Thanks, I think we're on the same page. I was considering something outside of the Racket web server handling the affinity. For example, the nginx web server / load balancer being responsible to send subsequent requests from a client to the same server process that handled the initial request.
On Jul 17, 2014, at 10:38 AM, Jay McCarthy wrote: > Hi Brian, > > Stateful continuations have to be invoked from the process that > capture them. That's like session affinity. The reason I said it > doesn't make a lot of sense is that continuations don't really have a > "parent" and aren't really in a "session". There's not necessarily a > connection between one continuation and another. > > Jay > > On Thu, Jul 17, 2014 at 10:33 AM, Brian Adkins <racketus...@lojic.com> wrote: >> Jay: >> >> Can you clarify your statement, "Session affinity doesn't really make a lot >> of sense in the continuation context, fwiw." ? >> >> I haven't really dug into the web server yet, so I may simply be >> misunderstanding how it works, but at least in the case of stateful >> continuations, I thought it was important for all of a user's subsequent >> requests to go to the same process that served the first request since there >> would be state stored in the memory of the web server process. >> >> Is that not the case? Or are all continuations serialized to disk so that >> any Racket web server process (assuming there are multiple instances >> running) could serve a subsequent request for any continuation? >> >> To be clear, the scenario I'm envisioning is that of an nginx web server >> handling all incoming http requests, serving static files itself and >> proxying all other requests to a set of Racket web server instances using >> some sort of load balancing such as round robin. I assumed that if I begin >> my session with process-1 and then the next request was served by process-2, >> it would fail. >> >> Thanks, >> Brian >> >> On Jul 16, 2014, at 10:17 PM, Jay McCarthy wrote: >> >>> It wouldn't have a big impact on the server. The big question is how >>> to effectively use multi-core in Racket programs generally. >>> >>> Futures are really only good for numerical codes that stay in the JIT, >>> which doesn't sound like most Web programs. That said, it is trivial >>> to implement: >>> >>> #lang racket/base >>> (require racket/future >>> web-server/servlet-env >>> web-server/http) >>> >>> (define (fib n) >>> (if (< n 2) >>> 1 >>> (+ (fib (- n 1)) >>> (fib (- n 2))))) >>> >>> (define (start req) >>> (touch >>> (future >>> (λ () >>> (response/xexpr >>> `(html >>> (body >>> (p "It's " >>> ,(number->string >>> (fib (random 20))))))))))) >>> >>> (serve/servlet start) >>> >>> Boom! That's a servlet that uses multi-core to handle every request... >>> of course, it probably doesn't pay in this or most other programs. >>> >>> Places are for more coarse-grained things and you can pass file >>> descriptors, so it's feasible to have a TCP accepter that feeds work >>> to a group of places servicing the requests. However, places must not >>> use mutation to communicate higher-order values (they can communicate >>> flat values like numbers with mutation), so they couldn't share >>> continuations. It would be trivial to use serializable continuations >>> or to implement a continuation manager that stored all the >>> continuations in a single place. Session affinity doesn't really make >>> a lot of sense in the continuation context, fwiw. >>> >>> My guess is that you could spend less than 100 lines to implement the >>> continuation manager and the place-based worker setup. (This is based >>> on the normal server setup just being 127 lines and the manager >>> interface being implemented in as little as 40 lines.) This might be >>> worth it. >>> >>> Jay >>> >>> >>> On Wed, Jul 16, 2014 at 4:09 PM, Brian Adkins <racketus...@lojic.com> wrote: >>>> I haven't looked into the Racket web server much yet, so I'd like to >>>> understand the implications of this. >>>> >>>> My experience is with stateless http app servers (primarily with Unicorn >>>> Ruby servers at the moment), so firing up a number of worker processes and >>>> having something like nginx proxy to them works well to fully utilize all >>>> cores. >>>> >>>> I think I read that the Racket web server makes use of continuations, so I >>>> expect some sort of process affinity would be necessary, where a given >>>> user's requests are always proxied to the same worker process - is that >>>> right? Is it common to use multiple web server processes in Racket web >>>> apps? >>>> >>>> In your estimation, what is the feasibility of adding multi-core support >>>> to the Racket web server? For example, is it reasonably feasible and on >>>> the current roadmap, or would it require massive changes to the web server? >>>> >>>> Thanks, >>>> Brian >>>> >>>> On Jul 16, 2014, at 8:42 AM, Jay McCarthy wrote: >>>> >>>>> It does not use multiple cores if they are available. >>>>> >>>>> Jay >>>>> >>>>> On Wed, Jul 16, 2014 at 7:02 AM, Sean Kemplay <sean.kemp...@gmail.com> >>>>> wrote: >>>>>> Hello, >>>>>> >>>>>> I am interested in the racket web server for some micro services. Just >>>>>> wondering if by default it runs across multiple cores or if it is >>>>>> restricted >>>>>> to one due to threads in racket. >>>>>> >>>>>> Regards, >>>>>> Sean >>>>>> >>>>>> >>>>>> ____________________ >>>>>> Racket Users list: >>>>>> http://lists.racket-lang.org/users >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Jay McCarthy >>>>> http://jeapostrophe.github.io >>>>> >>>>> "Wherefore, be not weary in well-doing, >>>>> for ye are laying the foundation of a great work. >>>>> And out of small things proceedeth that which is great." >>>>> - D&C 64:33 >>>>> ____________________ >>>>> Racket Users list: >>>>> http://lists.racket-lang.org/users >>>> >>> >>> >>> >>> -- >>> Jay McCarthy >>> http://jeapostrophe.github.io >>> >>> "Wherefore, be not weary in well-doing, >>> for ye are laying the foundation of a great work. >>> And out of small things proceedeth that which is great." >>> - D&C 64:33 >> > > > > -- > Jay McCarthy > http://jeapostrophe.github.io > > "Wherefore, be not weary in well-doing, > for ye are laying the foundation of a great work. > And out of small things proceedeth that which is great." > - D&C 64:33 ____________________ Racket Users list: http://lists.racket-lang.org/users
