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 <m...@blackmans.org> wrote: > > > > On 28 Jan 2019, at 23:00, Paul B. Henson <hen...@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 > > > >
