The sidecar pattern can be used for more than adaptation and monitoring. It can also be used as a means to implement the complete logic for your application in a simplified, modular manner. As an example, imagine building a simple platform as a service (PaaS) built around the git workflow. Once you deploy this PaaS, simply pushing new code up to a Git repository results in that code being deployed to the running servers. We’ll see how the sidecar pattern makes building this PaaS remarkably straightforward.

As previously stated, in the sidecar pattern there are two containers: the main application container and the sidecar. In our simple PaaS application, the main container is a Node.js server that implements a web server. The Node.js server is instrumented so that it automatically reloads the server when new files are updated. This is accomplished with the nodemon tool.