Thoughts on Implementing ISR like Next JS

[The-Real-Thisas]

I think for real time news sites and similar that want the performance of SSG without having to rebuild the entire site on every update, this is incredible.

I don't see support in the roadmap but curious if it's on the team's radar by any chance ?

https://nextjs.org/docs/basic-features/data-fetching/incremental-static-regeneration

[fschroiff]

And please make it compatible with all Hosts 🥺

[FredKSchott]

Astro currently has a feature called "hybrid rendering" which lets you mix static, pre-rendered content with dynamic rendered-on-demand content.

You can configure the length of time that a response is cached in your CDN via the Cache-Control header. Astro doesn't currently have a built-in invalidate API for this, but we could add one if there was interest!

[wassfila]

dynamic rerender does not work for e.g. mdx, which still need to be static.

[omerman]

There is interest.

[eric-burel]

For the record, I've explored the SSR (on-demand rendering in Astro wording, dynamic rendering in Next wording, per-request server-side rendering in my own non ambiguous wording :)) + HTTP cache approach a bit: https://blog.vulcanjs.org/treat-your-users-right-with-http-cache-and-segmented-rendering-7a4f4761b549
It's able to mimick static rendering in most useful scenarios, however it should be noted that it falls short in a few specific situations:

• using basic auth (because of the authorization header)
• if you rely on URL rewrites to personalize content (advanced use case but still happens eg for AB tests)

For these a true ISR = caching at the application layer rather than relying on the CDN layer with Cache-control is more suited.

[AkashRajpurohit]

Would recommend this video for anyone who wants to deep dive into understanding the different cache headers and how ISR can be implemented via CDN + cache headers

https://www.youtube.com/watch?v=bfLFHp7Sbkg

[lilnasy]

ISR is going to require different approaches that depend on where you are deploying. I am working on a guide for the docs site that you can track here: withastro/docs#3527 (rendered preview).

Please share how you plan to use ISR and where you deploy so I can better document it.

[lilnasy]

You are right, they are not the same thing.

I think the one difference would be that ISR entails the CDN not evicting the page once built. This is already supported by the netlify adapter and documented in the doc. Cloudflare does not offer a way to make that happen. I haven't looked into what implementing it for Vercel would look like.

[ohrrkan]

Concerning Vercel you can find the diffs in this table https://vercel.com/docs/incremental-static-regeneration#isr-vs-cache-control-comparison-table

[lilnasy]

I should clarify. What I meant was, I could not find their docs for framework developers hoping to implement ISR when deploying to Vercel. I'm pretty sure it can be done with our vercel adapter.

[aretrace]

Your documentation is very helpful, hopefully it can be integrated into the main documentation soon.

[lilnasy]

I'm pretty sure it will be, although it will be framed around "scalability" rather than one specific feature that enables scalability.

[lilnasy]

The vercel adapter now supports Vercel's implementation of ISR. @astrojs/vercel | Astro Docs.

Netlify's equivalent is called On-Demand Builders, and is usable in version 3.1.1 of the official adapter. The current iteration (v4, v5) offers automatic caching that uses standard Cache-Control headers under the hood, instead. The difference from builders is that the cache is per-region, and temporary, instead of global and persistent.

Cloudflare has the infrastructure to offer an equivalent in Cache Reserve, but it is not hooked up to the imperative Cache API available in workers. Your only option is per-region and temporary caching.

For self-hosting, the specifics will depend on the exact set of reverse proxies you are using, but the idea will be to make them save cached responses in object storage.

[bholmesdev]

Looks like this issue has been resolved! We now support adapter-level config for ISR on major platforms that support it, notably Vercel and Netlify. Try it out and feel free to open further discussion for features you'd like to see.

[monaye]

I am curious, if both @astrojs/vercel | Astro Docs and On-Demand Builders will work with the Server Island ?? if so it would nice to documented (I can if someone can confirm).

[heggemsnes]

Awesome that Astro is getting ISR! This seems like the final steps from leaving frustrating Next.js for Astro, but on demand revalidation when? :D Mostly via cache tags would be great.