While running queue processors multithreaded will limit the
performance available to very small systems, it's easy to fix that by
adding more RAM, and previously, Zulip didn't work on such systems at
all, so this is unambiguously an improvement there.
Fixes#32.
Fixes#34.
(Commit message expanded significantly by tabbott.)
This change drops the memory used for Python processes run by Zulip in
development from about 1GB to 300MB on my laptop.
On the front of safety, http://pika.readthedocs.org/en/latest/faq.html
explains "Pika does not have any notion of threading in the code. If
you want to use Pika with threading, make sure you have a Pika
connection per thread, created in that thread. It is not safe to share
one Pika connection across threads.". Since this code only connects
to rabbitmq inside the individual threads, I believe this should be
safe.
Progress towards #32.