Re: CI/windows docker vs "am a service" autodetection on windows

Hi,

Magnus, Michael, Anyone - I'd appreciate a look.

On 2021-03-05 12:55:37 -0800, Andres Freund wrote:
> > After fighting with a windows VM for a bit (ugh), it turns out that yes,
> > there is stderr, but that fileno(stderr) returns -2, and
> > GetStdHandle(STD_ERROR_HANDLE) returns NULL (not INVALID_HANDLE_VALUE).
> >
> > The complexity however is that while that's true for pg_ctl within
> > pgwin32_ServiceMain:
> > checking what stderr=00007FF8687DFCB0 is (handle: 0, fileno=-2)
> > but not for postmaster or backends
> > WARNING: 01000: checking what stderr=00007FF880F5FCB0 is (handle: 92, fileno=2)
> >
> > which makes sense in a way, because we don't tell CreateProcessAsUser()
> > that it should pass stdin/out/err down (which then seems to magically
> > get access to the "topmost" console applications output - damn, this
> > stuff is weird).
>
> That part is not too hard to address - it seems we only need to do that
> in pg_ctl pgwin32_doRunAsService(). It seems that the
> stdin/stderr/stdout being set to invalid will then be passed down to
> postmaster children.
>
> https://docs.microsoft.com/en-us/windows/console/getstdhandle
> "If an application does not have associated standard handles, such as a
> service running on an interactive desktop, and has not redirected them,
> the return value is NULL."
>
> There does seem to be some difference between what services get as std*
> - GetStdHandle() returns NULL, and what explicitly passing down invalid
> handles to postmaster does - GetStdHandle() returns
> INVALID_HANDLE_VALUE. But passing down NULL rather than
> INVALID_HANDLE_VALUE to postmaster seems to lead to postmaster
> re-opening console buffers.
>
> Patch attached.

> I'd like to commit something to address this issue to master soon - it
> allows us to run a lot more tests in cirrus-ci... But probably not
> backpatch it [yet] - there've not really been field complaints, and who
> knows if there end up being some unintentional side-effects...

Because it'd allow us to run more tests as part of cfbot and other CI
efforts, I'd like to push this forward. So I'm planning to commit this
to master soon-ish, unless somebody wants to take this over? I'm really
not a windows person...

Greetings,

Andres Freund