Gatsby: Speed up Netlify builds with caching

[jlengstorf]

Summary

Netlify has an undocumented feature that allows a persistent cache between builds. For sites that are generating a lot of image thumbnails and other time-intensive tasks, being able to cache that work between builds could be a huge time saver.

The feature isn't documented, but two examples exist that we can pull from:

• This article from Contentful includes caching example code
• @philhawksworth shared a demo project that leverages Netlify's cache for faster builds

From a conversation with @KyleAMathews, it sounds like gatsby-plugin-netlify could potentially leverage this cache (either by copying the caches or symlinking) to make subsequent Gatsby builds on Netlify _significantly_ faster.

Motivation

Generating images takes a lot of time and doesn't require duplicate work between builds. Gatsby already has a great cache, so if we can get Netlify to persist that cache between builds, we're able to get a big speed boost for Gatsby developers using Netlify with a relatively low effort.

[axe312ger]

hmm... "done" 😅

see #5662

[axe312ger]

As discussed on Discord, this won't be merged into the Gatsby core repository.

I published it to npm and created a separate repo. Lets continue over there:

• https://www.npmjs.com/package/gatsby-plugin-netlify-cache
• https://github.com/axe312ger/gatsby-plugin-netlify-cache

I guess we can close this issue and do further discussions within the other repo @jlengstorf

[jlengstorf]

Sounds good. Thanks again for taking the lead on this, @axe312ger!