has anybody used ->http://commons.apache.org/daemon/ ??
On 3/9/08, Steve Loughran <[EMAIL PROTECTED]> wrote: > > On Sun, Mar 9, 2008 at 2:36 PM, John D. Mitchell <[EMAIL PROTECTED]> > wrote: > > On Sat, Mar 8, 2008 at 2:29 PM, Steve Loughran <[EMAIL PROTECTED]> > wrote: > > [...] > > > > > you're server should start returning something other than 200 from > its > > > happy page, and the HTTP-aware front end load balancer (which polls > > > these pages) will stop routing traffic to it. That makes it implicit > > > that new work doesn't come in. It also stops this box receiving work > > > when it is unhappy for other reasons, like it can't talk to the > > > database or there's no temp file storage. > > > > Indeed. [Of course, then you have to deal with the failure modes for > > the load balancers themselves, heartbeat bugs, what happens when all > > of the back-end servers fail, etc.. :-)] > > > There's always a single point of failure, it just moves around the > system... > > > > Just to be clear, what Steve is talking about is that a decent > > load-balancer setup will have the load-balancer regularly (e.g., 1 / > > second) ping each of the underlying load-balanced services at an "I'm > > alive" URL (a so-called heartbeat check). If the load balancer > > receives anything other than an HTTP 200 response (or cannot even > > connect at all) then it assumes the server is down and should be taken > > out of the active pool. > > > > > Exactly, And for those load balancers to do their work right, you had > better have that status page recognise when things are wrong. > Otherwise requests get routed their way only to fail shortly > afterwards. More amusingly, if the back ends fail really rapidly > -because they arent doing useful work- the router actually sends more > work that way, because its workload queue is shorter. > > > -steve >
