NB can't stop processes which are running as children of reused mvnd daemons

[mbien]

Apache NetBeans version

Apache NetBeans 22

What happened

There is some support for mvnd since NB 13 (#3210) and generally works ok for common build tasks.

However, the stop button can cause problems under some circumstances. It terminates the process tree, the JVM may not be in the tree of the mvnd process though (unless it runs for the first time and is not a reused daemon yet). Pressing stop will kill the mvnd process (which is sometimes just the client), but the "build" will continue running in the daemon.

what works:

• pressing build, run etc and never pressing stop (let everything exit naturally)
• killing the child JVM via shell will also work since it will cause "regular" shutdown
• pressing run while having no mvnd daemons active -> stop will work since it kills the whole process tree which still includes the daemon (it seems to detach once idle)

what doesn't work / reproducer:

1. press build and wait till it finishes (there is now a daemon available)
2. press run (program runs as child of the daemon, the mvnd client process won't have any children)
3. press stop (this will kill the mvnd client process only, rest will continue running)

workaround:
run mvnd --stop before starting tasks where you expect to press stop, or clean up the processes periodically

Language / Project Type / NetBeans Component

java maven project

How to reproduce

see above

Did this work correctly in an earlier version?

No / Don't know

Operating System

linux

JDK

22.0.2, Temurin

Apache NetBeans packaging

Apache NetBeans binary zip

Anything else

No response

Are you willing to submit a pull request?

Yes (likely upstream)

[mbien]

i will likely open some cleanup PRs first, since I updated a few things while debugging this.

[mbien]

in principle, this could be fixed via a small change within mvnd and would also align with what the client already does on SIGINT (ctrl+c). (it sends a cancel message to the connected daemon which cancels the build and makes itself available again for other tasks)

here is a prototype which:

• adds a JVM shutdown hook which sends the cancel msg on irregular shutdown (SIGTERM)
• this requires to build the native image with --install-exit-handlers, since without it, GraalVM would not trigger shutdown hooks on irregular shutdowns

The problem however is that the build is also setting -H:-ParseRuntimeOptions for the purpose of delegating -D params instead of parsing them as args. This seems to mess with the signal chaining and prevents the shutdown hook from running again.

This may or may not be a graalvm bug - needs more investigation

(there are other options how to implement this, e.g the daemon could cancel builds once the client connection is gone - it all depends on the requirements)

[mbien]

upstream issues:

• [GR-34103] Shutdown hooks not called when -H:-ParseRuntimeOptions is set oracle/graal#9568
• Cancel job on client TERM signal maven-mvnd#1112