Dependencies

Servers

In a simple environment, these can all be run on one machine. For a larger site, they will almost certainly need to be split out to different hosts.

Dependency	Version	Ubuntu Package(s)	Description
PostgreSQL	9.0+	postgresql	Robust RDBMS. Used as primary data store.
Cassandra	1.0+	cassandra in ppa:reddit	Distributed database. Slowly becoming primary data store.
memcached	1.4+	memcached	Fast in-memory caching server. Used throughout reddit.
RabbitMQ	2.0+	rabbitmq-server	AMQP server. Used for offline processing.
HAProxy		haproxy	Load balancer for distributing requests to app servers.
stunnel	patched	stunnel	For HTTPS support. Needs to be a version with the X-Forwarded-For patches on top. (see ppa:reddit.

Libraries

The following libraries are prerequisites before an install can begin. With these requirements satisfied, setup.py should be able to take care of the remaining python dependencies.

Dependency	Version	Ubuntu Package(s)	Description
Python	2.7.x	python-dev	Headers for building python modules.
libmemcached	0.32+	libmemcached-dev	For communication with memcached.
libpq		libpq-dev	C library for PostgreSQL.
libxml2		libxml2-dev	XML Parsing Library (for python's lxml)
libxslt1		libxslt1-dev	XSLT library (for python's lxml)
PIL		python-imaging	This is not strictly necessary as setup.py will install it. However, a PyPI-installed copy of PIL will not work out of the box on a Debian/Ubuntu install because it will have trouble finding the C libraries for JPEG / PNG etc.

Misc. Utilities

Dependency	Version	Ubuntu Package(s)	Description
Git		git-core	reddit code is stored in Git.
GCC		gcc	Used for compiling python modules etc.
optipng		optipng	Used to compress auto-generated CSS spritemap and thumbnails.
jpegoptim		jpegoptim	Used to compress thumbnails.
psql		postgresql-client	CLI client for managing PostgreSQL. Used by some processing jobs.
make		make	Build tool.
gettext		gettext	Tools for internationalization.
node.js		nodejs	Javascript environment.
less.js		node-less	CSS Precompiler.