The Rocky Journey of Data Fetching Libraries in React’s New Streaming SSR

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If you use the Next.js app directory, you might not even have noticed it, but you are not only using React Server Components, but you are also using the new streaming SSR feature of React.

That means that on first page load, your Client Components will now be server-side rendered, suspense boundary by suspense boundary, and constantly streamed to the client, where they are rehydrated piece-by-piece.


If you combine that with suspense for data fetching in your client components, you will suddenly be facing hydration mismatches - as your client components will start fetching data on the server, but the data will not be transported to the client.


In this talk, I will go over the rocky journey that we had to go through to support suspense for data fetching in Streaming SSR with Apollo Client, looking at all the curious timing problems that come up with these technologies, and how we try to solve them as best as we can - always with the best possible user and developer experience in mind.

Lenz Weber-Tronic
Lenz Weber-Tronic
28 min
20 Oct, 2023

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Video Summary and Transcription

This Talk discusses the journey of data fetching libraries in React's new streaming SSL, focusing on the use of suspense for data fetching. It covers the backstory of suspense and data fetching, the plan and green light for its implementation, challenges with Next.js app router and SSR, data transport and flushing timing, the importance of timing and data transport, delayed rehydration and stream closure, the need for remaining data and required functionalities, challenges faced by vanilla React users, and audience questions about React server components.

Available in Español

1. Introduction

Short description:

Today I'm going to talk about the rocky journey of data fetching libraries in React's new streaming SSL. It's a frustrating topic, but also very interesting. I'm Lancey Bertronick, a senior staff engineer at Apollo GraphQL, working on the TypeScript Apollo client and co-maintaining Redux toolkit. Find me on Twitter as Fry or on GitHub as Frynias.

Today I'm going to talk about—and I have to read this up—the rocky journey of data fetching libraries in React's new streaming SSL, and I'm terribly sorry for the title And I'm terribly sorry for the talk. I wish I wouldn't have to do it, but here we are. And it's a frustrating topic, but it's also very interesting. I was already introduced. I'm Lancey Bertronick. I'm a senior staff engineer at Apollo GraphQL, and I'm working full time on the TypeScript Apollo client. I'm also co-maintainer of Redux toolkit and do a lot of other open source. I have an ADHD. I have more hobbies than you can count. You can find me on Twitter as Fry or on GitHub and the internet generally as Frynias.

2. The Backstory of Suspense and Data Fetching

Short description:

Let's dive into the backstory of how suspense for data fetching in Apollo client started. In October 2018, React Lazy was introduced, allowing lazy importing of files and bundle splitting. A few months later, the hooks APIs were released. In March 2022, React 18 brought concurrent mode and more features, including the renaming of Suspense. However, the use of Suspense for data fetching was still not recommended. In the Apollo client timeline, React Apollo hooks with suspense support was released in October 2018. In September 2019, the hooks were merged into the Apollo client package, marking the first official mention of suspense for data fetching.

So I said, this is a frustrating topic to me. Those always have a backstory. So let's look into a villain backstory here. How did this all start? It started when we wanted to add suspense for data fetching to Apollo client. And coincidentally, in the last talk you already saw that's working. So at this point I could leave a stage and everything's fine. But it didn't always.

So let's go back in history first and talk about suspense first, because this is the thing that actually it wasn't React forever. Why are we talking about this, this year? Shouldn't this have been a thing we stopped thinking or talking about? So let's talk about the history of suspense first. And we go back to October 2018 when the first suspensy thing was introduced in a React and that was React Lazy, which gave you a way of lazily importing files, doing bundle splitting, loading them later and having React kind of fetch the load, like do the loading state for that like behind the scenes without you having to do it. Um, on the same timeline, a few months later, the hooks APIs came out, like in February, 2019. And in March, 2022, this was a big gap. A React 18 came out and essentially the whole thing was like we have concurrent mode now like Suspense was renamed to concurrent mode and got a lot more features at one point and we were really happy and we're like, yeah, we can start doing this now. But then we scrolled down through the release notes and somewhere in that blog article was a footnote. Uh, in React 18, you can start using Suspense for data fetching and opinionated frameworks like Relay, Next.js, Hydrogen and Remix. And that was the depressing part about this ad hoc data fetching with Suspense is technically possible, but still not recommended as a general strategy. And yeah, we, we, we all like every data fetching lever was kind of experimenting with that, but we are a good community and we are listening to our React overlords. So we, we didn't really release anything, uh, uh, especially not on purpose. I think some, some libraries have something for awhile and then saw that sentence afterwards and proofed it out again. Um, so that's like the official react timeline there's of course, there's a second timeline and that's the Apollo client timeline and I want to remember I want you to keep a focus on this October 18 we are in, in the pre hooks times, hooks are not out yet, but there was a conference talk on hooks just. Right now. Um, and we go back to October 18 and someone actually released the library called React Apollo hooks and that library had suspense support using that React lazy workaround. And I, I, honestly, I was flabbergasted when I looked that up because I wasn't aware of that preparing this. And I just want to say, like, I don't know who did that, but kudos to that person. You are amazing. Um, that was a really, really cute, cool experiment. Um, and in September, 2019, so like half a year after the react hooks came out, and a little while after the Apollo hooks had been in beta for a while, uh, there was an issue where we merged the, uh, the hooks into the real Apollo client package. And that was the first official mention of suspense that I could find in our issues. That was issue 5,357. And it says when react suspense and data fetching approach finalizes.

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