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#!/usr/bin/env python
"""
Simple example of sending output to multiple files and
monitoring them
"""
from time import time
from select import poll, POLLIN
from subprocess import Popen, PIPE
from mininet.topo import SingleSwitchTopo
from mininet.net import Mininet
from mininet.log import info, setLogLevel
from mininet.util import decode
def monitorFiles( outfiles, seconds, timeoutms ):
"Monitor set of files and return [(host, line)...]"
devnull = open( '/dev/null', 'w' )
tails, fdToFile, fdToHost = {}, {}, {}
for h, outfile in outfiles.items():
tail = Popen( [ 'tail', '-f', outfile ],
stdout=PIPE, stderr=devnull )
fd = tail.stdout.fileno()
tails[ h ] = tail
fdToFile[ fd ] = tail.stdout
fdToHost[ fd ] = h
# Prepare to poll output files
readable = poll()
for t in tails.values():
readable.register( t.stdout.fileno(), POLLIN )
# Run until a set number of seconds have elapsed
endTime = time() + seconds
while time() < endTime:
fdlist = readable.poll(timeoutms)
if fdlist:
for fd, _flags in fdlist:
f = fdToFile[ fd ]
host = fdToHost[ fd ]
# Wait for a line of output
line = f.readline().strip()
yield host, decode( line )
else:
# If we timed out, return nothing
yield None, ''
for t in tails.values():
t.terminate()
devnull.close() # Not really necessary
def monitorTest( N=3, seconds=3 ):
"Run pings and monitor multiple hosts"
topo = SingleSwitchTopo( N )
net = Mininet( topo, waitConnected=True )
net.start()
hosts = net.hosts
info( "Starting test...\n" )
server = hosts[ 0 ]
outfiles, errfiles = {}, {}
for h in hosts:
# Create and/or erase output files
outfiles[ h ] = '/tmp/%s.out' % h.name
errfiles[ h ] = '/tmp/%s.err' % h.name
h.cmd( 'echo >', outfiles[ h ] )
h.cmd( 'echo >', errfiles[ h ] )
# Start pings
h.cmdPrint('ping', server.IP(),
'>', outfiles[ h ],
'2>', errfiles[ h ],
'&' )
info( "Monitoring output for", seconds, "seconds\n" )
for h, line in monitorFiles( outfiles, seconds, timeoutms=500 ):
if h:
info( '%s: %s\n' % ( h.name, line ) )
for h in hosts:
h.cmd('kill %ping')
net.stop()
if __name__ == '__main__':
setLogLevel('info')
monitorTest()
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