Remote Rendering with Web Workers

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Learn how we built Argo, a powerful extensibility framework that allows developers to seamlessly extend Shopify's apps on every platform. Argo provides developers with APIs to execute behaviour on the main app and a component library that renders native UI identical to Shopify's own component whether it's on iOS, Android or Web. Behind the scenes, Argo uses web workers and an open sourced library called remote-ui to create a sandboxed execution environment for external scripts.

Trish Ta
Trish Ta
32 min
14 May, 2021

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Video Summary and Transcription

Today's Talk discussed the development of Argo, a framework for remote rendering of content within Shopify's apps. The core concepts include creating a JavaScript sandbox, implementing a remote procedure call layer, and using proxies. The Talk explored the end-to-end flow of rendering content, the construction of the worker script, the rendering of UI components, and the advantages of remote rendering for security and flexibility. The Talk also touched on the challenges faced and the open-source nature of the project.

Available in Español: Renderizado remoto con Web Workers

1. Introduction to Remote Rendering with Web Workers

Short description:

Today, I will walk you through how we built Argo, an extensible framework that allows rendering of remote content inside of Shopify's apps. The core concepts behind remote rendering include creating a JavaScript sandbox, implementing a remote procedure call layer, and using proxies. We aimed to enable remote rendering, provide a good user experience, a good developer experience, and a security layer.

Hi, everyone. My name is Trish Thao. Thanks for joining me for this talk about remote rendering with web workers. Today, I will walk you through how we built Argo, an extensible framework that allows rendering of remote content inside of Shopify's apps.

Here's what we'll be covering today. I'll talk about the core concepts. How we built Argo, the end-to-end flow, how we can swap out React. And I'll follow up by having a quick demo of all the pieces working together.

Here are the core concepts behind remote rendering. First, we need to create a JavaScript sandbox. This sandbox allows us to securely execute code in a background thread. The communication to the main thread can be achieved by sending messages. This is implemented as a web worker on web. On iOS and Android, this is implemented as a headless JavaScript engine. Next, we need to implement a remote procedure call layer, RPC for short. This is a protocol that enables one program to call the service in another program. Finally, we make use of proxies. A proxy is a wrapper that intercept and redefines the target's core operations, such as invoking functions or accessing properties.

I'll talk about how we built Argo. First of all, what we were trying to achieve is to enable remote rendering. What this means is allowing an external script to define the UI, and then let the main application render it natively. The framework allows the external script to exchange data with the main application. That results in UI being rendered and custom behavior to be executed. So the objectives we were trying to achieve are to provide a good user experience. Injected UI content is indistinguishable from Shopify's own native content on all platforms. We wanted to provide a good developer experience. External scripts can be built using familiar languages like JavaScript and TypeScript, and frameworks like React or Vue, and we also wanted to provide a security layer. The external script can only access and execute APIs provided by Shopify. At a high level, this isn't what we were trying to do. We have a JavaScript sandbox that loads an external script inside of it.

2. End-to-End Flow of Rendering Content

Short description:

Through an RPC proxy, the script can call the RenderUI inside the main application. Argo was built on top of a library called RemoteUI, which provides a communication layer, a remote component tree, and a proxy layer. The end-to-end flow involves setting up the worker, loading the external script, constructing the UI, and rendering it. The setup includes creating a worker, setting up the RPC layer, and establishing a communication channel. The receiver manages the component tree, and the controller specifies the UI implementation. Finally, the remote renderer converts the component tree into UI.

Through an RPC proxy, the script can call the RenderUI inside the main application. When a user interacts with the UI, for example, clicking on a button, if the handler is defined inside the external script, the main application can call the handler through the RPC layer.

Argo was built on top of a library called RemoteUI. This library provides the following. A communication layer between the JavaScript sandbox and the main application. A remote component tree that the external script can operate on and the host can render. A proxy layer to allow the host to call functions defined in the JavaScript sandbox and vice versa.

Now I'll talk to you about the end to end flow of how rendered, how rendered, how the content is rendered. On web, first the host does some set up steps to set up the worker. Then we load the external script. And then the external script constructs UI using our libraries. Then it calls the render. This results in the host receiving a message with the serialized component tree, which is finally rendered as UI.

Digging into the whole setup, we are building an extension component that can communicate with a web worker. We start by setting up the worker and the RPC layer. We create a worker with a worker.js file. I'll dive deeper into what this is later. And then we call create endpoint to create a communication channel between the host and a worker. This create endpoint function is provided by Remote UI. And then we return the extension. The endpoint call method. This is a proxy that allows functions from inside the worker to be executed by the host asynchronously via message passing.

Next we set up an instance of the remote receiver. This receiver manages an internal component tree that can be operated on in response to messages. We also set up a controller which specifies the implementation to use when rendering UI. In this example, we are allowing buttons to be rendered using the button component from the Polaris UI library. The host gets to decide which components will be used. This makes it possible to swap out components depending on what's needed.

The last step is to render the remote renderer component from the remote UI library and pass it the receiver and controller. The remote render is responsible for converting the component tree it receives into UI using the implementation specified by our controller.

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