Erlang Interview

André Pang was interviewed at builder.au re: Erlang...

Our very first server was written in C++, but we realised that we had a problem if the server crashes. There might be 20 VFX houses connected to this server, and when it goes down, they all go down with it. So we looked at using an Erlang server, by writing custom plug-ins to ejabberd, which is a popular XMPP (Extensible Messaging and Presence Protocol) platform -- so we layered all of our code above that.

In the end we found that to be a good solution, in fact the only time I can remember it crashing is when we forgot to allocate swap space for the server and it ran out of memory. Due to the way you can set up ejabberd and Erlang in general is that it really suits a distributed system without a single point of failure. It makes it easy to set up different nodes which all replicate as each other, for instance, there were plenty of times when the primary server went down, but users were automatically connected to the secondary server instead. With a bit of smarts in the client it was possible to reconnect to a secondary server in the middle of the session and only lose a small amount of information in the process.

We had three or four servers around the world, and it was incredibly cheap to deploy, because with the Erlang runtime you don't need any special hardware or anything. It was very reliable and turned out to be a very good decision.