[Spread-users] Story for sysadmin magazine

[George Schlossnagle]

John David Duncan wrote:

>>Real time priority sceduling is available on linux as well.  There is a
>>perl toolkit for doing so on
>>http://www.omniti.com/~george/mod_log_spread/Scheduler-Linux.tar.gz
>>
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>Yes, I'll mention that.
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>>An example of a mod_perl module to duplicate mod_log_spread
>>functionality might be nice if you have one (and if not, I can
>>contribute a perl implementation to CPAN for reference).
>>
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>There's error_log_spread.pl -- should I mention that?  Or do you have
>something more?
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There's a full implementation of mod_log_spread (eith custom logs and 
transfer logs and such) for mod_perl, so that you can use it as a 
PerlLogHandler.  I'll upload it to CPAN this weekend and let you know 
what the package name is, if you're interested.  The nice thing about 
doing it that way over a internal logging script is

1) you dont have to modify any pages (just your httpd.conf)
2) connections to spread are persistent

That may be out of the intended scope of your article though, not sure.


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>>There are some serious idiosynchrocies when running spread in multicast
>>mode on Linux (i your mcast routes aren't set up correctly, your rings
>>will run severely degraded).  Mentioning that might be nice, and/or
>>mentioning how to set it up in broadcast mode (which avoids those
>>problems).
>>
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>I have never used Spread on linux, but realized after I started writing
>this that multicast is a messy topic and some of the things I learned
>about it five years ago aren't true anymore.  (Except that you shouldn't
>even think about trying to route it -- that part is still true :)
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>Maybe I would do better to put a broadcast address in the sample spread
>config?
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I've had so many issues with the multicast idiosynchrocies that I've 
stopped using multicast mode in all the production apps I touch.  It 
just seems to sensitive to obscure breakages.  Yair or someother cnds 
person may take exception to that, and with an IGMP-snooping switch 
there are definite bandwidth benefits to using multicast, but it does 
seem a bit.... persnickety on many platforms.

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>- JD
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