Re: [PATCH] Fix orphaned backend processes on Windows using Job Objects

On 2025-11-03 09:25:11 -0600, Bryan Green wrote:
> On 11/3/2025 9:19 AM, Andres Freund wrote:
> > Hi,
> > 
> > On 2025-11-03 09:12:03 -0600, Bryan Green wrote:
> >> We just need to call CreateJobObject() in PostmasterMain(), configure
> >> with JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE, and assign the postmaster.
> >> Children inherit membership automatically. When the job handle closes on
> >> postmaster exit, the kernel terminates all children atomically. This is
> >> kernel-enforced with no polling and no race conditions.
> > 
> > What happens if a postmaster child exits irregularly? Is postmaster terminated
> > as well?
> > 
> 
> No, Job Objects are unidirectional.

Great.


> >> The patch has been tested on Windows 10/11 with both MSVC and MinGW
> >> builds. Nested jobs fail gracefully as expected. Clean shutdown is
> >> unaffected. Crash tests with taskkill /F, debugger abort, and access
> >> violations all correctly terminate children immediately with zero orphans.
> >>
> >> This patch does not include automated tests because the core
> >> functionality (orphan prevention on crash) requires simulating process
> >> termination, which is difficult to test reliably in CI.
> > 
> > Why is it difficult to test in CI? We do some related tests in
> > 013_crash_restart.pl, it doesn't seem like it ought to be hard to also add
> > tests for postmaster?
> >
> 
> Fair point. I was hesitant because testing the actual orphan prevention
> requires killing the postmaster while backends are active, which seemed
> fragile. But you're right that we already test similar scenarios.
> 
> I can add a test to 013_crash_restart.pl (or a new Windows-specific test
> file) that:
> 1. Starts server with active backend
> 2. Kills postmaster ungracefully (taskkill /F)
> 3. Verifies backend process terminates automatically
> 4. Confirms clean restart
> 
> Would that be sufficient, or do you have other test scenarios in mind?

That's pretty much what I had in mind.

Greetings,

Andres Freund