Re: [undertow-dev] Undertow and non-blocking File IO

> On Nov 25, 2015, at 3:27 PM, Stuart Douglas <sdouglas(a)redhat.com&gt; wrote: > > > > ----- Original Message ----- >> From: "Andrew Brampton" <me(a)bramp.net&gt; >> To: undertow-dev(a)lists.jboss.org >> Sent: Wednesday, 25 November, 2015 4:13:03 PM >> Subject: [undertow-dev] Undertow and non-blocking File IO >> >> I just started playing with Undertow, but I had a couple of questions about >> the use of non-blocking operations vs using the worker thread pool. >> >> In the ResourceHandler.java it appears to dispatch itself onto a worker >> thread, and then uses blocking file IO to actually read the file. I'm >> curious why a AsynchronousFileChannel wasn't used to read from the file in a >> non-blocking way? This would be in keeping with the non-blocking IO threads. > > This is something we should look at, however this only has an actual benefit on Windows AFAIK. Other platforms use SimpleAsynchronousFileChannelImpl which simply delegates to a thread pool. The major issue that prevents this is that Linux filesystems (in combination with the kernel) can sometimes block in io_submit (e.g. during certain metadata operations). You also have to open a file aligned and in O_DIRECT which Java NIO does not support. If you look at what the glibc impl does, it actually ends up creating a thread pool of its own. > >> >> I wrote a quick HttpHandler that used the AsynchronousFileChannel and it >> worked really well. However, when creating AsynchronousFileChannel you have >> to specify the ExecutorService to be used to schedule the completion handler >> callback on. I was able to use exchange.getIoThread().getWorker(), but I'm >> curious if there is a way to schedule it back on the IO Threads? It just >> seems "purer" keeping everything on a single IO thread per core. > > The IO threads implement Executor not ExecutorService, you could write a wrapper, but if you used it on non Windows platforms you would block the IO thread. > > Stuart > >> >> thanks >> Andrew >> >> _______________________________________________ >> undertow-dev mailing list >> undertow-dev(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/undertow-dev > _______________________________________________ > undertow-dev mailing list > undertow-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/undertow-dev -- Jason T. Greene WildFly Lead / JBoss EAP Platform Architect JBoss, a division of Red Hat