Miguel P <prosper.spur...@gmail.com> wrote:
> On Sep 12, 2:54 pm, Ned Deily <n...@acm.org> wrote:
> > In article
> > <da2362e0-ec68-467b-b50b-6067057d7...@y36g2000yqh.googlegroups.com>,
> > Miguel P <prosper.spur...@gmail.com> wrote:
> > > I've been working on parsing (tailing) a named pipe which is the
> > > syslog output of the traffic for a rather busy haproxy instance. It's
> > > a fair bit of traffic (upto 3k hits/s per server), but I am finding
> > > that simply tailing the file in python, without any processing, is
> > > taking up 15% of a CPU core. In contrast HAProxy takes 25% and syslogd
> > > takes 5% with the same load. `cat < /named.pipe` takes 0-2%
> >
> > > Am I just doing things horribly wrong or is this normal?
> >
> > > Here is my code:
> >
> > > from collections import deque
> > > import io, sys
> >
> > > WATCHED_PIPE = '/var/log/haproxy.pipe'
> >
> > > if __name__ == '__main__':
> > > try:
> > > log_pool = deque([],10000)
> > > fd = io.open(WATCHED_PIPE)
> > > for line in fd:
> > > log_pool.append(line)
> > > except KeyboardInterrupt:
> > > sys.exit()
> >
> > > Deque appends are O(1) so that's not it. And I am using 2.6's io
> > > module because it's supposed to handle named pipes better. I have
> > > commented the deque appending line and it still takes about the same
> > > CPU.
> >
> > Be aware that the io module in Python 2.6 is written in Python and was
> > viewed as a prototype. In the current svn trunk, what will be Python
> > 2.7 has a much faster C implementation of the io module backported from
> > Python 3.1.
>
> Aha, I will test with trunk and see if the performance is better, if
> so I'll use 2.6 in production until 2.7 comes out. I will report back
> when I have made the tests.
Why don't you try just using the builtin open() with bufsize
parameter set big?
Something like this (tested with named pipes). Tweak BUFFERSIZE and
SLEEP_INTERVAL for maximum performance!
import time
BUFFERSIZE = 1024*1024
SLEEP_INTERVAL = 0.1
def tail(path):
fd = open(path)
buf = ""
while True:
buf += fd.read(BUFFERSIZE)
if buf:
lines = buf.splitlines(True)
for line in lines[:-1]:
yield line
buf = lines[-1]
if buf.endswith("\n"):
yield buf
buf = ""
else:
time.sleep(SLEEP_INTERVAL)
def main(path):
for line in tail(path):
print "%r:%r" % (len(line), line)
if __name__ == "__main__":
import sys
main(sys.argv[1])
--
Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick
--
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