If you have ever worked on a massively high trafficked website, you know that cache is very important to keeping the server count down and being a superhero to your database servers. Cache can be bad and overly optimized but when you hit a certain threshold, relational databases, databases that are dimension modelled for data warehouse, and even server resources get exhausted. At that point you have two options, buy more servers, or more likely, cache read data.
Each platform has their own way to do this, but there is a common baseplane way to do caching, yes even in .NET. That is with memcached. Memcached is a very common and useful tool that makes caching data and cache layers in an application something that can be the same on every platform. The benefit of using memcached is it is open, common and it has APIs for nearly every popular web development platform (and can be wired in easily to platforms that don’t have their own cache mechanism). Why write your caching layer specific to a certain platform when you can memcache?
If you write high performance web apps and don’t memcache, I feel bad for your server budget and your late nights when that ad buy hits or something popular on your site becomes all the rave.
Perl API
An object-oriented Perl module can be found on CPAN as Cache::Memcached or in Subversion (ChangeLog). (GPL/Artistic)
The Perl API takes advantage of the server’s opaque flag support and sets its “complex” flag whenever the object being stored or retrieved isn’t a plain scalar. In that case, the Storable module is used to freeze and thaw the value automatically going in and out of the memcached.
There is also Cache::Memcached::Fast—another Perl client written in C, largely compatible with the original Cache::Memcached. Available on CPAN at http://search.cpan.org/dist/Cache-Memcached-Fast/.
PHP API
There are tons of PHP libraries available, in different conditions. But it now seems there’s an official one:
Python API
The Python client we’d previously released was just a prototype, and we don’t have regular Python programmers on hand. The folks at Tummy.com have took over maintenance. See ftp://ftp.tummy.com/pub/python-memcached/ for the latest versions.
Ruby API
Java API
A Java API is maintained by Greg Whalin from Meetup.com. You can find that library here:
An improved Java API maintained by Dustin Sallings is also available. Aggressively optimised, ability to run async, supports binary protocol, etc. See site for details:
C# API
There are multiple C# APIs:
C API
Multiple C libraries for memcached exist:
- apr_memcache by Paul Querna; Apache Software License version 2.0
- libmemcached by Brian Aker; BSD license. This is a new library, under heavy development.
- libmemcache by Sean Chittenden; BSD license. This is the original C library. It is no longer under active development. You should try libmemcached instead.
Postgres API
The pgmemcache project allows you to access memcache servers from Postgresql Stored Procedures and Triggers. More details and downloads are available at:
Chicken Scheme
Lua
MySQL API
The memcache_engine allows memcache to work as a storage engine to MySQL. This means that you can SELECT/UPDATE/INSERTE/DELETE from it as though it is a table in MySQL.
A set of MySQL UDFs (user defined functions) to work with memcached using libmemcached.
Protocol
To write a new client, check out the protocol docs. Be aware that the most important part of the client is the hashing across multiple servers, based on the key, or an optional caller-provided hashing value. Feel free to join the mailing list (or mail me directly) for help, inclusion in Subversion, and/or a link to your client from this site.
The best part, they support all good platforms and even Lua, and wisely they left out VB.NET, no worries, VB.NET’ers will never know. Only kidding…
Finally, memcached is distributed, most cache layers included with platforms listed above are in process and per machine. If you are running your code on a webfarm memcached is the only way to go.
