Chapter 10. Overriding Core Backend Service Configuration The Red Hat Developer Hub (RHDH) backend platform consists of a number of core services that are well encapsulated. The RHDH backend installs these default core services statically during initialization. You can configure these core services by customizing the backend source code and rebuilding your Developer Hub application. Alternatively, you can customize a core service by installing it as a BackendFeature by using dynamic plugin functionality. To use the dynamic plugin functionality to customize a core service in your RHDH application, you must configure the backend to avoid statically installing a given default core service. For example, adding a middleware function to handle all incoming requests can be done by installing a custom configure function for the root HTTP router backend service which allows access to the underlying Express application. Example of a BackendFeature middleware function to handle incoming HTTP requests // Create the BackendFeature export const customRootHttpServerFactory: BackendFeature = rootHttpRouterServiceFactory({ configure: ({ app, routes, middleware, logger }) => { logger.info( 'Using custom root HttpRouterServiceFactory configure function', ); app.use(middleware.helmet()); app.use(middleware.cors()); app.use(middleware.compression()); app.use(middleware.logging()); // Add a the custom middleware function before all // of the route handlers app.use(addTestHeaderMiddleware({ logger })); app.use(routes); app.use(middleware.notFound()); app.use(middleware.error()); }, }); // Export the BackendFeature as the default entrypoint export default customRootHttpServerFactory; In the above example, as the BackendFeature overrides the default implementation of the HTTP router service, you must set the ENABLE_CORE_ROOTHTTPROUTER_OVERRIDE environment variable to true so that the Developer Hub does not install the default implementation automatically. 10.1. Overriding environment variables To allow a dynamic plugin to load a core service override, you must start the Developer Hub backend with the corresponding core service ID environment variable set to true . Table 10.1. Environment variables and core service IDs Variable Description ENABLE_CORE_AUTH_OVERRIDE Override the core.auth service ENABLE_CORE_CACHE_OVERRIDE Override the core.cache service ENABLE_CORE_ROOTCONFIG_OVERRIDE Override the core.rootConfig service ENABLE_CORE_DATABASE_OVERRIDE Override the core.database service ENABLE_CORE_DISCOVERY_OVERRIDE Override the core.discovery service ENABLE_CORE_HTTPAUTH_OVERRIDE Override the core.httpAuth service ENABLE_CORE_HTTPROUTER_OVERRIDE Override the core.httpRouter service ENABLE_CORE_LIFECYCLE_OVERRIDE Override the core.lifecycle service ENABLE_CORE_LOGGER_OVERRIDE Override the core.logger service ENABLE_CORE_PERMISSIONS_OVERRIDE Override the core.permissions service ENABLE_CORE_ROOTHEALTH_OVERRIDE Override the core.rootHealth service ENABLE_CORE_ROOTHTTPROUTER_OVERRIDE Override the core.rootHttpRouter service ENABLE_CORE_ROOTLIFECYCLE_OVERRIDE Override the core.rootLifecycle service ENABLE_CORE_SCHEDULER_OVERRIDE Override the core.scheduler service ENABLE_CORE_USERINFO_OVERRIDE Override the core.userInfo service ENABLE_CORE_URLREADER_OVERRIDE Override the core.urlReader service ENABLE_EVENTS_SERVICE_OVERRIDE Override the events.service service

Commands:
// Create the BackendFeature export const customRootHttpServerFactory: BackendFeature = rootHttpRouterServiceFactory({ configure: ({ app, routes, middleware, logger }) => { logger.info( 'Using custom root HttpRouterServiceFactory configure function', ); app.use(middleware.helmet()); app.use(middleware.cors()); app.use(middleware.compression()); app.use(middleware.logging()); // Add a the custom middleware function before all // of the route handlers app.use(addTestHeaderMiddleware({ logger })); app.use(routes); app.use(middleware.notFound()); app.use(middleware.error()); }, }); // Export the BackendFeature as the default entrypoint export default customRootHttpServerFactory;