Alexey Verkhovsky wrote:
On 10/15/07, Zed A. Shaw <[EMAIL PROTECTED]> wrote:
Tried Lucas Carlson's Dr. Proxy yet? Other solutions? Evented mongrel?
HAProxy (and some other proxies smarter than mod_proxy_balancer)
solves this problem by allowing to set the maximum number of requests
outstanding to any node in the cluster.
But m_p_b is correct in this!!! It's the "max" attribute to BalancerMember.
It's just a pain to discover the correct combination of parameters!
Setting it to 1 means that it
will only ask a Mongrel instance to serve a request when it's not
already doing so
But mpb IS doing this correctly, as you specify! It's a matter of
combining "max" and "acquire" attrs on BalancerMember. Perhaps the
thing that needs changing is documentation, making this the default mpb
behavior, or better documentation ( or all of the above! )
. Which makes perfect sense with Rails
(single-threaded), especially if you do have something else to serve
static content in this setup.
Setting num_processors to 1 is only possible when you have a proxy
that can restrict itself from sending more than one request per
Mongrel.
Which we do in m_p_b, via the "max" attribute to BalancerMember
Otherwise, if I remember correctly, you replace occasional
delays with HTTP 503s. Not a good trade-off.
The 503s would only be generated in the case of incorrect mpb
settings. A 503 "server busy" coming from the Mongrel back-end gives
developers and admins a better idea of what's really happening.
Consider: the back end has reached maximum capacity. Saying "Hey
503! I'm at max capacity" is better than the current action -- open and
close with no indication of what's wrong.
Setting num_processors low has a positive side effect of restricting
how far your Mongrel will grow in memory when put under strain even
5), just so that monitoring can hit it at the same time when load
balancer does.
Excellent idea!
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fn:Robert Mela
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