On 10/23/07, Robert Mela <[EMAIL PROTECTED]> wrote: > > Several years back I accidentally discovered that multiple processes can > listen on the same TCP/IP socket. The trick of course is that all the > processes are in the same process group, and the socket is opened by a > shared parent. The OS somehow was managing queuing up the various > calls to accept() on that socket. Since the watchdog parent / multiple > child servers is a common, this was a workable solution on the versions > of Linux we were using. > > IIRC, the OS gracefully queued several processes' calls to accept(), > requiring no additional synchronization. But, even if that weren't the > case, there is still the option of puting an acceptor in a parent and > dispatching the client socket to available child servers. > > Anyhow -- > > The application I wrote has a watchdog process in C that opens up a > server socket before forking child server processes. The children get > passed the descriptor number for that server socket as an argument on > their command lines. > > All child server processes then enter an accept loop. They all call > accept() on that same, shared descriptor . Each child, btw, opened up > its own "private" admin socket on a port that was an offset of the main, > shared service port ( and optionally on a different interface as well ). > > Within a pool then processes are somewhat self-balancing -- a process > only calls accept() when it's got threads available and ready to handle > a reqeust. Clients, or a client load balancer, don't have to keep > track of traffic or request counts between individual server processes. > They also don't have to try back-end app servers individually before > finding a "thread" that's free -- if any process in a pool is > available, it's already sitting in accept() on that shared socket ( > likely with others queued up behind it in their accept() calls). > > If Mongrel's suitable as an Internet-facing front-end, then there might > be, for many applications, no need for a load balancing proxy. Simply > fire up a pool of mongrels at port 80, and they'll sort it all out among > themselves. Even for applications requiring multiple machines a scheme > like this would simplify load balancer proxy configurations (100 > mongrels in a pool? No problem -- all one port!) > > I'm sure the folks who wrote Mongrel thought of this and either tried it > or rejected it beforehand for good reason. And I had the luxury of > coding for just one platform. Perhaps others impose hurdles that make > this impractical. But even there, isn't there the Apache model of a > parent acceptor() passing client sockets to ready children? > > > Thoughts? >
I believe that the main issue here is on the win32 platform, Luis? We do have something similar in the works for a future release, however I am unsure as to how your suggestion ties in at the moment. It appears to be well worth investigation for what we have planned. Thank you kindly for this, ~Wayne
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