Designing Distributed Systems

Chapter 3. Ambassadors

The previous chapter introduced the sidecar pattern, where one container augments a pre-existing container to add functionality. This chapter introduces the ambassador pattern, where an ambassador container brokers interactions between the application container and the rest of the world. As with other single-node patterns, the two containers are tightly linked in a symbiotic pairing that is scheduled to a single machine. A canonical diagram of this pattern is shown in Figure 3-1.

Figure 3-1. Generic ambassador pattern

The value of the ambassador pattern is twofold. First, as with the other single-node patterns, there is inherent value in building modular, reusable containers. The separation of concerns makes the containers easier to build and maintain. Likewise, the ambassador container can be reused with a number of different application containers. This reuse speeds up application development because the container’s code can be reused in a number of places. Additionally the implementation is both more consistent and of a higher quality because it is built once and used in many different contexts.

The rest of this chapter provides a number of examples of using the ambassador pattern to implement a series of real-world applications.

Using an Ambassador to Shard a Service

Sometimes the data that you want to store in a storage layer becomes too big for a ...