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d2l-fetch-simple-cache

Provides a middleware function for caching fetch responses for the same url+auth combination.

WARNING: This middleware ignores server Response cache-control directives and should be used with caution.

Setup

npm install

Usage

Reference the script in your html after your reference to d2l-fetch (see here for details on d2l-fetch):

Install d2l-fetch-simple-cache via npm:

npm install d2l-fetch-simple-cache
import { fetchSimpleCache } from 'd2l-fetch-simple-cache';

Simple-cache

Install the simple-cache middleware to d2lfetch via the use function and then start making your requests.

d2lfetch.use({name: 'simple-cache' fn: fetchSimpleCache});

const response = await d2lfetch.fetch(
  new Request('http://example.com/api/someentity/')
);

Responses are cached based on the combination of method, url and Authorization request header value. Any request that matches an existing cached item based on this combination will not result in a subsequent network request but will rather be given a promise that resolves to a clone of the original cached request's Response.

Options

As of d2l-fetch v1.2.0 it is possible to provide configuration options during middleware setup. d2l-fetch-simple-cache accepts the following options arguments:

  • cacheLengthInSeconds: This can be used to override the default cache length. (Default is 120 seconds)
//cache responses for 5 minutes
d2lfetch.use({
	name: 'simple-cache',
	fn: simpleCache,
	options: { cacheLengthInSeconds: 600 }
});
  • methods: This can be used to override the default http methods that are allowed to be cached. (Default is ['GET', 'HEAD', 'OPTIONS'])
//only cache responses from GET requests
d2lfetch.use({
	name: 'simple-cache',
	fn: simpleCache,
	options: { methods: ['GET'] }
});

Cache-Control

By default d2l-fetch-simple-cache will cache responses for 2 minutes, or the time provided at setup in the cacheLengthInSeconds option parameter (see Options above). This can be modified on a Request-level basis by supplying arguments in the cache-control header of the Request. The following values are accepted:

  • cache-control: no-cache will effectively 'bust' the cache. Any matching cached Response will be removed from the cache and the Request will continue through the middleware chain. Note that the Response will still be cached for future requests (assuming they don't also contain a no-cache directive).
  • cache-control: no-store will indicate that the Response returned from the server should not be cached. Note that this does not prevent the Request from being served from an existing valid cached Response.
  • cache-control: max-age=<seconds> can be used to override the configured middleware time-to-live. For example if the middleware is configured with the default 2 minute TTL a Request sent with a header of cache-control: max-age=60 will only be cached for 60 seconds. Note that if a previous matching Request had already been cached the shorter of the two values (middleware configuration and max-age header value) will be used for determining cache expiry.

Versioning and Releasing

This repo is configured to use semantic-release. Commits prefixed with fix: and feat: will trigger patch and minor releases when merged to main.

To learn how to create major releases and release from maintenance branches, refer to the semantic-release GitHub Action documentation.