Python, apache, php , mysql weirdness

Sambojambo · 05-22-2008, 08:07 AM

Sorry about the rather obtuse title to this post but I can't really even describe this bug accurately.

I need to call a python script from php. It requires MySQLdb.

Code:

# pytest.py

print('1')
import MySQLdb
print('2')

PHP Code:



<?php 
# apachetest.php 
 
$cmd = "/usr/local/bin/python2.5 /home/sam/www/pytest.py"; 
 
echo("The cmd :: $cmd \n"); 
echo("Output :: \n"); 
 
system("$cmd");

On my dev box (Ubuntu) it works fine. The strangeness happens on the production server (Redhat). I can run apachetest.php from the command line fine - '1' & '2' are printed. But if I call (http://localhost/apachetest.php ) from a webrowser it fails?

So when the apachetest.php gets called by apache it won't import MySQLdb in the python. '1' gets printed but *not* '2'?

I would have thought that the cmd being executed by system( ) would be completely independent of apache?

Anyway I've hit a brick wall - If anybody can shed any light on this for me, I would be very grateful.

Thanks in advance

TB0ne · 05-22-2008, 08:25 AM

Do you have all the Python stuff loaded, like the modules to let Python talk to MySQL? And is MySQL up and running?

Can you run the python script from the command line, outside of PHP?

Sambojambo · 05-22-2008, 08:42 AM

This is where it gets strange. I do have python-mysqldb installed, so when I run the apachetest.php from the command line as below there are no problems:

Code:

[dengmpo@fm-web-1 public_html]$ php apachetest.php
The cmd :: /usr/local/bin/python2.5 /home/dengmpo/public_html/pytest.py
Output
1
2
[dengmpo@fm-web-1 public_html]$

It's when apachetest.php is called from a web browser (http://productionserver.com/apachetest.php) it only reaches the first print line:

Code:

The cmd :: /usr/local/bin/python2.5 /home/dengmpo/public_html/pytest.py Output 1

Why would the php system( ) function effect the behaviour of python when executed by apache?

Sambojambo · 05-22-2008, 08:55 AM

Just a bit of extra info - php is running with SAFE_MODE off and both files are -rwxrwxrwx ...

jiml8 · 05-22-2008, 09:01 AM

Sounds to me like a permissions problem. On your production server, the user apache doesn't have rights to read mySQLdb. Anything run with the system() command runs as user apache so your python script fails.

Either that or there is a path issue and mySQLdb is not being found.

Sambojambo · 05-22-2008, 09:31 AM

Whoa - Dan the man who I work with cracked it. But when you know what to google for it's easy to find the answer - the problem was the same as this post which explains it more clearly than I'd be able to:
http://forum.webfaction.com/viewtopic.php?pid=2152

Solution:

Code:

import os
os.environ['PYTHON_EGG_CACHE'] = '/usr/local/lib/python2.5/eggs'

That was two days of head banging... It wasn't able to write the cache files.

Thanks for you help guys - I can now get three months of development up and running on the production server before the weekend.

smal · 05-22-2008, 09:33 AM

I think - problem may be with SELinux, which running on default Red Hat Linux.
Try to disable SELinux and try again your script.

jiml8 · 05-22-2008, 12:20 PM

I guess I was right; permissions problem. I thought it was a read permission, when it was a write permission, but c'est la vie.