[Chore] Enable caching

[samkahchiin]

Summary

Customise caching in the cloudflare worker script.
This PR sets two Page Rules: Edge Cache TTL and Cache Level (to Cache Everything) using the request url as the cacheKey on the processed request

Edge Cache TTL VS Browser cache Expire TTL here
=> Browser cache TTL

Browser cache expire TTL is the time that CloudFlare instructs a visitor's browser to cache a resource. Until this time expires, the browser will load the resource from its local cache thus speeding up the request significantly. CloudFlare will respect the headers that you give us from your web server, and then we will communicate with the browser based on the time selected in this drop down menu.

=> Edge Cache TTL

how long CloudFlare's edge servers will cache a resource before requesting a fresh copy from your server. When you create a Cache Everything Page Rule, you now may choose whether to respect all existing headers or to override any headers that are in place from your server. By overwriting the headers, CloudFlare will cache more content at the CloudFlare edge network, decreasing load to your server.

Unfortunately, edge cache TTL would not be reflected in the response header. See here

Edge Cache TTL isn't visible in response headers.

Regarding html caching
The Cloudflare router by default does not cache html file by default

Cloudflare only caches based on file extension and not by MIME type. The Cloudflare CDN does not cache HTML by default

See here

Setting cacheEverything to true to allow html file to be cached by Cloudflare as well.
https://developers.cloudflare.com/workers/runtime-apis/request#requestinitcfproperties

This option forces Cloudflare to cache the response for this request, regardless of what headers are seen on the response. This is equivalent to setting the Page Rule Cache Level (to Cache Everything). Defaults to false. This option applies to GET and HEAD request methods only.

TODO

• Should make this as optional choices as it might not work well in some cases
• Setting cacheEverything to true can be dangerous for dynamic pages. Investigate how it affect the current setup
  • Solution: Limit cloudflare worker to only cache request which match the specified routes

References

• https://blog.cloudflare.com/edge-cache-expire-ttl-easiest-way-to-override/
• How to configure CDN using workers script
• https://developers.cloudflare.com/workers/learning/how-the-cache-works/

[swiknaba]

Generally LGTM, thanks! Tested on our test application, loading some resources is broken now. See the comment from @puckzxz , that should fix it 🙂

[swiknaba]

Solution: Limit cloudflare worker to only cache request which match the specified routes

Makes sense!

Thanks!

Left a few minor clean up suggestions

[swiknaba]

LGTM