Reviewing source code in Kitura boilerplate

The following diagram illustrates the source code files generated from the last section:

The Package.swift is used in the same way as that in a Vapor project. Your application's name, required package dependencies, and different build targets are configured in this manifest file.

A typical Kitura project is partitioned in a similar fashion as in a Vapor project; an application executable module, a test-executable module, and a core application module with all of your application logics:

1. There is only one Swift file in the helloWorld executable module. It serves as an entry point for your project and does several things: It configures Kitura's Helium logger to be used in this project, creates an App() instance, and calls the instance's run() function. The entry point is implemented in a do-try-catch block to catch any runtime errors in your project. In run(), it first calls the postInit() function, then it will configure a HTTP server and start running a Kitura application instance.

1. The App() class used in the main.swift file's do-try-catch block is defined in Application.swift. Before an instance of App() is being constructed, the initializer function init() will be called. The init() function will in turn call initializeMetrics().
2. The initializeMetrics() function is implemented in Metrics.swift. It creates three metrics monitoring instances: a SwiftMetrics to gather performance metrics, a SwiftMetricsDash to enable a dashboard web page that displays the performance metrics, and a SwiftMetricsPrometheus to allow the performance metrics to be used in application clusters monitoring tool.
3. In the basic template, the postInit() function in main.swift sets up only one endpoint: Health Route, by calling the initializeHealthRoutes(app:) function that is defined in HealthRoutes.swift. initializeHealthRoutes(app:) handles the response to the /health endpoint. Any routes such as this Health Route are initialized after an app instance is created, but before a Kitura server is started.
4. Initialization.swift contains only one struct InitializationError() that is inherited from Error() struct. It gives you a chance to modify error messages when there is an error during initialization.

See Appendix B: Kitura Boilerplate Project, for a more detailed review of the files generated in a Kitura boilerplate project.