" You should take care to not overload your backend servers in the first place "
Yes, that is what we are trying to achieve using autoscaling of the backend servers :) I would have like to use the maxconns against backend but we did not have time to tune this before the release. "Generally, I think you should make sure that your service is not getting overwhelmed by starting new instances earlier" We are actually scaling very aggressive plus that we have a lot of instances running. So we are using more of a "scaling down" concept currently. But you never know, big releases going mainstream tends to generate traffic so we need to make sure that scaling further up will work as expected. /E -----Original Message----- From: Holger Just [mailto:hapr...@meine-er.de] Sent: den 7 november 2011 12:45 To: haproxy@formilux.org Subject: Re: Autoscaling in haproxy with persistence sessions On 2011-11-07 21:32, Erik Torlen wrote: > If you get a burst against 3 active backend servers they will take > care of all the request and connections. The clients that are active > will then get a persistence sessions against 1 of these 3 servers. It > will take ~5min to scale up a new server so during that period more > clients could come in and the 3 backend would then be even more > overloaded. You should take care to not overload your backend servers in the first place. The connection limits can be finely tunes your each backend server. Requests exceeding the limits are queued which will prevent your servers from getting overwhelmed and dieing, usually taking others with it. Generally, I think you should make sure that your service is not getting overwhelmed by starting new instances earlier so you can actually handle the traffic. But in the end, I think it depends on how important session locality is for your service, i.e. which of those you can accept earlier: broken session locality or slightly delayed responsed due to queing. --Holger
