Re: modproxy load balancer

Graham Leggett wrote:

> Theo E. Schlossnagle wrote:
>
>> I am not sure how you invision the hooks being loaded at runtime.  If 
>> they are their own modules, and just place themselves in the 
>> mod_proxy chain, then I can piggyback on the the builtin module 
>> inititalization functions.  Otherwise, I need someway to initialize 
>> my module.
>
>
> Use the exact same model as is used now for proxy_http, proxy_ftp and 
> proxy_connect. All three of these modules depend on hooks defined 
> inside mod_proxy.
>
> mod_dns, mod_sticky, mod_backhand, etc would simply be the 4th, 5th 
> and 6th module dependant on mod_proxy.
>
>> I don't think the hook should be responsible for making the 
>> connection.  I think the hook should be solely responsible for 
>> listing, in order of preference, where connections should be 
>> established.  In perl syntax:
>>
>> [
>>   { 'protocol' => 'http',
>>     'IP' => '10.2.3.4',
>>     'port' => '80' },
>>   { 'protocol' => 'http',
>>     'IP' => '10.2.3.8',
>>     'port' => '8080' },
>> ]
>>
>> then mod_proxy should be responsible for taking that list and making 
>> real and usable connections out of them.
>
>
> Ok... my thinking was that it would simplify the notification to the 
> backend of connection success or failure, but then doing it your way 
> simplifies the backend module.
>
> What we could do is have two hooks - the first gets given an 
> URL/hostname/port, and returns a list of IPs to try.
>
> Proxy then tries those IPs in turn.
>
> Then a second hook is run saying "oh by the way, that IP address you 
> gave me is down with status whatever, or it worked fine thanks".
>
> If a connection failed, all the backend modules get to find out and 
> can blacklist that server, whatever. If the connection succeeded, the 
> time difference between the first and second hook would be the total 
> time of connection, which could be used for loading stats. 

Yes, this is exactly what I was thinking.  Thanks for explaining your 
reason for making the hook do the connection.

Bill