the application manager is always reporting failure:
18/11/29 16:54:35 INFO yarn.Client: Application report for application_1539978346138_110818 (state: RUNNING)
18/11/29 16:54:36 INFO yarn.Client: Application report for application_1539978346138_110818 (state: RUNNING)
18/11/29 16:54:37 INFO yarn.Client: Application report for application_1539978346138_110818 (state: FINISHED)
18/11/29 16:54:37 INFO yarn.Client:
client token: Token { kind: YARN_CLIENT_TOKEN, service: }
diagnostics: N/A
ApplicationMaster host: <ip address>
ApplicationMaster RPC port: 0
queue: root.default
start time: 1543510402372
final status: FAILED
tracking URL: http://server.host.com:8088/proxy/application_1539978346138_110818/
user: p800s1
Exception in thread "main" org.apache.spark.SparkException: Application application_1539978346138_110818 finished with failed status
at org.apache.spark.deploy.yarn.Client.run(Client.scala:1153)
at org.apache.spark.deploy.yarn.YarnClusterApplication.start(Client.scala:1568)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:892)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:197)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:227)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:136)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
18/11/29 16:54:37 INFO util.ShutdownHookManager: Shutdown hook called
We always create a SparkSession and always return sys.exit(0) (although that appears to be ignored by the Spark framework regardless of how we submit a job). We also have our own internal error logging that routes to Kafka/ElasticSearch. No errors are reported during the job run.
Here's an example of the submit command: spark2-submit --keytab /etc/keytabs/p800s1.ktf --principal p800s1#OURDOMAIN.COM --master yarn --deploy-mode cluster --driver-memory 2g --executor-memory 4g --class com.path.to.MainClass /path/to/UberJar.jar arg1 arg2
This seems to be harmless noise, but I don't like noise that I don't understand. Has anyone experienced something similar?