persist_backend and Apache config

Ask Bjørn Hansen ask at
Tue Apr 1 15:16:56 UTC 2008

On Apr 1, 2008, at 7:22, Bill Moseley wrote:

> Can someone explain this difference between the mod_proxy/mod_perl
> recommendation and the perlbal recommendation?

perlbal will reuse the backend connections for whatever request comes  
next, so the backend process is never going to be "idle" if there are  
requests coming in.

> Second, if persist_backen is recommended, what is the recommended
> keep-alive settings for the Apache backend?

With perlbal the general idea is that you run whatever number of httpd  
processes that'll keep the box busy (with whatever is your first  
constraint, typically CPU).   Set that as MaxServers.

KeepAliveTimeout typically can be nice and high; there are no  
particularly good reasons to shutdown the connections.  Of course the  
difference between say 200 and 2000 is pretty small -- if the  
connection has been idle for that long the server obviously isn't  
getting much work anyway.   I usually use somewhere between 60 and 300.

  - ask

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