ZeroMQ

Reliable Publish-Subscribe (Clone Pattern)

As a larger worked example, we’ll take the problem of making a reliable publish-subscribe architecture. We’ll develop this in stages. The goal is to allow a set of applications to share some common state. Here are our technical challenges:

• We have a large set of client applications—say, thousands or tens of thousands.

• They will join and leave the network arbitrarily.

• These applications must share a single, eventually consistent state.

• Any application can update the state at any point in time.

Let’s say that updates are reasonably low-volume, we don’t have real time goals, and the whole state can fit into memory. Some plausible use cases are:

• A configuration that is shared by a group of cloud servers

• Some game state shared by a group of players

• Exchange rate data that is updated in real time and available to applications