git_in_60_seconds.txt

Git is an open source, distributed version control system implemented 
as a directed acyclic graph of commit objects pointing to snapshots
of content, with all data saved in it's own custom content addressable
filesystem by the SHA-1 checksum hash of each objects data.  branches 
are simply pointers into this directed graph of commits, identifying
entry points that designate the latest work on that branch, allowing
Git to traverse the pointers, determining a coherent history.  
this makes branching cheap and easy, and merging simple, encouraging 
non-linear development styles and frictionless context switching while 
facilitating distributed development, cryptographic integrity and late 
decision making.  nearly all commands run locally with no network 
latency overhead and it is implemented mainly in C, making it 
incredibly fast and efficient even for very large projects.  There 
are several large open source projects using it, not to mention the 
100,000  open source repositories maintained by the 80,000 developers 
on GitHub alone.  

Chances are if you are using another source control system,
you should learn more about Git and consider switching to it.

So, now that we're all on the same page on Git, I'm going to cover 
GitHub a bit.

What is GitHub?  GitHub is a Git-based source code hosting website 
where anyone can freely and openly host their various projects source 
code; and other users can find them, use them and help improve them.  

A lot of people and companies use us for hosting their private and 
open source projects, and we hope you also do.

This talk is to show you how we have used Erlang to help us manage 
the rapid growth of our community in the numbers of projects and users 
in the last year.

Originally, we used a few webservers running Git commands on a shared 
filesystem over GFS.  Due to the nature of GFS and the high IO needs 
of Git, this began to break down - it would not scale.  We decided to 
move to an RPC system, where we would federate our repositories over 
multiple backend servers and run commands over RPC from any frontend 
system, allowing us to scale either tier independently.  

We used Erlang for that RPC system, and here is Tom to show you how.