Implement HTTP caching to the webserver

[AuroraLS3]

I would like to be able to..

Speed up page loading times on subsequent visits.

Is your feature request related to a problem? Please describe.

Opening the Plan website from a far away (latency) webserver takes longer to get the required javascript and json files. Some of these could already be cached by the browser.

https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching

This can take seconds off the loading time when webserver is on another continent to the user.

Following can be considered cacheable:

• React bundle files (The resource files do have a last modified date attached to them, either via assetVersions.yml or from files on disk)
• json_cache contents (They have timestamps tied to them)

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Notes from the linked article

• Use Cache-Control: private header when content is based on cookies
• Cache-Control: max-age=seconds can be used to define how long response is valid - longer values could be used for bundles
• ETag: <tag> and If-None-Match: <tag> can be used with 304 Not Modified to use the cached version of files. "servers are free to set the value based on whatever means they choose."
  • Cases where request has no cache stuff in it should also be dealt with (Fresh loads, reloads etc)
• "considering the overall HTTP ecosystem, it is preferable to provide both ETag and Last-Modified."
• If something is not to be cached use Cache-Control: no-cache, private

Based on this following could be implemented:

• For index.html, Cache-Control: no-cache; Last-Modified: ...; Etag: ... https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching#main_resources
• For react bundle files, Cache-Control: max-age: 2592000; Last-Modified: ...; Etag: <timestamp> - Caching for a month, causes no issues since bundle files have hash in filenames
• For json, Cache-Control: no-cache, private; Last-Modified: ...; Etag: <timestamp> - This should allow returning a 304 until queries finish. Needs to be checked.

[AuroraLS3]

The json request caching requires moving the request time timestamp out of the URL since URL is used as the cache key on the browser