Export services via port binding

At times, the server functions as a web server container where the web app operates as a module within the container. For instance, a PHP app might run as a module inside Apache HTTPD, or Java apps might function within Tomcat.

The twelve-factor app is entirely self-contained and doesn't depend on the runtime injection of a web server into the execution environment to establish a web-facing server. Instead, the web app exports HTTP as a service by binding to a port, which serves as a listening port for incoming requests. In a local environment, developers access the app by visiting http://localhost:3000. In a deployment environment, a routing layer manages the routing of requests from a public-facing hostname to the port-bound web processes.

This is commonly achieved by using dependency declarations to incorporate the web server library into the app, such as using Thin for Ruby.

Furthermore, this approach signifies that any service can be exported by port binding, awaiting incoming requests. It's important to note that by doing so, one app can serve as the backing service for another app.

This Twelve-Factor App post series is a means for me to consolidate the knowledge I've gained while studying these rules. Please feel free to visit [the site (https://12factor.net/) for more detailed explanations. That's all folks!