On 5/18/12 12:21 AM, William Stein wrote:
On Thu, May 17, 2012 at 10:08 PM, Jason Grout
<jason-s...@creativetrax.com> wrote:
I upgraded the Sage servers to 5.0, and it seems that there is some sort of
really bad scalability problem that I'm only seeing on sagenb.org (or more
likely, is only noticeable on a server the size of sagenb.org). Some of you
may have noticed that sagenb.org has been unbearably slow the last few
hours. Just FYI, it will be up and down for the next little bit while I try
to diagnose the problem.
Thanks,
Jason
For those interested, it seems that the web server twisted process is pegged
at 100% cpu and doesn't back down. Requests seem to work, but you have to
wait for minutes for a reply.
I'm guessing you might try one of:
(1) switching from using twisted to flask's server -- we do *not*
need twisted, since we aren't using SSL, and flask is multithreaded.
Make sure to run flask with debug=False and threaded=True.
Any idea of how our locking would work with multithreaded flask? It
seems like it should be fine, but still...
(2) Use an older version of twisted?
Good idea, except that we seem to have the same problem with the old 4.8
installation, that seemed to work fine before. I profiled the 5.0
server for several hours and the profile logs are in /sagenb/profile*.
If someone wants to take a crack at diagnosing, feel free to get those
logs (they are the pstats.Stats logs, so you load it with
import pstats
pstats.Stat('filename')
It does seem to me like the problems are in threads acquiring locks and
possibly sending/receiving data. Maybe switching to the multithreaded
flask server might help. For the record, all the other *.sagenb.org
servers are switched over to 5.0 and seem like they are working fine.
For now, I switched sagenb.org back to the 4.8 server, which hopefully
will become responsive soon enough. I'm pretty much offline for a day
or two, but will work on this more Monday morning.
Thanks,
Jason
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