CODEWITHSUNDEEP
pythonmultithreading
Spleenboy
Spleenboy

Reputation: 179

Python threads hang and don't close

This is my first try with threads in Python, I wrote the following program as a very simple example. It just gets a list and prints it using some threads. However, Whenever there is an error, the program just hangs in Ubuntu, and I can't seem to do anything to get the control prompt back, so have to restart another SSH session to get back in. Also have no idea what the issue with my program is. Is there some kind of error handling I can put in to ensure it doesn't hang. Also, any idea why ctrl/c doesn't work (I don't have a break key)

from Queue import Queue
from threading import Thread
import HAInstances
import logging

log = logging.getLogger()
logging.basicConfig()

class GetHAInstances:
    def oraHAInstanceData(self):
        log.info('Getting HA instance routing data')
        # HAData = SolrGetHAInstances.TalkToOracle.main()   
        HAData = HAInstances.main()
        log.info('Query fetched ' + str(len(HAData)) + ' HA Instances to query')
        # for row in HAData:
        # print row
        return(HAData)

def do_stuff(q):
  while True:
    print q.get()
    print threading.current_thread().name
    q.task_done()


oraHAInstances = GetHAInstances()
mainHAData = oraHAInstances.oraHAInstanceData()

q = Queue(maxsize=0)
num_threads = 10

for i in range(num_threads):
    worker = Thread(target=do_stuff, args=(q,))
    worker.setDaemon(True)
    worker.start()

for row in mainHAData:
    #print str(row[0]) + ':' +  str(row[1]) + ':' + str(row[2]) + ':' + str(row[3])i
    q.put((row[0],row[1],row[2],row[3]))

q.join()

Upvotes: 3

Views: 6250

Answers (2)

dgg32
dgg32

Reputation: 1447

In your thread method, it is recommended to use the "try ... except ... finally". This structure guarantees to return the control to the main thread even when errors occur.

def do_stuff(q):
    while True:
        try:
            #do your works
        except:
            #log the error
        finally:
            q.task_done()

Also, in case you want to kill your program, go find out the pid of your main thread and use kill #pid to kill it. In Ubuntu or Mint, use ps -Ao pid,cmd, in the output, you can find out the pid (first column) by searching for the command (second column) you yourself typed to run your Python script.

Upvotes: 2

Windspar
Windspar

Reputation: 36

Your q is hanging because your worker as errored. So your q.task_done() never got called.

import threading

to use

print threading.current_thread().name

Upvotes: 0

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