Re: Proposal: More structured logging

Le mercredi 1 septembre 2021, 09:36:50 CEST Peter Eisentraut a écrit :
> On 13.08.21 15:23, Ronan Dunklau wrote:
> > The logging system already captures a lot of information in the ErrorData.
> > But at present there is no way for a log message authors to include more
> > metadata about the log outside of the log message itself. For example,
> > including the extension name which can be useful for filtering /
> > dispatching log messages. This can be done in the log message itself, but
> > that requires specialized parsing in the log output.
> >
> > Even though among the available loggers in core, only the csv logger would
> > be able to make sense of it, I feel it would be beneficial to add a
> > tagging system to logs, by adding different (tag, value) combinations to
> > a log entry, with an API similar to what we do for other ErrorData
> > fields:
> >
> > ereport(NOTICE,
> >
> > (errmsg("My log message")),
> > (errtag("EMITTER", "MYEXTENSION")),
> > (errtag("MSG-ID", "%d", error_message_id))
> >
> > );
>
> What are some more examples of where this could be used? The extension
> name could be added more or less automatically to ereport() calls. I
> don't know what the MSG-ID is supposed to be. Are there other use cases?

Adding it automatically would be nice, but how would you go about that ?

In-core it would open up the possibility to split log messages into different
fields, for example the different statistics reported in the logs by VACUUM /
ANALYZE VERBOSE and make it easier to consume the output without having to
parse the message. Parsing the message also means that any tool parsing it
needs to either be aware of the locale, or to force the user to use a specific
one.

Out-of-core, the same things could be done for extensions like pg_audit which
logs structured information into the message itself, leaving the message
format to be parsed at a later time.

--
Ronan Dunklau