Possible patch to cure CGI's not finding data for objects in status.dat

Ethan Galstad egalstad at nagios.org
Tue Aug 11 16:29:33 CEST 2009


Hiren Patel wrote:
> Andreas Ericsson wrote:
>>>>  
>>> I tried a program which I meant to attach to this mail that I deleted 
>>> by mistake as I was composing this mail, that fopen'd a file, wrote a 
>>> character at a time and either fclosed at the end, or fsync'd after 
>>> each character, or sync'd after each character. it wrote 1MB worth of 
>>> characters to the file.
>>>
>> Ahmm... That's not really such a great test, tbh. Try the write throughput
>> with a testing tool for it and then divide the size of the file to be
>> synced with the actual write speed of the disk and you'll get something
>> rather close to the cost of a single fsync call for a particular file.
>>
> 
> ah okay, thanks for the reply, I enjoy reading replies from experienced 
> folk, I learn from them.
> 
>>> not sure how useful this really is to get an idea, but sync is clearly 
>>> to be avoided as you mentioned. what do you guys make of the 
>>> difference between fsync and no fsync in relation to nagios?
>>>
>> fsync() isn't needed when using a sane file system. When using an insane
>> one, there are no guarantees that fsync() works anyway, so why use it?
>>
> 
> it's not needed on a sane filesystem because another process trying to 
> read a file not completely sync'd will still see the latest content?
> agree about the NFS issue, read a little about it's problems, and if 
> fsync isn't going to solve its problems, I see your point about not 
> using it.
> 
> if I'm not mistaken this patch was committed already? was there a reason 
> it was so easily accepted?
> 

Yes, it was already committed. As Andreas suggested, it was because
there is negligible impact of the patch, and its probably a best
practice thing given the way the status data is used by other apps.


- Ethan Galstad

------------------------------------------------------------------------------
Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day 
trial. Simplify your report design, integration and deployment - and focus on 
what you do best, core application coding. Discover what's new with 
Crystal Reports now.  http://p.sf.net/sfu/bobj-july




More information about the Developers mailing list