Re: syslogger line-end processing infelicity

Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>
>> Tom Lane wrote:
>>
>>> +1 on that. The problem of ensuring atomic output remains though
>>> (see nearby complaints from George Pavlov and others).
>>>
>
>
>> Is that the one you suggested trying to fix by calling write() instead
>> of fprintf()? If so, I can't think of any good reason not to do that
>> anyway.
>>
>
> Probably not, but it doesn't fix the problem for long log lines (more
> than PIPE_BUF bytes).
>
> The other little problem (which is the reason we like the stderr
> approach in the first place) is that not all the stderr output we want
> to capture comes from code under our control. This may not be a huge
> problem in production situations, since the main issue in my experience
> is being able to capture dynamic-linker messages when shlib loading fails.
> But it is a stumbling block in the way of any proposals that involve
> having a more structured protocol for the stuff going down the wire :-(
>
>
>

I have been trying to think of how we can get around the problem of
multiplexing our own output inappropriately. I have no great insights,
but I did think of these:

. use one pipe per backend instead of one per postmaster, and have the
syslogger poll them all.
. use a mutex to control access to the pipe
. same as previous but use a worker thread for each backend to do
logging so blocking on the mutex wouldn't block the backend

All of these look like a lot of work for a relatively infrequent
problem, not to mention plenty of other disadvantages.

cheers

andrew