[mod_python] modpython, mysqldb best paractice

Martijn Moeling martijn at xs4us.nu
Wed Dec 17 08:28:53 EST 2008


Your right about req.connection, On my behalf a big sorry, since my  
new macbook pro made me answer an old question ("Date received" Column  
was sorted upside down)


On Dec 16, 2008, at 9:53 PM, Graham Dumpleton wrote:

> 2008/12/17 Martijn Moeling <martijn at xs4us.nu>:
>> Hi,
>> I am running stable on a production machine (uptime > 1 year) on a  
>> 6000
>> hits/week system:
>> (CentOs 64 bit)
>> I solved problems with hanging connections (cousing "memory leaks")
>> some hints and tips:
>> Never ever connect to mysql globally but connect to mysql in you  
>> handler
>> stage
>> Not even consider connection pools, mysql is fast enough.
>> make the connection a part of the request object so you can pass  
>> the request
>> object around
>> so req.connection and req.cursor exist.
> Don't save it as req.connection, that attribute is a reference to the
> Apache connection object for the HTTP request. Call them
> 'dbconnection' and 'dbcursor' to avoid conflicts.
> Graham
>> right after you make the connection do a req.register_cleanup to a  
>> function
>> similair to:
>> def closedb(req):
>>       req.cusor.close()
>>       req.connection.close()
>> Now when users stop the downloading (by pressing the stop button)or  
>> when a
>> python error occurs the connection is closed too. Otherwise mysql  
>> will keep
>> the connection and runs out after a while (for me this happenend at  
>> around
>> 19000 request but that depends on system configuration and  
>> installed memory.
>> Off topic: when I started using SQLAlchemy i had to find a way to  
>> to this
>> (since sqlAlchemy is using mysqldb) because this problem started to  
>> come
>> back.
>> I have found a way around it by using a "hidden" feature of  
>> SQLAlchemy, If
>> people are interested please let me know, i'll post it.
>> Martijn
>> On Jul 19, 2006, at 11:04 PM, Deron Meranda wrote:
>>> On 7/19/06, Jim Gallacher <jpg at jgassociates.ca> wrote:
>>>> CentOS kernel issues resulting in similar problem (but not just  
>>>> mysql):
>>>> http://bugs.centos.org/view.php?id=1174
>>> Ah, I did not know about that one.  From reading it, this sounds
>>> almost exactly like the problem Martijn is probably experiencing.
>>> I doubt mod_python memory leaks would exhibit the same type
>>> of behavior Martijn describes.  This is why I suggested
>>> monitoring with vmstat...if this is the problem it should show up
>>> quite obviously.  (Of course I don't know what kernel Martijn
>>> is running at this point in the thread)
>>> BTW, I'm also running everything under CentOS 4 as well
>>> (with the 2.6.9-34.0.1.ELsmp kernel), but have not seen any
>>> problems at all.  But then I'm in IA32, and not IA64, which is
>>> what this bug report as well as Martjin are running.  So it looks
>>> like a possible bad Linux kernel for 64-bit.
>>> Martijn, can you provide your kernel version, etc.?
>>> Good news is that a new fixed kernel is apparently on the way.
>>> --
>>> Deron Meranda
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