Cache Assets #

Fetch network resources and cache them so you don’t bombard your API (or other resources). Do this at configurable intervals—not with every build! Once per minute, or once per hour, once per day, or however often you like!

With the added benefit that if one successful request completes, you can now work offline!

This plugin can save any kind of asset—JSON, HTML, images, videos, etc.

• Fetch a remote URL and saves it to a local cache.
• If the remote server goes down or linkrots away—we keep and continue to use the local asset (save remote images!)
• If cache expires and the network connection fails, will continue to use the cached request and make a new request when the network connectivity is restored.
• Control concurrency so we don’t make too many network requests at the same time.
• Requires Node 10+
• eleventy-cache-assets on GitHub

Installation #

• eleventy-cache-assets on npm

npm install @11ty/eleventy-cache-assets

Usage #

Cache a JSON file from an API #

Consider the following example, perhaps in an Eleventy Global Data File.

const Cache = require("@11ty/eleventy-cache-assets");

module.exports = async function() {
  let url = "https://api.github.com/repos/11ty/eleventy";

  /* This returns a promise */
  return Cache(url, {
    duration: "1d", // save for 1 day
    type: "json"    // we’ll parse JSON for you
  });
};

Options #

Change the Cache Duration #

After this amount of time has passed, we’ll make a new network request to the URL to fetch fresh data. The duration option currently supports the following shorthand values:

• s is seconds (e.g. duration: "43s")
• m is minutes (e.g. duration: "2m")
• h is hours (e.g. duration: "99h")
• d is days
• w is weeks, or shorthand for 7 days (e.g. duration: 2w is 14 days)
• y is years, or shorthand for 365 days (not exactly one year) (e.g. duration: 2y is 730 days)

Type #

• type: "json"
• type: "text"
• type: "buffer" (default: use this for non-text things)

Cache Directory #

The directory option let’s you change where the cache is stored. It is strongly recommended that you add this folder to your .gitignore file.

const Cache = require("@11ty/eleventy-cache-assets");

Cache("https://…", {
	directory: ".cache"
});

Remove URL query params from Cache Identifier #

(Version 2.0.3 and newer) If your fetched URL contains some query parameters that aren’t relevant to the identifier used in the cache, remove them using the removeUrlQueryParams option. This is useful if an API adds extra junk to your request URLs.

• removeUrlQueryParams: true (false is default)

const Cache = require("@11ty/eleventy-cache-assets");

Cache("https://www.zachleat.com/img/avatar-2017-big.png?Get=rid&of=these", {
	removeUrlQueryParams: true
});

What happens with a request fails? #

1. If this is the first ever request to this URL (no entry exists in your cache folder), it will fail. Use a try/catch if you’d like to handle this gracefully.
2. If a failure happens and a cache entry already exists (even if it’s expired), it will use the cached entry.

const Cache = require("@11ty/eleventy-cache-assets");

module.exports = async function() {
	try {
    let url = "https://api.github.com/repos/11ty/eleventy";

		/* This returns a promise */
		return Cache(url, {
			duration: "1d",
			type: "json"
		});
	} catch(e) {
		return {
			// my failure fallback data
		}
	}
};

Running this on your Build Server #

If you’re attempting to use this plugin on a service like Netlify and you are definitely not checking in your .cache folder to git, note that the cache will be empty with every build and new requests will go out. It’s important to be aware of this, even if it’s what you want for your production build!

More Examples #

Cache a Remote Image #

This is what eleventy-img uses internally.

const Cache = require("@11ty/eleventy-cache-assets");

module.exports = async function() {
  let url = "https://www.zachleat.com/img/avatar-2017-big.png";
  let imageBuffer = await Cache(url, {
    duration: "1d",
    type: "buffer"
  });
  // Use imageBuffer as an input to the `sharp` plugin, for example

  // (Example truncated)
}

Fetch Google Fonts CSS #

Also a good example of using fetchOptions to pass in a custom user agent. Full option list is available on the node-fetch documentation.

const Cache = require("@11ty/eleventy-cache-assets");

let url = "https://fonts.googleapis.com/css?family=Roboto+Mono:400&display=swap";
let fontCss = await Cache(url, {
	duration: "1d",
	type: "text",
	fetchOptions: {
		headers: {
			// lol
			"user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
		}
	}
});

Fetching GitHub Stars for a repo #

• This specific example has been previously described in our quick tips section: head over to read Quick Tip #009—Cache Data Requests.

Manually store your own data in the cache #

You probably won’t need to do this. If you’d like to store data of your own choosing in the cache (some expensive thing, but perhaps not related to a network request), you may do so! Consider the following Global Data File:

const {AssetCache} = require("@11ty/eleventy-cache-assets");

module.exports = async function() {
  // Pass in your unique custom cache key
  // (normally this would be tied to your API URL)
  let asset = new AssetCache("zachleat_twitter_followers");

  // check if the cache is fresh within the last day
  if(asset.isCacheValid("1d")) {
    // return cached data.
    return asset.getCachedValue(); // a promise
  }

  // do some expensive operation here, this is simplified for brevity
  let fakeTwitterApiContents = { followerCount: 1000 };

  await asset.save(fakeTwitterApiContents, "json");

  return fakeTwitterApiContents;
};

Change Global Plugin Concurrency #

const Cache = require("@11ty/eleventy-cache-assets");
Cache.concurrency = 4; // default is 10

Command line debug output #

DEBUG=EleventyCacheAssets* node your-node-script.js
DEBUG=EleventyCacheAssets* npx @11ty/eleventy

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