hgweb: use separate repo instances per thread
Before this change, multiple threads/requests could share a
localrepository instance. This meant that all of localrepository needed
to be thread safe. Many bugs have been reported telling us that
localrepository isn't actually thread safe.
While making localrepository thread safe is a noble cause, it is a lot
of work. And there is little gain from doing so. Due to Python's GIL,
only 1 thread may be processing Python code at a time. The benefits
to multi-threaded servers are marginal.
Thread safety would be a lot of work for little gain. So, we're not
going to even attempt it.
This patch establishes a pool of repos in hgweb. When a request arrives,
we obtain the most recently used repository from the pool or create a
new one if none is available. When the request has finished, we put that
repo back in the pool.
We start with a pool size of 1. For servers using a single thread, the
pool will only ever be of size 1. For multi-threaded servers, the pool
size will grow to the max number of simultaneous requests the server
processes.
No logic for pruning the pool has been implemented. We assume server
operators either limit the number of threads to something they can
handle or restart the Mercurial process after a certain amount of
requests or time has passed.
[This file is here for historical purposes, all recent contributors
should appear in the changelog directly]
Andrea Arcangeli <andrea at suse.de>
Thomas Arendsen Hein <thomas at intevation.de>
Goffredo Baroncelli <kreijack at libero.it>
Muli Ben-Yehuda <mulix at mulix.org>
Mikael Berthe <mikael at lilotux.net>
Benoit Boissinot <bboissin at gmail.com>
Brendan Cully <brendan at kublai.com>
Vincent Danjean <vdanjean.ml at free.fr>
Jake Edge <jake at edge2.net>
Michael Fetterman <michael.fetterman at intel.com>
Edouard Gomez <ed.gomez at free.fr>
Eric Hopper <hopper at omnifarious.org>
Alecs King <alecsk at gmail.com>
Volker Kleinfeld <Volker.Kleinfeld at gmx.de>
Vadim Lebedev <vadim at mbdsys.com>
Christopher Li <hg at chrisli.org>
Chris Mason <mason at suse.com>
Colin McMillen <mcmillen at cs.cmu.edu>
Wojciech Milkowski <wmilkowski at interia.pl>
Chad Netzer <chad.netzer at gmail.com>
Bryan O'Sullivan <bos at serpentine.com>
Vicent Seguí Pascual <vseguip at gmail.com>
Sean Perry <shaleh at speakeasy.net>
Nguyen Anh Quynh <aquynh at gmail.com>
Ollivier Robert <roberto at keltia.freenix.fr>
Alexander Schremmer <alex at alexanderweb.de>
Arun Sharma <arun at sharma-home.net>
Josef "Jeff" Sipek <jeffpc at optonline.net>
Kevin Smith <yarcs at qualitycode.com>
TK Soh <teekaysoh at yahoo.com>
Radoslaw Szkodzinski <astralstorm at gorzow.mm.pl>
Samuel Tardieu <sam at rfc1149.net>
K Thananchayan <thananck at yahoo.com>
Andrew Thompson <andrewkt at aktzero.com>
Michael S. Tsirkin <mst at mellanox.co.il>
Rafael Villar Burke <pachi at mmn-arquitectos.com>
Tristan Wibberley <tristan at wibberley.org>
Mark Williamson <mark.williamson at cl.cam.ac.uk>