David, On 5/14/25 3:50 PM, KARR, DAVID wrote:
I've tried several times to configure tomcat-embed-core in SpringBoot to give me better log info when Tomcat fails to start up. I thought I had this working, but apparently I was mistaken. I figured out how to get this information by stepping through the code in the debugger, when that is possible, but when the service is running in our Kubernetes clusters, that is not possible.I am presently using tomcat-embed-core 10.1.20. In the service's log file, I see this stacktrace (shortened a bit): ---------------- org.springframework.context.ApplicationContextException: Unable to start web server at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.onRefresh(ServletWebServerApplicationContext.java:165) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:618) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146) Caused by: org.springframework.boot.web.server.WebServerException: Unable to start embedded Tomcat at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:145) at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.<init>(TomcatWebServer.java:105) Caused by: java.lang.IllegalStateException: StandardEngine[Tomcat].StandardHost[localhost].TomcatEmbeddedContext[/msapi] failed to start at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.rethrowDeferredStartupExceptions(TomcatWebServer.java:207) at org.springframework.boot.web.embedded.tomcat.TomcatWebServer.initialize(TomcatWebServer.java:129) ------------- There is no other information in the previous log output that is useful. I had thought that the following steps would bridge the JUL logging to our slf4j/logback logger, but it is only partially effective. Add the following dependency information to the pom.xml: ==== <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <exclusions> <exclusion> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-logging</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-jul</artifactId> </dependency> ==== Add the following to system.properties (not in main repo): ===== java.util.logging.manager=org.apache.logging.log4j.jul.LogManager ===== In your "logback.xml" (not in main repo), add this logger: ==== <logger name="org.apache" level="ERROR" additivity="false"> <appender-ref ref="STDOUT"/> </logger> ==== With just these changes, I see no difference in the output at all. However, if I change the log level of the "org.apache" logger to TRACE, it does show some log entries from the logger whose name begins with "o.a.c." (it abbreviates the package name components to the first letter). That seems to indicate this is partially effective, but I still see no actual root cause info for the exception. It just says it failed to start up, and it doesn't say why. I have mentioned that if I can get it to fail in the same way on the desktop, I can step through the code in the debugger and inspect the actual exception that gets caught (a MultiException) and that shows the root cause. However, in the recent cases where I've been seeing this, the service doesn't fail when run on the desktop, only in our Kubernetes clusters, and I can't get to the debugger port (no matter what I set it to, apparently). Is there some critical element I'm missing in the configuration changes that would allow me to see the actual exception root cause?
Generally speaking, any exception whose stack trace is being dumped will include the "root cause", its own stack trace, and so on down the line.
This looks like a SpringBoot exception being thrown from SpringBoot code. It's up to SB to wire-in any "root cause" to the exception being thrown.
When you have enabled Tomcat logging and raised the log level (e.g. to TRACE), what are the last messages you can see in the log before the exception?
Are you able to compare that to the logs that you get on your (working) Desktop environment?
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