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Python question regarding a server listener

Answer 1

A:

Python actually has a threading system that is fairly similar to Java, so you should be able to use that without much trouble.

But if all you need to do is wait for some predetermined amount of time, use

import time
time.sleep(300) # sleep for 300 seconds

David Zaslavsky 2009-08-20 17:06:40

This is somewhat what I was thinking, but I just don't know how much time that is. My original thought was to do this same time.sleep() command for so many seconds and try to locate the file. And if it returns the http 404 error then sleep for another so many seconds and try again. This just seems like and ugly approach, and I was hoping for a more elegant solution.

cozmokramer8 2009-08-20 17:23:14

Oh and thanks for the link too, I am reading through that now. :)

cozmokramer8 2009-08-20 17:24:16

@cozmokramer8: It's called "polling" or "busy waiting" and it's your only choice in this case.

S.Lott 2009-08-20 17:38:10

Answer 2

+2 A:

Unless you get get notified by having the build server contact you, the only way to do it is to poll. You can either spawn a thread as indicated in other comments, you just have your main script sleep and poll.

Something like:

wait=True
while wait:
   url=urllib.urlopen('http://'+username+':'+password+'@localhost/httpAuth/action.html?add2Queue='+btid+'&amp;system.name=&lt;btid&gt;&amp;system.value=&lt;'+btid+'&gt;&amp;system.name=&lt;buildNumber&gt;&amp;system.value=&lt;'+buildNumber+'&gt;')
   if url.getcode()!=404:
     wait=False
   else:
     time.sleep(60)

As an alternative, you could use CherryPy. Then, when the build is done, you could have curl or wget connect to the listening CherryPy server and trigger your app to download the url.

You could also use xmlrpclib to do something similar.

Christopher 2009-08-20 17:47:37

I guess I am going to have to poll then. I liked your suggestions for alternatives, but I am somewhat limited because I have to use only what is currently installed on the server. This is for a fairly big company and I don't have the option of even installing extra python libs :( Thanks for the code though. Just curious is this considered bad coding practice to do it this way? It seems ugly to me but apparently it must happen quite often. Thanks again Grant

cozmokramer8 2009-08-20 17:58:55

The question of interrupt-driven or poll-based notification is a large one. Sometimes polling is more efficient, sometimes event notifications are more efficient. I generally prefer *not* to poll, but sometimes larger architectural decisions negate the possibility of using notifications. In which case, the only option is to poll. One thing about polling, it is usually best to make the poll interval configurable b/c there is no such thing as the One True Poll Interval.

Christopher 2009-08-20 18:30:18

Well thanks again Christopher you have been a big help. Thanks too for the tip about making it configurable, that is a good idea. Also if anyone else is reading this in the future for tips I also made it to where the loop will break after 25 minutes of trying. I did this because there is the chance that someone would start a build and then interrupt it, so not text file would ever output. Then if I ran this script it would be in a continuous loop. Grant-

cozmokramer8 2009-08-20 19:40:10

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Python question regarding a server listener

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