Mashroom Virtual Host Path Mapper

Plugin for Mashroom Server, a Microfrontend Integration Platform.

This plugin adds the possibility to map external paths to internal ones based on virtual host. This is required for web-apps that need to know the actual "base path" to generate URLs (in that case rewriting via reverse proxy won't work).

For example Mashroom Portal can use this to move Sites to different paths but keep the ability to generate absolute paths for resources and API calls. Which is useful if you want to expose specific Sites via a virtual host.

Usage

If node_modules/@mashroom is configured as plugin path just add @mashroom/mashroom-vhost-path-mapper as dependency.

To map for example a portal site to www.my-company.com/web configure the reverse proxy like this:

www.my-company.com/web -> <portal-host>:<portal-port>/

and the plugin like this:

{
  "plugins": {
       "Mashroom VHost Path Mapper Middleware": {
           "considerHttpHeaders": ["x-my-custom-host-header", "x-forwarded-host"],
           "hosts": {
              "www.my-company.com": {
                 "frontendBasePath": "/web",
                 "mapping": {
                    "/login": "/login",
                    "/": "/portal/public-site"
                 }
              },
              "localhost:8080": {
                 "mapping": {
                     "/": "/local-test"
                 }
              }
          }
       }
    }
}

That means if someone accesses Mashroom Server via https://www.my-company.com/web/test the request will hit the path /portal/public-site/test.

It also works the other way round. If the server redirects to /login it would be changed to /web/login (in this example).

Port based virtual hosts (like localhost:8080) are also possible but only if the request still contains the original host header (and no X-Forwarded-Host different from the host header).

The mapping rules do not support regular expressions.

The frontendBasePath is optional and / by default.

The considerHttpHeaders property is also optional and can be used to detect the host based on some custom header. The first header that is present will be used (so the order in the list specifies the priority).

Services

MashroomVHostPathMapperService

The exposed service is accessible through pluginContext.services.vhostPathMapper.service

Interface:

export interface MashroomVHostPathMapperService {
    /**
     * Reverse map the given server url to the url as seen by the user (browser).
     * The given URL must not contain host, only path with query params and so on.
     */
    getFrontendUrl(req: Request, url: string): string;

    /**
     * Get the details if the url of the current path has been rewritten
     */
    getMappingInfo(req: Request): RequestVHostMappingInfo | undefined;
}