Re: Starting build-system work (Windows/Mac users please speak up)

On 05/30/20 10:42, Chapman Flack wrote:
> Diagnostic messages from Java code generally follow one of these paths:
>
> - they get explicitly sent to PostgreSQL's elog system, and go wherever
> the PostgreSQL logging is pointed, or suppressed depending on the
> enabled log level
>
> - Java exceptions caught and turned into PostgreSQL errors go into the
> PostgreSQL logs at level ERROR.
>
> - Separately, the stack traces of those exceptions are output if the
> PostgreSQL log level is set to DEBUG1 or finer. The code adjusts
> the vfprintf-hook log level (see below) to DEBUG1 before printing
> the stack trace, but I'm not positive it isn't just going to System.err
> and not through the hook. Should be easy enough to confirm, I just
> haven't had to before.

I've just confirmed this with gdb; an exception stack trace emitted
with printStackTrace [0] goes straight to System.err and the vfprintf hook
is not involved, so the surrounding calls to setJavaLogLevel aren't
really accomplishing anything.

> - Messages from the JVM itself that are emitted through a 'vfprintf hook'
> are caught by PL/Java's hook [1] and injected into PostgreSQL's
> elog system at a selectable level, usually INFO. (That is probably
> the path being followed by the -Xcheck:jni messages, explaining
> why they have INFO: in front.)

Confirmed also: -Xcheck:jni messages go through the vfprintf hook, so
they are always funneled into the PostgreSQL server log, regardless of
the setting of logging_collector.

> - Messages that are simply written to Java's System.err *can be* caught
> and included in PostgreSQL's logs, depending on PostgreSQL's
> logging_collector setting. [2] Otherwise, they just go wherever stderr
> was pointing when the PostgreSQL server was started (or wherever
> the server startup scripts point it). That could be, for example,
> the systemd journal.

-Chap

[0]
https://github.com/tada/pljava/blob/efbbc1d/pljava-so/src/main/c/JNICalls.c#L82

> [1]
> https://github.com/tada/pljava/blob/efbbc1d/pljava-so/src/main/c/Backend.c#L200
>
> [2]
> https://www.postgresql.org/docs/9.5/runtime-config-logging.html#GUC-LOGGING-COLLECTOR