Using Event Sourced Programming Languages in a Debugger

Video: https://youtu.be/Cxaf8E00GMM
Slides: https://docs.google.com/presentation/d/1sJSqNy-t-kVxzrWlqMTp_03nI7Zo8Znr7k0f0C6L9ig/edit?usp=sharing

Timestamps:

[00:00:00] Intro
[00:02:17] Part 1 - Components: Code Organization for Real Apps
[00:04:26] What we learned from React
[00:07:46] Part 2 - Architecture: Choreography vs Orchestration
[00:13:05] Retries and Timeouts
[00:14:37] Part 3 - Time: React vs Temporal
[00:16:34] Elevator Pitch
[00:17:13] Programming Model
[00:18:44] Comparing React and Temporal Principles
[00:19:11] Live Demo: Amazon One Click Button
[00:23:49] Talk Recap
[00:24:16] React and Temporal Full Comparison
[00:24:42] Conclusion: Enablement

Transcript
 

[00:00:00] Once again, I want to thank you all for tuning in and joining, React New York 2021 without further ado, I'll pass it on to Shawn. 

All right, so hi everyone. 

Hello, React new York. It is my home town in the U S and I miss everyone back in New York. I am currently based in Seattle, but I'm here to talk about React for the Backend. In 2020 I actually thought that I had given my last React talk because I was all tapped out. I had said everything I wanted to say, and then React New York came by and said, do you want to speak? 

And I was like, oh, I really wanted to speak for React New York. So here's my presentation about what I've been working on and what I think the parallels have been for React. And I think there's some generalizable lessons, even if you don't end up using Temporal. So, the inspiration for this talk came from Guillermo Rauch, the creator of Next.js. 

And he was the first person to point out that Temporal.io, does to backend and infra what React did to frontend. Temporal engine is quite complex, much like React, but the surface exposed to developers a beautiful render function and I'm a bit upset because he realized there's before me and I have been working on Temporal for a few months now. 

So important caveats before I start this talk. What I'm presenting to you is alpha for TypeScript. Temporal is typically a goal or Java based application, but we're developing TypeScript and hopefully launching it soon. And then finally "React for the backend" is an analogy, not a design goal. 

 The way I treat this is like, it's a, it's basically like crabs. And one of the most entertaining facts that I've ever found is that nature has apparently tried to evolve crabs five independent times. And in fact, there's a word in evolutionary biology for it called Carcinization. And of course, this is really good for a lot of memes. So tired convergent evolution is not uncommon, especially when species have similar selecting pressures in their environments, wired. 

Everything is Crab. And perhaps everything is React, because we have similar design space problems. So I'll tell a little bit of the story through three parts there's Components, and we'll tell it through the story of Uber, talk about architecture, we'll talk through the story of YouTube, and Time will tell you through the story of Amazon. 

So a lot to cover, I'm going to try to go really fast. Don't worry. I'll share the slides on my Twitter later on. Okay.  

[00:02:17] Part 1 - Components: Code Organization for Real Apps 
 

So part one is about components. You see this a lot on YouTube. Probably you're watching now on YouTube or live streaming. And yeah, you know, like three hour live stream and that's it. 

Very cool. I think we, we know how to break things down and React has really helped us be more productive by being able to break things down into the components and knowing how to compose them together in a predictable way. But there's a lot of things unanswered in things like this in, in full stack, clones of major well-known apps, which is the hard parts. 

What like a typical Uber trip, we'll have all these steps like search pricing match. Pick-up drop-off rating tipping, payment, email, uh, and so on and so forth. And typically the naive way of organizing all this is basically one after the other, right? Like this is search goes to pricing, goes to matching, goes to pick upgoes to dropoff goes to rating goes to tipping goes to payment, goes to email, imagine that these are all managed by separate teams and scaled independently. 

Then you realize, like, this is only the happy path. Then you have to throw in a whole bunch of things that can happen along the way. An Uber trip is basically a long running process with humans in the loop and humans are very, very messy by nature. So how would you write an Uber clone? good luck with a lot of data technologies that you would typically reach for just naively, because you will have to discover all these systems and all these use cases and edge cases along the way. 

So when people say full stack, they often really mean like this half drawn horse meme. I think this is particularly funny so I take every opportunity I can get to show it, but to be honest, a lot of us front end developers are probably the other way the half-drawn Dragon where we're frontend a very good and in the backend, we'll just like, you know, stick some stuff on Firebase and something. 

And in reality, if you look at the backend systems, most companies, especially at scale, go towards some form of very complex micro service, system. I don't have the chart for Uber, but Hail-0 is probably a good comparison. Netflix, Twitter, and It's not really avoidable. If you want to scale a company to any significant size, you probably have to break them up into independent services because you're going to ship your org chart anyway. 

[00:04:26] What we learned from React 
 

The thing I realized as a React developer, as a front end developer, is that actually we had a pretty good run in the past seven, eight years of React in terms of the fact that front end developers know how to organize code at least in terms of the component level. So we moved from the jQuery era where everything was just kind of spaghetti all over the place to at least something more organized where event handlers are strongly tied, locally tied with renders, but essentially managed by React's runtime.  

So a few key lessons from React that I personally draw [00:05:00] is that you want to have a component and a renderer model. Like, so essentially the user or the developer writes components. And then the react core team writes the render and that handles a lot of the boilerplate that you might typically forget. 

And this is everything to do with on mounting or having local states. And it gives you a very nice, non-leaky abstraction that you can write. Second, you can also guarantee work and correctness, which is originally what drew Jordan walk to make something like React because he was working on Facebook messenger and there was a lot of inconsistent state within Facebook manager because of the spaghetti code. 

So correctness, meaning that we embrace functional programming to produce a virtual DOM view is a pure function of state. If you look at the old enough React talks, you will see a lot of v = f(d), so view as a pure function of data. And finally the programming model. We like to say that it's just JavaScript. 

There's no custom syntax ...