Hi! I've been using Mongrel in a Rails setup with HAProxy as a loadbalancer. I used to use Pound, but HAProxy is much more performant and has the very nice option to limit the amount of requests sent to the backend servers/processes. In practice, this means that a new incoming request will not be sent to a Mongrel that's already busy processing a request. There's an exception to this wonderful world though. If a request takes a long time to finish, either HAProxy can timeout, or the user presses the 'stop' button or does a reload. This means that there's no way the result of whatever that Rails process is doing at that time will make it back to the user. Also, in this case HAProxy thinks the backend server is ready to accept a new connection, which will only get queued up a Mongrel level, causing yet another user to wait for ages or do a stop/reload, leading to a possibe escalation of long running processes and users waiting for responses. Wouldn't it be possible to have an option where you kill the current running thread (Rails process) when a new one gets accepted ? I believe that's what the -n option was meant to do, still, this doesn't seem to work 100% the way I'd except it to (which means nothing). In my experiments, the long running request just continues until it's finished. Alternatively if mongrel wouldn't accept new requests when it's still busy processing one, and the loadbalancer (HAProxy) would detect it can't connect and try the next server, this would be a smaller step in the right direction (I think). I know you should just avoid long-running processes and let backgroundrb handle them, which I do in several cases, but on one installation there's so much data in the (oracle) database which is continuously growing that if it decides to take an alternative path to resolving a query this can have a disastrous impact on performance. These are just my ideas, if anyone has a better solution or suggestions, I'd really like to hear about them. Piet.
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