This task is about implementing a minimal service that essentially composes an HTTP response based on multiple other resources that are themselves more cacheable and less variable. Initial version requirements:
- High-throughput. Suitable for handling traffic at the edge, essentially doing only HTTP and string manipulation.
- Request routing.
- HTML Templating. Fetch, precompile and cache templates - presumably Mustache.
- Streamable. Must implement template handling so flushing starts early and continues progressively.
- Export as ServiceWorker. Add an endpoint that exports a JavaScript program compatible with a ServiceWorker that contains all the utilities (elematch, mustache etc.), Router, RequestHandler, and the current install's router configuration and custom RequestHandlers.
Related:
- https://jakearchibald.com/2016/streaming-template-literals/
- https://github.com/digitaldesignlabs/talisman
- https://github.com/wikimedia/elematch
It should probably use service-runner and not be specific to MediaWiki in anyway. We can later use this library in a MediaWiki-specific installation that extends certain base classes and provides relevant configuration.
Due to unsolved technical debt (see T111588#2416137), I suggest the initial implementation is used for a less complicated use case. The Wikipedia.org portal, for example, which needs localisation in a performant way. Currently done client-side with XHR and causes a FOUC.
Draft spec by @GWicke and @Krinkle:
- node-serviceworker-server: Node library that runs an HTTP service. It can be configured to map a domain and request scope to a service worker url. The service will use the node-serviceworker library to turn the service worker script into something that we can instantiate and make a request to on the server-side.
- Status: Concept
- node-serviceworker: Node library that provides a Node sandbox with several browser APIs available in its scope (such as Fetch, ServiceWorker Cache, and more).
- Status: Work in progress (https://github.com/gwicke/node-serviceworker)
- sw-wikimedia-helpers: Collection of utilities we expect most of our ServiceWorker clients to need. Such as request routing, view abstraction, and a command-line script to generate a compact sw.js file. This utility library will likely make use of:
- browserify
- mixmaster: Produce a readable stream from an array of string literals, functions, promises, and other streams. With the option to pass through one or more transforms. This allows progressively streaming to the client with the ability to dynamically substitute portions, and to precompile any templates.
- elematch: Efficient matching of elements in a stream of HTML. To be used with Mixmaster. This would allow to progressively stream to the client with the ability to dynamically substitute portions.
- musti: Streamable Mustache renderer. Uses Mixmaster.