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Java Forum / General / August 2007mutithreading in webapps
hi all, i was trying to implement a design which is like dispatcher, worker model where N number of requests come in, which are queued for the dispatcher to pick them up and spawn a worker thread to process each of these requests. of course we will use thread pool for worker threads. but i was told that issues might occur with multi threading in webapp. i am using Tomcat container. is it not advisable to go for such multi threaded designs in webapps / tomcat ? one reason could be since webapps typically run for longeeeeeerrrr period of time than usual desktop apps so the chances of memory leaks or inappropriate resource handling might affect adversely in webapps with muti-threaded design. has anyone experienced such problems with threads in tomcat ? thanks amey > i was trying to implement a design which is like dispatcher, worker > model where N number of requests come in, which are queued for the [quoted text clipped - 10 lines] > > has anyone experienced such problems with threads in tomcat ? Servlet containers are intended for: - web request comes in - web response go back out They are not intended for long time number crunching or such. The container uses threading itself to serve multiple requests in parallel. It is legal according to the spec to start multiple threads, so you could: - web request comes in - you start N threads - you wait to all threads are done - web response go back out But if it takes a long time, the the browser will consider it a timeout. So it is not a problem whether multi threading will work in Tomcat - it is a question whether it is a good way of solving the problem. Arne On Aug 5, 6:58 am, Arne Vajh?j <a...@vajhoej.dk> wrote: > > i was trying to implement a design which is like dispatcher, worker > > model where N number of requests come in, which are queued for the [quoted text clipped - 34 lines] > > Arne It is doable (and we've done it where I work). Although, you might consider having a separate standalone process (in a different JVM) handle the actual work. > It is doable (and we've done it where I work). Although, you might > consider having a separate standalone process (in a different JVM) > handle the actual work.- Hi Daniel, any specific reason that you can mention for running it in different JVM? do you think it might make the core webapp unstable ? i am actually writing a notification service where ppl will post request to the service which will notify to the intended recepients (by mails or other means) thanks. amey >> So it is not a problem whether multi threading will work in Tomcat - it >> is a question whether it is a good way of solving the problem. > > It is doable (and we've done it where I work). Although, you might > consider having a separate standalone process (in a different JVM) > handle the actual work. I know it is doable. But it is not the usage servlet containers were designed for. Arne > It is legal according to the spec to start multiple threads, so > you could: [quoted text clipped - 10 lines] > > Arne well my web request will not be waiting till the job is done. it is actually a notification service, ppl will keep posting it and then it will pick up all queued requests and notify the recepients (say by mail or other means) so the web response is not blocked on the completion of the worker thread. amey >> It is legal according to the spec to start multiple threads, so >> you could: [quoted text clipped - 15 lines] > so the web response is not blocked on the completion of the worker > thread. If you could upgrade from a servlet container (Tomcat) to a full J2EE application server (like JBoss with Tomcat embedded as servlet container), then you could: - web request comes in - servlet queue task to message queue - web response go back out - a message driven bean process the input from the message queue Your solution will also work, but I believe the above is "the J2EE way". Arne >> It is legal according to the spec to start multiple threads, so >> you could: [quoted text clipped - 17 lines] > so the web response is not blocked on the completion of the worker > thread. This can be made to work inside Tomca, but there are subtle isses. 1. You need to make your background threads daemon threads, or normal Tomcat shutdown won't work, because even after all messages are done processing, your threads will still be active. 2. If your application is stopped using Tomcat's mangement interface, your background threads should stop too. You need to hook the Servelet.destroy() method to accomplish this. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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