Debugging and Troubleshooting Mule Applications5% of the exam
Studio debugger, logging and error diagnosis
How to find the root cause of a failing Mule app: Studio breakpoints and debugger controls, remote debugging, log levels and categories in log4j2.xml, verbose and wire logging, stack traces, and reading the Mule error object.
Identify root causes for errors when debugging Mule applications, and predict outcomes.
~8 min read · 15 practice questions ·
What the exam expects
- Predict where the Studio debugger pauses (default, conditional and error breakpoints) and pick the Mule Debugger view tool that moves execution where you want it.
- Change a paused event's data and explain why the debugger never attaches to a Mule Kernel runtime.
- Start a standalone Mule server for remote debugging and state what that does to the other apps on it.
- Predict which Logger messages appear given the levels and categories in
log4j2.xml, and find each log on disk and in Studio. - Turn on verbose connector logging, HTTP wire logging and stack traces, and read the error object to name the root cause.
Key terms: error breakpoint (any processor that throws becomes a breakpoint); Run to processor (run on and stop at the selected processor); category (the Log4j 2 logger name a Logger writes through); app log versus runtime log (<app-name>.log versus mule_ee.log); error.errorMessage (the message a failing operation interpreted as an error).
Key facts
Kernel runtime
- Detail
- The Studio debugger works with EE runtimes and does not connect to Mule Kernel
Error breakpoints
- Detail
- Enabled by default; no breakpoints for one specific error type
Conditional breakpoint
- Detail
- DataWeave condition, pauses on
true, editable while the app runs
Run to processor
- Detail
- Stops at the selected processor even without a breakpoint
Remote debug scope
- Detail
- All apps on the server run in debug mode; clusters not supported
Default level
- Detail
- INFO and above, asynchronous; DEBUG and TRACE discarded
App log location
- Detail
MULE_HOME/logs/<app-name>.log; Studio shows it in the Console
Config not applied
- Detail
-M-Dlog4j.debug=trueprints whichlog4j2.xmlis used
Wire logging
- Detail
HttpMessageLoggeratDEBUG
Stack traces
- Detail
mule.verbose.exceptions=trueshows filtered stack traces
HTTP status in a handler
- Detail
error.errorMessage.attributes.statusCode
Sources for this section (9)
- Studio Debuggerdocs.mulesoft.com (opens in a new tab)
- Breakpointsdocs.mulesoft.com (opens in a new tab)
- Mule Debugger View Referencedocs.mulesoft.com (opens in a new tab)
- Server Debug Modedocs.mulesoft.com (opens in a new tab)
- Configuring Loggingdocs.mulesoft.com (opens in a new tab)
- Logger Componentdocs.mulesoft.com (opens in a new tab)
- Troubleshooting HTTP Connectordocs.mulesoft.com (opens in a new tab)
- Configuring Mule Stack Tracesdocs.mulesoft.com (opens in a new tab)
- Mule Errorsdocs.mulesoft.com (opens in a new tab)
- Why might the debugger stop pausing at throwing processors after you click Mute Breakpoints?
- When does Mule hold application execution after starting in remote debug mode?
- When does an edit to
log4j2.xmltake effect without restarting Mule? - Why would an audit trail use
LoggerandRootinstead ofAsyncLoggerandAsyncRoot?
The questions are free to read. Answers with their sources and self-grading are included with the pack.
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