Embedded Tomcat (9.0.14 and above) is not completely shutdown / stucks when there was a (Bean-)Exception during its initialization

[stefanocke]

Spring Boot version: 2.1.2 and above (Tomcat 9.0.14 and above)

Steps to reproduce:

• Create a Spring Starter Project with Web MVC and Actuators
• Create the following Health-Endpoint:

@Component
public class ExampleHealthIndicator implements InitializingBean, HealthIndicator {

    public void afterPropertiesSet() throws Exception {
        throw new RuntimeException("Foo");
    }


    public Health health() {
        return Health.up().build();
    }

}

Expected Behavior:

• There should be some exception messages and the Spring Boot application should shutdown.

Actual Behavior:

• The Spring Boot Application does not shutdown. There are 2 remaining non-deamon threads "Catalina-utility-"

Possible Explanation:

AFAIU, there have been the following changes regarding those Catalina-Utility-threads:

• They have been made non-deamon. (See org.apache.catalina.core.StandardServer.reconfigureUtilityExecutor(int))
• Their threadpool is only shutdown, when Tomcat / Catalina is destroyed (see org.apache.catalina.core.StandardServer.destroyInternal())

In Spring Boot, the following happens:

• Tomcat is started in org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize()
• The exception occures and is catched.
• stopSilently() is called, which stops Tomcat / Catalina but does not destroy it.
• Tomcat is never destroyed, since in org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.stopAndReleaseWebServer(), this.webServer is null
• since Tomcat is never destroyed, the non-deamon thread pool for Catalina-Utility-threads is not shutdown
• the Spring Boot App never terminates

I cannot tell whether this is wrong behavior in Tomcat or whether Spring Boot has to take care about calling destroy in error case.

[wilkinsona]

Thanks for the analysis. This is a duplicate of #16892. The problem should be fixed in the latest 2.1.6 and 2.2.0 snapshots.

[stefanocke]

@wilkinsona , thank you. Great to hear.