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?
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