Architecture for the future

After that EVE-centric post on scalability (thanks to HighScalability.com for linking in, hope it was an interesting read), I figured it was time to return to EVE Metrics and other sites- accVIEW and ISKsense.

In the next week we will be migrating to a new server. It’s in the same datacenter with the same host, is a slightly faster machine but has four times as much RAM (8GB) and an additional 10kRPM hard drive. As part of the migration to the new server we’ll be making some changes to the software architecture running the show.

The main difference is that we’re moving away from Passenger, also known as mod_rails. It has some advantages in low-memory conditions, but we’ve had more trouble than it’s worth, so we’ll be moving back to running application servers manually as daemons. For this we’ll be using the excellent Thin application server. For the sites running PHP on the server (this blog, for example), we’ll be using PHP FPM as we are currently; we’ve had no issues with that. Both of those will be sitting as reverse proxies behind nginx. Nginx has done very well as a web server and it’s very fast, as well as being easy to configure.

There is only one other major change; we’ll be sitting nginx itself behind Varnish, a high performance HTTP cache. This will let us more efficiently leverage HTTP caching in our applications and speed up requests dramatically. Right now we don’t use HTTP caching that much; we’d like to change this, particularly in EVE Metrics’ API so we can let Varnish handle a good portion of the thousands of API calls we get asking for the price of trit or what have you. All in all it’ll mean reduced load on the application cluster, which means we can keep that smaller and lighter, which in turn means more room for the database in memory.

That translates to better performance on the more complex components in the site, ie market pages, your account page, corporate pages, and that better performance means we can build more- we’re waiting for the new capacity before we add asset support, one of the things we’re really looking forward to adding, since it will let us add a whole new level of functionality by giving lots more information to processes like our inferred trade detector and our planned fulfilled orders listings. Plus we’ll be adding asset valuation tools, of course.

The architecture I’ve described above will basically be ‘it’ for now; we have more complication at the application and DB layer (We still use MySQL for a few legacy applications, so we have a tiny MySQL server running). The complication at the app layer mainly consists of things like background processing tools, and for EVE Metrics tasks that are actually executed on a VPS and the results uploaded back to the server (we now do all the major CSV dumps on Makurid’s VPS).

As the guy who ends up fixing all this when it goes wrong, simplicity is always my main priority, but the added complexity of Thin and Varnish should be well worth it in the long run.

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