Re: Unfiltered server logs routing via a new elog hook or existing emit_log_hook bypassing log_min_message check - Mailing list pgsql-hackers

From Julien Rouhaud
Subject Re: Unfiltered server logs routing via a new elog hook or existing emit_log_hook bypassing log_min_message check
Date
Msg-id 20220502130241.ejo5bau5sfu52jhr@jrouhaud
Whole thread Raw
In response to Unfiltered server logs routing via a new elog hook or existing emit_log_hook bypassing log_min_message check  (Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>)
Responses Re: Unfiltered server logs routing via a new elog hook or existing emit_log_hook bypassing log_min_message check
List pgsql-hackers
Hi,

On Mon, May 02, 2022 at 05:11:34PM +0530, Bharath Rupireddy wrote:
>
> Currently the emit_log_hook gets called only for the log messages of
> type <= log_min_message i.e when edata->output_to_server is true [1],
> which means that I can't use an implementation of emit_log_hook to
> just intercept, say, all DEBUGX messages without interrupting the
> actual server logs flow and changing the log_min_message.
> [...]
> If I had
> postgres elog hook, say emit_unfiltered_log_hook [2], I can basically
> write an external module (with a bunch of GUCs say log_level to route,
> place to store the logs, even an option to filter logs based on text
> say logs containing word 'replication', max disk space that these
> routed logs would occupy etc.) implementing emit_unfiltered_log_hook
> to just route the interested logs to a cheaper storage (for debugging
> purposes), after analysis I can disable the external module and blow
> away the routed logs.

Unless I'm missing something you can already do all of that with the current
hook, since as mentioned in the comment above the hook can disable the server's
logging:

     * Call hook before sending message to log.  The hook function is allowed
     * to turn off edata->output_to_server, so we must recheck that afterward.

So you can configure your server with a very verbose log_min_message, and have
the same setting in your own extension to disable output_to_server after its
own processing is done.



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