My spring-boot application fails after start with an NPE in the tomcat server when running on azure kubernetes service with SSL.

First, what does work successfully: I have a minimal Spring-boot application created with Spring Initializr:

• Gradle project
• Java 11
• Spring Boot 2.1.8
• The only dependency: Spring Web

I want to use it with a kubernetes cluster on the azure cloud. For this, I have an Azure Kubernetes Service (AKS). And I use jib for building the docker image. Up to this point, everything works fine. I can deploy my docker image to the azure docker registry, start a kubernetes cluster (with 1 node) and I get my "hello world" after calling "http://public-ip:8443/hello". I use port 8443 but with normal http to make sure that this port is not the source of my problem.

I want my application to support HTTPS, therefore I made a self-signed certificate with keytool (like described here: Enable HTTPS with self-signed certificate in Spring Boot 2.0). This works fine on localhost. It also works inside minikube running on localhost. But when I use that docker image on AKS, my application fails a few seconds after startup.

I activated

logging.level.org.apache.tomcat=DEBUG
logging.level.org.apache.catalina=DEBUG

in my application.properties. The output of my application is:

2019-09-19 08:22:51.291  INFO 1 --- [           main] com.example.demo.DemoApplication         : Started DemoApplication in 9.623 seconds (JVM running for 10.419)
2019-09-19 08:22:53.775 DEBUG 1 --- [o-8443-Acceptor] o.apache.tomcat.util.threads.LimitLatch  : Counting up[https-jsse-nio-8443-Acceptor] latch=1
2019-09-19 08:22:58.764 DEBUG 1 --- [o-8443-Acceptor] o.apache.tomcat.util.threads.LimitLatch  : Counting up[https-jsse-nio-8443-Acceptor] latch=2
2019-09-19 08:22:58.793 DEBUG 1 --- [nio-8443-exec-1] org.apache.tomcat.util.modeler.Registry  : Managed= Tomcat:type=RequestProcessor,worker="https-jsse-nio-8443",name=HttpRequest1
2019-09-19 08:22:58.793 DEBUG 1 --- [nio-8443-exec-1] org.apache.tomcat.util.modeler.Registry  : Looking for descriptor 
2019-09-19 08:22:58.793 DEBUG 1 --- [nio-8443-exec-1] org.apache.tomcat.util.modeler.Registry  : Introspecting 
2019-09-19 08:22:58.793 DEBUG 1 --- [nio-8443-exec-1] m.m.MbeansDescriptorsIntrospectionSource : Introspected attribute virtualHost public java.lang.String org.apache.coyote.RequestInfo.getVirtualHost() null
<snipped 20 lines of "Introspected attribute xyz">
2019-09-19 08:22:58.796 DEBUG 1 --- [nio-8443-exec-1] m.m.MbeansDescriptorsIntrospectionSource : Introspected attribute lastRequestProcessingTime public long org.apache.coyote.RequestInfo.getLastRequestProcessingTime() public void org.apache.coyote.RequestInfo.setLastRequestProcessingTime(long)
2019-09-19 08:22:58.796 DEBUG 1 --- [nio-8443-exec-1] m.m.MbeansDescriptorsIntrospectionSource : Introspected attribute errorCount public int org.apache.coyote.RequestInfo.getErrorCount() public void org.apache.coyote.RequestInfo.setErrorCount(int)
2019-09-19 08:22:58.796 DEBUG 1 --- [nio-8443-exec-1] m.m.MbeansDescriptorsIntrospectionSource : Setting name: org.apache.coyote.RequestInfo
2019-09-19 08:22:58.797 DEBUG 1 --- [nio-8443-exec-1] o.a.tomcat.util.modeler.BaseModelMBean   : preRegister org.apache.coyote.RequestInfo@21c6ab25 Tomcat:type=RequestProcessor,worker="https-jsse-nio-8443",name=HttpRequest1
2019-09-19 08:22:58.797 ERROR 1 --- [nio-8443-exec-1] o.a.coyote.http11.Http11NioProtocol      : Error reading request, ignored

java.lang.NullPointerException: null
    at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.getSslSupport(NioEndpoint.java:1392) ~[tomcat-embed-core-9.0.24.jar:9.0.24]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) ~[tomcat-embed-core-9.0.24.jar:9.0.24]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1593) ~[tomcat-embed-core-9.0.24.jar:9.0.24]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.24.jar:9.0.24]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.24.jar:9.0.24]
    at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

Can anyone give me a hint what my problem might be? Thanks!