Hi all,
I'm new to asyncio introduced by Python 3.4. I created two tasks each pings
a host. I noticed some pieces of output will be lost(see "error: found icmp_seq
gap"). If I changed to run only one task, this problem never occur.
Do you have any idea?
Thanks!
Zhichang
zhichyu@cto-team-6:~$ python3 asyn2.py
got line: b'PING tyr.global.tektronix.net (10.250.163.252) 56(84) bytes of
data.\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=2
ttl=55 time=204 ms\n'
got line: b'PING babylon.rich.tek.com (10.250.155.123) 56(84) bytes of data.\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=2
ttl=55 time=205 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=3
ttl=55 time=205 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=3
ttl=55 time=205 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=4
ttl=55 time=196 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=4
ttl=55 time=198 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=5
ttl=55 time=181 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=5
ttl=55 time=182 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=6
ttl=55 time=180 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=6
ttl=55 time=179 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=7
ttl=55 time=193 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=7
ttl=55 time=196 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=8
ttl=55 time=185 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=8
ttl=55 time=187 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=9
ttl=55 time=213 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252): icmp_seq=9
ttl=55 time=211 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=10
ttl=55 time=192 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252):
icmp_seq=10 ttl=55 time=192 ms\n'
got line: b'64 bytes from tyr.global.tektronix.net (10.250.163.252):
icmp_seq=11 ttl=55 time=210 ms\n'
got line: b'64 bytes from babylon.rich.tek.com (10.250.155.123): icmp_seq=12
ttl=55 time=210 ms\n'
error: found icmp_seq gap!
zhichyu@cto-team-6:~$ cat asyn2.py
#!/usr/bin/env python3.4
'''
refers to
*
http://stackoverflow.com/questions/375427/non-blocking-read-on-a-subprocess-pipe-in-python/20697159#20697159
* 18.5.3.5.1. Example: Parallel execution of tasks
'''
import asyncio
import sys
import signal
import time
import re
from asyncio.subprocess import PIPE
from contextlib import closing
from functools import partial
icmp_seq = re.compile(b'icmp_seq=(?P<seq>\d+)')
@asyncio.coroutine
def ping(*args, max_line_size=1<<20, timeout=None, loop=None):
if loop is None:
loop = asyncio.get_event_loop()
with_timeout = partial(asyncio.wait_for, timeout=timeout, loop=loop)
# start child process
process = yield from asyncio.create_subprocess_exec(*args, stdout=PIPE,
stderr=PIPE, limit=max_line_size, loop=loop)
try:
seq = 0
begin = loop.time()
while(True):
# read line (sequence of bytes ending with b'\n') asynchronously
#line = yield from with_timeout(process.stdout.readline())
line = yield from process.stdout.readline()
print("got line:", line)
sys.stdout.flush()
m = icmp_seq.search(line)
if(m):
seq2 = int(m.group('seq'))
if(seq!=0 and seq2!=seq + 1):
loop.stop()
print('error: found icmp_seq gap!')
break
seq = seq2
now = loop.time()
if(now - begin > 1000):
break
finally:
'''
process.kill()
rc = yield from with_timeout(process.wait())
'''
process.send_signal(signal.SIGTERM)
(stdoutdata, stderrdata) = yield from
with_timeout(process.communicate())
print("final stdout:", stdoutdata)
print("final stderr:", stderrdata)
rc = process.returncode
return rc
#NOTE: use ProactorEventLoop on Windows as shown in the previous example
with closing(asyncio.get_event_loop()) as loop:
# Some lines will be lost if running multiple tasks. Why?
task1 = asyncio.async(ping("ping", "tyr.global.tektronix.net", timeout=5,
loop=loop))
task2 = asyncio.async(ping("ping", "babylon.rich.tek.com", timeout=5,
loop=loop))
tasks = [task1, task2]
rc = loop.run_until_complete(asyncio.wait(tasks))
sys.exit(rc)
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