Improving the network scalability of Erlang

As the number of cores grows in commodity architectures so does the like- lihood of failures. A distributed actor model potentially facilitates the de- velopment of reliable and scalable software on these architectures. Key com- ponents include lightweight processes which ‘share nothing’ and hence can fail independently. Erlang is not only increasingly widely used, but the un- derlying actor model has been a beacon for programming language design, influencing for example Scala, Clojure and Cloud Haskell.

While the Erlang distributed actor model is inherently scalable, we demon- strate that it is limited by some pragmatic factors. We address two network scalability issues here: globally registered process names must be updated on every node (virtual machine) in the system, and any Erlang nodes that com- municate maintain an active connection. That is, there is a fully connected O(n^2) network of n nodes.

We present the design, implementation, and initial evaluation of a con- servative extension of Erlang – Scalable Distributed (SD) Erlang. SD Erlang partitions the global namespace and connection network using s groups. An s group is a set of nodes with its own process namespace and with a fully connected network within the s group, but only individual connections out- side it. As a node may belong to more than one s group it is possible to construct arbitrary connection topologies like trees or rings.