June 2003
Intermediate to advanced
320 pages
9h 52m
English
Content preview from Tomcat: The Definitive GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 8. Debugging and Troubleshooting
Troubleshooting application servers can be intimidating. In this chapter, we show you some ways to look for information that will help you find out why things aren’t working, and give examples of mistakes we and others have made in which it was not immediately obvious where the error occurred. We also discuss why Tomcat may not shut down gracefully and what you can do about this common problem, as well as discuss ways of preventing abnormal shutdowns from recurring.
Reading Log Files
Tomcat’s logging is
quite configurable, and it is a great help in diagnosing problems.
Every element in the
server.xml
file that has a debug
attribute can be configured to log
information to log files (or to not log at all). Set the
debug attribute’s value to zero
(0) to make the object not log anything, or set it
to one (1) or a higher integer value to turn
logging on—the higher the number, the more verbose the logging
information. Set the debug level as high as you want because if
you set it to higher numbers than the object recognizes, it will just
assume you want the highest verbosity level it knows how to log.
Tip
Some objects notice log levels at 9 or potentially
higher, but most notice levels only as high as 3.
If you’re having problems with Tomcat and you’re not seeing any hints in the log files, it’s probably a good idea to turn up some of the logging levels and try again. First, make a backup copy of your server.xml file:
$ cd $CATALINA_HOME/conf $ cp ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.