concept cluster in category erlang

This is an excerpt from Manning's book Erlang and OTP in Action. Login to get full access to this book.

Erlang programs, on the other hand, aren’t much affected by this kind of problem. As we explained in section 1.1.2, the way Erlang avoids sharing of data and communicates by copying makes the code immediately suitable for splitting over several machines. The kind of intricate data-sharing dependencies between different parts of the code that you can get when programming with threads in an imperative language occur only rarely in Erlang. If it works on your netbook today, it could be running on a cluster tomorrow.

Figure 8.4. Erlang nodes on the network forming a cluster. Each node in the cluster is connected directly to every other node: the network is fully connected.

A cluster of Erlang nodes can consist of two or more nodes. As a practical limit, you may have a couple of dozen, but probably not hundreds of nodes. This is because the cluster is a fully connected network, and the communication overhead for keeping machines in touch with each other increases quadratically with the number of nodes.