Re: how to do cloud computing with php

On 24 Mar 2010, at 11:55, Rene Veerman wrote: > As a way to take a few steps back from the kinda heated "when will php > grow up and support threading" thread, i'm requesting you people list > how you scale from 1 server to many servers; what's called cloud > computing. > > In particular, i'm interested in how to set up an application that > deals with great amounts of input from many 3rd-party servers, and say > a million concurrent viewers who need html calculated from those input > streams. > > So this goes beyond 1 mysql server, and beyond 1 php server. > > Let's hear it, coz quite frankly i have my doubts about php's ability > to scale to cloud computing. The way you're using the term cloud computing differs from the generally accepted definition, which is "delivering hosted services over the Internet". What you're talking about is scaling an application beyond a single server which is a different, albeit usually related, beast. There is no single or "right" way to implement a scalable web application but there are some key principles. The main principle that enables maintainable scalable systems is layers. If you build your application in a layered fashion, such that no layer knows how the other layers work, you can modify any of the layers in any way you need to when scalability issues arise. Your hardware setup will depend on the application and usage patterns, but some combination of load balancers, application servers and database servers is pretty normal. You may also find servers dedicated to caching and offline processing useful to achieve your goals. Architecture-wise you'll want to make extensive use of caching to lighten the load on the database, and you'll want to make sure that you perform no processing during a request that could wait to be processed offline. The main site I maintain has two load balancers at the front running nginx, three application servers running FastCGI PHP processes, two database servers in a master/slave arrangement, a separate static server and two offline processing servers. The application servers all have memcached instances for caching purposes and each runs its own instance of Sphinx to localise the search load. That setup, combined with a shared-nothing approach to the application design means I have a highly scalable system. To add capacity I simple need to add servers in whichever group is having issues. Due to the nature of the application I'm yet to come close to having issues with the number of concurrent writes to the database, but when I do I already plan to add another master server such that I have a master/master/slave setup. Unless you do start getting the sort of traffic that Facebook are blessed with you will be able to get a long way with this type of arrangement. And with a modular, layered approach to the application design I don't see any reason why I can't handle any scalability issue that's likely to come along with a minimum of fuss and cost. The key think to remember is that scalability is not the same as performance. They're barely even related. What, specifically, makes you doubt PHP's ability to scale? -Stuart -- http://stut.net/