A PYTHON APPLICATION WHERE THREADS WOULD HELP

Let's say that you want to check the availability of many computers on a network ... you'll use ping. But there's a problem - if you "ping" a host that's not running it takes a while to timeout, so that when you check through a whole lot of systems that aren't responding - the very time a quick response is probably needed - it can take an age.

Here's a Python program that "ping"s 10 hosts in sequence.

import os
import re
import time
import sys

lifeline = re.compile(r"(\d) received")
report = ("No response","Partial Response","Alive")

print time.ctime()

for host in range(60,70):
ip = "192.168.200."+str(host)
pingaling = os.popen("ping -q -c2 "+ip,"r")
print "Testing ",ip,
sys.stdout.flush()
while 1:
line = pingaling.readline()
if not line: break
igot = re.findall(lifeline,line)
if igot:
print report[int(igot[0])]

print time.ctime()

Running that program, it works but it's a bit slow:

[trainee@buttercup trainee]$ python alive
Mon May 9 05:22:51 2005
Testing 192.168.200.60 No response
Testing 192.168.200.61 No response
Testing 192.168.200.62 No response
Testing 192.168.200.63 No response
Testing 192.168.200.64 No response
Testing 192.168.200.65 No response
Testing 192.168.200.66 Alive
Testing 192.168.200.67 No response
Testing 192.168.200.68 No response
Testing 192.168.200.69 No response
Mon May 9 05:23:19 2005
[trainee@buttercup trainee]$

That was 28 seconds - in other words, an extra 3 seconds per unavailable host.

THE SAME APPLICATION, WRITTEN USING PYTHON THREADS

I'll write the application and test it first ... then add a few notes at the bottom.

import os
import re
import time
import sys
from threading import Thread

class testit(Thread):
def __init__ (self,ip):
Thread.__init__(self)
self.ip = ip
self.status = -1
def run(self):
pingaling = os.popen("ping -q -c2 "+self.ip,"r")
while 1:
line = pingaling.readline()
if not line: break
igot = re.findall(testit.lifeline,line)
if igot:
self.status = int(igot[0])

testit.lifeline = re.compile(r"(\d) received")
report = ("No response","Partial Response","Alive")

print time.ctime()

pinglist = []

for host in range(60,70):
ip = "192.168.200."+str(host)
current = testit(ip)
pinglist.append(current)
current.start()

for pingle in pinglist:
pingle.join()
print "Status from ",pingle.ip,"is",report[pingle.status]

print time.ctime()

And running:

[trainee@buttercup trainee]$ python kicking
Mon May 9 05:23:36 2005
Status from 192.168.200.60 is No response
Status from 192.168.200.61 is No response
Status from 192.168.200.62 is No response
Status from 192.168.200.63 is No response
Status from 192.168.200.64 is No response
Status from 192.168.200.65 is No response
Status from 192.168.200.66 is Alive
Status from 192.168.200.67 is No response
Status from 192.168.200.68 is No response
Status from 192.168.200.69 is No response
Mon May 9 05:23:39 2005
[trainee@buttercup trainee]$

3 seconds - much more acceptable than the 28 seconds that we got when we pinged the hosts one by one and waited on each.

http://www.wellho.net/solutions/python-python-threads-a-first-example.html