Designing Distributed Systems, 2nd Edition

Chapter 5. Adapters

In the preceding chapters, we saw how the sidecar pattern can extend and augment existing application containers. We also saw how ambassadors can alter and broker how an application container communicates with the external world. This chapter describes the final single-node pattern: the adapter pattern. In the adapter pattern, the adapter container is used to modify the interface of the application container so that it conforms to some predefined interface that is expected of all applications. For example, an adapter might ensure that an application implements a consistent monitoring interface. Or it might ensure that log files are always written to stdout or any number of other conventions.

Real-world application development is a heterogeneous, hybrid exercise. Some parts of your application might be written from scratch by your team, some supplied by vendors, and some might consist entirely of off-the-shelf open source or proprietary software that you consume as precompiled binary. The net effect of this heterogeneity is that any real-world application you deploy will have been written in a variety of languages, with a variety of conventions for logging, monitoring, and other common services.

Yet, to effectively monitor and operate your application, you need common interfaces. When each application provides metrics using a different format and interface, it is very difficult to collect all of those metrics in a single place for visualization and alerting. ...