perl-modperl mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From John Deighan <john.deig...@gmail.com>
Subject Re: HTTP and MPM support
Date Tue, 29 Jan 2019 14:38:59 GMT
We also use threads without any problem in production. Main use is sharing
caches so that multiple mod_perl interpreters don'teach store the same
cached information. Following a few simple and documented rules, we've had
no issues with using threads.

On Mon, Jan 28, 2019 at 6:18 PM Mark Blackman <mark@blackmans.org> wrote:

>
>
> > On 28 Jan 2019, at 23:00, Paul B. Henson <henson@acm.org> wrote:
> >
> > On 1/28/2019 1:53 PM, Mark Blackman wrote:
> >> https://perldoc.perl.org/threads.html#WARNING  Threads are discouraged
> in Perl these days
> >
> > Yes, that is indeed what the documentation says; however, there is a far
> cry between "Perl is single-threaded by design and history and has no
> reliable support for threading" and "use of threads is discouraged in perl".
> >
> > Looking back to the original discussion that led to that caveat
> https://www.nntp.perl.org/group/perl.perl5.porters/2014/03/msg213382.html
> a good summary of why it is there is:
> >
> > "The patch came about because unmanaged expectations of support are
> causing social problems"
> >
> > And further discussion about it
> https://www.perlmonks.org/?node_id=1107534 has a similar insight:
> >
> > "that this particular formulation is just smoke and mirrors to repel
> 'annoying newbies"
> >
> > Then in this bug discussing the verbiage
> https://rt.perl.org/Public/Bug/Display.html?id=133021 a developer
> comments:
> >
> > "The fact is that threads work, they are maintained, and they currently
> do not have any bugs preventing their use."
> >
> > Basically, perl threads are heavyweight, not lightweight, and use of
> non-thread safe Perl code whether your own or in third-party modules will
> cause potentially nondeterministic problems. The warning is basically there
> to scare away people who don't have sufficient expertise to make it work
> and will likely come complain and ask for help with something the
> developers don't want to have to explain over and over again.
> >
> > Back when I was running DCE/DFS and maintaining the perl modules on top
> of that, I used threaded perl heavily with no issues. As long as the
> mechanism of and caveats regarding Perl threads are understood, and there
> is a justifiable reason to be using them rather than some other construct,
> discouraged is not deprecated nor unavailable/unreliable.
>
> "Threads are implemented in a way that make them easy to misuse." ==
> "single threaded by design” in my book, but your mileage may vary. I
> believe threads were retrofitted to Perl and I see very little use of
> threads in the wild myself. Relying on threads in Perl with real-world
> third-party XS modules that aren’t thread-safe is equivalent to unreliable.
> Base Perl might be safe enough, but nobody runs real-world apps with pure
> Perl alone IME.
>
> I am glad you made threads work well in production, but I suspect you’re
> in a minority.
>
> - Mark
>
>
>
>

Mime
View raw message