Claus Ibsen created CAMEL-25876:
-----------------------------------
Summary: camel-main - log why Camel Main failed to start, once,
instead of only the JVM printing it on stderr
Key: CAMEL-25876
URL: https://issues.apache.org/jira/browse/CAMEL-25876
Project: Camel
Issue Type: Improvement
Components: camel-main
Reporter: Claus Ibsen
Fix For: 4.24.0
A Camel Main application that fails to start does not log why.
{{MainSupport.run()}} passes a failure to start to the caller on purpose ("if
we have an issue starting then propagate the exception to caller"), and only
logs failures that happen while running. The main class of an application
({{main.run(args)}} in the main class of camel export, the archetypes and most
applications) does not catch it, so the exception leaves {{main()}} and only
the JVM prints it, on stderr:
{noformat}
2026-10-20 09:55:49.909 INFO 16017 --- [main]
he.camel.cli.connector.LocalCliConnector : Camel CLI connector enabled
Exception in thread "main" java.lang.reflect.InvocationTargetException
at
org.springframework.boot.loader.launch.Launcher.launch(Launcher.java:106)
...
Caused by: org.apache.camel.FailedToCreateRouteException: Failed to create
route: boom ...
{noformat}
(the launcher of the fat jar calls main by reflection, hence the
InvocationTargetException). So the log file of the application ends before the
failure. That matters in production, where an application often logs to a file,
and for camel run --runtime=main, whose log is kept as the previous run
(CAMEL-25832): camel log --previous and the AI tools of the camel-jbang-mcp
server have no reason to show.
KameletMain, which camel run uses by default, already logs it ({{doFail}}:
"Error starting Camel"). Spring Boot logs "Application run failed" and Quarkus
"Failed to start application", each once.
Proposal:
* {{MainSupport.logStartupFailure(e)}} logs "Error starting Camel: ..." with
the stack trace. {{Main}} (and so the fat-jar {{Main}} of camel export) and
{{KameletMain}} call it from {{doFail}}. It is not in the base class, as Camel
Quarkus extends {{MainCommandLineSupport}} and logs the failure itself.
* As Spring Boot does, the JVM then does not print the same failure a second
time when it leaves main: the thread that started Camel gets an uncaught
exception handler that skips the logged failure, also when it is wrapped (such
as in the InvocationTargetException of the launcher). Any other exception is
printed as before. Only when ERROR is logged, so an application without logging
still sees the failure on stderr.
_Claude Code on behalf of davsclaus_
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
