multiple perlbals

Brad Fitzpatrick brad at
Thu Jan 18 00:08:33 UTC 2007

We do this on LiveJournal (~10 perlbals fronting ~100 apaches...) without

Just set your service's max_backend_uses (which is normally 0, for
unlimited), to like 20-100, and then the Perlbals will give up their
connections periodically and give others chances to connect... eventually
(pretty quickly actually), they'll all balance out and have the same
number of backend connections.

Also keep backend_persist_cache reasonable... no more than your Apache's
MaxClients divided by your number of Perlbals, say.

- Brad

On Wed, 17 Jan 2007, Del Raco wrote:

> Hi,
> To avoid a single point of failure, I have multiple
> perlbals set up as reverse proxies to a bunch of
> apache boxes.
> Is it okay for each of the perlbals to frontend all
> the apaches in the backend?
> If "persist_backend" is enabled, would one perlbal
> starve out the other perlbals?
> Thanks.
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