Facebook takes some heat from Google and others in the social networking community for being a walled garden, keeping the information users share within its friendly confines close to the vest.
But most of the software infrastructure that supports Facebook activities is in fact open source, free for programmers to adopt, customize and use. Google, Twitter, Yahoo and other Internet companies today also support their platforms with open-source products.
Royal Pingdom took time in June to catalogue Facebook's software infrastructure and noted that the social network is largely a LAMP (Linux, Apache, MySQL and PHP) Website, albeit with some modifications.
Facebook uses Sun Microsystems' open-source database MySQL for persistent storage, Memcached for distributed memory caching between its Web servers and MySQL servers, and distributed storage software Cassandra for inbox search.
Facebook also created and released to open-source HipHop for PHP, a compiler that turns PHP into native code on Facebook's Web servers.
"Not only is Facebook using (and contributing to) open-source software such as Linux, Memcached, MySQL, Hadoop, and many others, it has also made much of its internally developed software available as open source, Royal Pingdom noted, citing HipHop, Cassandra, Thrift and Scribe as well as the Tornado Web server.
Other Internet companies use many of the same open-source tools Facebook employs. For example, Twitter uses Cassandra on its geo and research teams.
Facebook and Twitter also use Hadoop, a map-reduce implementation that makes it possible to perform calculations on massive amounts of data. In fact, Hadoop seems to be used by every Internet company worth its salt, from Google to Amazon and Amazon Web services to Yahoo.
Yahoo is a heavy Hadoop user, burning through more than 100,000 CPUs in 36,000 computers for its Web search and ad platforms. The company contributed to the open-source project last month by releasing Hadoop with Kerberos security and a workflow engine for Hadoop.
Why, after years of enterprises powered by proprietary software infrastructure from Microsoft, Oracle, HP, IBM and others, are big Internet companies writing or adopting open source with such gusto?