Develop Reference

Python multithreading- memory leak when use an shared object(so)

I have a python programs that gets memory leaks when use an third-party SO.
I simplify my code like this:
import time
import sys
import threading
import codecs
import ctypes
sys.stdout = codecs.getwriter("utf-8")(sys.stdout.detach())
class TestThirdPartySo(object):
def __init__(self):
# this so uses thread-specific data
self.call_stat_so = ctypes.CDLL("./third_party_fun.so")
self.handle = self.call_stat_so._handle
def test_fun(self):
self.call_stat_so.fun_xxx()
def thread_fun():
TestThirdPartySo().test_fun()
def test_main(num):
count = 0
while True:
# create 3 * num threads
thread_num = 3
thread_list = []
for _ in range(thread_num):
thread_list.append(threading.Thread(target=thread_fun))
for thread in thread_list:
thread.start()
for thread in thread_list:
thread.join()
count += thread_num
time.sleep(0.01)
if count % 100 == 0:
print("finied %s" % count)
if count > num:
break
print("end !!!!")
if __name__ == '__main__':
num = sys.argv[1]
test_main(int(num))
Now, I know this shared object uses thread-specific data.And I have tried to close the SO after called it like this:
class TestThirdPartySo(object):
def __init__(self):
# this so uses thread-specific data
self.call_stat_so = ctypes.CDLL("./third_party_fun.so")
self.handle = self.call_stat_so._handle
def test_fun(self):
self.call_stat_so.fun_xxx()
def __del__(self):
dlclose_func(self.handle)
def dlclose_func(_handle):
dlclose_func_tmp = ctypes.cdll.LoadLibrary('libdl.so').dlclose
dlclose_func_tmp.argtypes = [ctypes.c_void_p]
dlclose_func_tmp(_handle)
But I failed to close the so. And I'm also not sure if the leaked memory will be freed after closing the so.
If the program not uses multi-threads or creates a fixed number of threads(threadpool), it works ok.
For some reason,I need create threads constantly in my program. What can I do to prevent this memory leaks?

How to fix this basic example of threading in Python

I am trying to teach myself how to use threading in Python. I have come up with the basic problem of trying to interrupt a function that would continue printing the square of a number forever after only 10 seconds. I used this website as an example: http://zulko.github.io/blog/2013/09/19/a-basic-example-of-threads-synchronization-in-python/. The code that I have now does not work as intended and I'm wondering if any of you could help me fix it so I can understand threading better. Thank you in advance!
import threading
import time
def square(x):
while 1==1:
time.sleep(5)
y=x*x
print y
def alarm():
time.sleep(10)
go_off.set()
def go():
go_off= threading.Event()
squaring_thread = threading.Thread(target=square, args = (go_off))
squaring_thread.start()
square(5)
go()

import threading
import time
#Global scope to be shared across threads
go_off = threading.Event()
def square(x):
while not go_off.isSet():
time.sleep(1)
print x*x
def alarm():
time.sleep(10)
go_off.set()
def go():
squaring_thread = threading.Thread(target=square,args = (6,))
alarm_thread = threading.Thread(target=alarm , args = ())
alarm_thread.start()
squaring_thread.start()
go()

Regularly check whether a webserver is up with a Thread

I wrote a Threading class which tests whether a webserver is up or not.
import urllib
import threading
import time
import Queue
class Thread_CheckDeviceState(threading.Thread):
def __init__(self, device_ip, queue, inter=0.1):
self._run = True
self._codes = {}
self._queue = queue
self._device_ip = device_ip
self._inter = inter
self._elapsed = 0
threading.Thread.__init__(self)
def stop(self):
self._run = False
def run(self):
start = time.time()
while self._run:
try:
code = urllib.urlopen(self._device_ip).getcode()
except Exception:
code = "nope"
finally:
measure = time.time()
self._elapsed += measure-start
print self._elapsed, code
self._codes.update(
{self._elapsed:code}
)
time.sleep(self._inter)
self._queue.put(self._codes)
q = Queue.Queue()
thread = Thread_CheckDeviceState("http://192.168.1.3", q)
thread.start()
time.sleep(10)
thread.stop()
print q.get()
It works fine - until I disconnect my pc from the network. From that moment on the thread just does nothing until it is stopped. I would expect it to just continue and set the code to "nope", like I wrote it in the exception handler. Why doesn't it work

You need to use urllib2 instead, and specify a timeout parameter when you call urlopen().

How to communicate with multiple servers using the single class defined in python and run it parallel

I have a python class that communicates with a server. That python class has many functions, i was using few functions. But i want to access multiple servers data at same time using the python class i have.
Am trying something like this, but it'll run one after the other. And i wanted to get the data at same time.
import threading
from server_class import server
class runMonitor(threading.Thread):
def __init__(self,func):
self.func = func
threading.Thread.__init__(self)
def run(self):
self.func()
def monitorSB(ipAddr):
sb = server(ipAddr)
sb.readInfo()
print ('\nReading Registers...\n')
sb.read_rx()
sb.read_tx()
i = 0
while(1):
if i == 0:
print 'Monitoring Registers...'
i = 1
sb.monitor_tx()
sb.monitor_rx()
t = runMonitor(monitorSB('192.168.10.78'))
q = runMonitor(monitorSB('192.168.10.101'))
t.start()
q.start()
print ('\nTest Done...\n')
In the above code, i wanted to access both servers at same time. Help me how to run in parallel

The thing is by saying monitorSB('192.168.10.78') it will execute it before passing it to your thread. Try this:
import threading
from server_class import server
class runMonitor(threading.Thread):
def __init__(self,func, param):
self.func = func
self.param = param
threading.Thread.__init__(self)
def run(self):
self.func(self.param)
def monitorSB(ipAddr):
sb = server(ipAddr)
sb.readInfo()
print ('\nReading Registers...\n')
sb.read_rx()
sb.read_tx()
i = 0
while(1):
if i == 0:
print 'Monitoring Registers...'
i = 1
sb.monitor_tx()
sb.monitor_rx()
t = runMonitor(monitorSB, '192.168.10.78')
q = runMonitor(monitorSB, '192.168.10.101')
t.start()
q.start()
print ('\nTest Done...\n')

python multiprocessing process count

#coding:utf-8
import sys
import time
import os
import multiprocessing
class Worker(object):
def __init__(self):
self.progress = 0
self.task_info = None
def init(self):
pass
def status(self):
pass
def set_task_info(self, task_info):
self.task_info = task_info
def run(self, worker_status_meta_dict):
print multiprocessing.current_process()
print "process is %d" % self.progress
while self.progress < 5:
self.progress = self.progress +1
worker_status_meta_dict['state'] = 0
worker_status_meta_dict['status'] = "running"
time.sleep(2)
worker_status_meta_dict['state'] = 1
worker_status_meta_dict['status'] = "succeeded"
print "bavscan worker finished..."
if __name__ == "__main__":
worker = Worker()
worker_process_dict = multiprocessing.Manager().dict()
process = multiprocessing.Process(target=Worker.run, args=(worker, worker_process_dict))
process.start()
time.sleep(60)
This is a simple demo for python multiprocess.
The main process invoke the Worker.run method in a subprocess with multiprocessing.Process.
When run it in wondows 7, the main process will lauch two subprocess.

I find the problem in the "Python27\Lib\multiprocessing__init__.py"
def Manager():
'''
Returns a manager associated with a running server process
The managers methods such as `Lock()`, `Condition()` and `Queue()`
can be used to create shared objects.
'''
from multiprocessing.managers import SyncManager
m = SyncManager()
m.start()
return m
m.start() will lauch a subprocess to start the manager.