Enhancing Inngest: AsyncLocalStorage & Middleware Compatibility

Hey folks! Let's dive into a common challenge when working with Inngest, especially when you're dealing with asynchronous operations and need to keep track of context. We're talking about AsyncLocalStorage and how to make it play nicely within your Inngest functions and steps. If you're scratching your head, wondering how to make things work smoothly, you're in the right place. This article will explore the problem, the proposed solution, and some alternative approaches to get you up and running without a hitch.

The Problem: Async Nature and Middleware Limitations

So, what's the deal? Well, the core issue stems from the asynchronous nature of how Inngest handles function invocations and steps. When you're dealing with asynchronous code, maintaining context across different parts of your application can be tricky. This is where AsyncLocalStorage comes to the rescue. It's a Node.js module that allows you to store contextual information, like user IDs, request details, or other important data, and access it anywhere within your asynchronous code. The problem arises because Inngest's current middleware implementation doesn't provide a straightforward way to wrap your functions with AsyncLocalStorage.run(). This function is essential for creating a new context and ensuring that the data stored in AsyncLocalStorage is correctly propagated through your asynchronous calls. As a result, you might find yourself manually wrapping every relevant function call, which can be cumbersome and error-prone. This manual wrapping is not only tedious but also increases the risk of mistakes, especially in complex applications with many asynchronous operations. The lack of direct support for AsyncLocalStorage in the middleware lifecycle also complicates the process of integrating context-aware logging, tracing, and other functionalities that rely on the correct propagation of contextual data. It can also lead to issues with concurrency, as the context can get overwritten if not managed properly.

Why is this important?

Because maintaining context is crucial. Imagine you're building a system that processes user orders. You need to know which user initiated the order at every step of the process – from initial request to database updates and sending confirmations. Without a reliable way to maintain context, you could end up with incorrect data, security vulnerabilities, and a frustrating user experience. AsyncLocalStorage provides a clean and efficient way to achieve this, but it requires proper integration with your application's architecture.

The Proposed Solution: Empowering Middleware

The most elegant solution, as suggested, involves enhancing the middleware capabilities within Inngest. The idea is to allow middleware to wrap the main function, failure function, or steps function with AsyncLocalStorage.run(). This would enable you to easily create and manage the context needed for your asynchronous operations. The proposed change to the middleware implementation would provide a transformInput hook within the onFunctionRun lifecycle stage. This hook would allow you to modify the function itself before it's executed, injecting the AsyncLocalStorage.run() wrapper.

Code Example Breakdown

Let's break down the code example to see how this works in practice:

const myImportantContext = new AsyncLocalStorage<string>();
const addContextMiddleware = new InngestMiddleware({
 name: "Add Context",
 init({ client, fn }) {
 return {
 onFunctionRun({ ctx, fn, steps }) {
 const context = "We're running in context now!";

 return {
 transformInput({ ctx, fn, steps }) {
 return {
 fn: myImportantContext.run(context, fn)
 }
 },
 };
 },
 };
 },
});

• myImportantContext: This is an instance of AsyncLocalStorage that stores a string value representing our context. You can adapt this to store whatever contextual data you need.
• addContextMiddleware: This creates a new middleware that adds the context. The init function is called when the middleware is initialized.
• onFunctionRun: Within onFunctionRun, we define the context that we want to run.
• transformInput: This is where the magic happens. The transformInput hook allows us to wrap the original function (fn) with myImportantContext.run(context, fn). This ensures that the function is executed within the context of AsyncLocalStorage. The context string is passed as the first argument to run(), and the original function (fn) is passed as the second argument. This ensures that the original function is executed within the context created by AsyncLocalStorage. This approach is clean and ensures that the context is correctly propagated through all asynchronous calls made by the function. It is important to remember that using transformInput allows for a non-intrusive way of injecting the context into the execution flow, without modifying the function code itself.

Benefits of this approach:

• Cleaner Code: No need to manually wrap every function call.
• Reduced Errors: Reduces the risk of context-related bugs.
• Improved Maintainability: Makes your code easier to read and maintain.

Exploring Alternative Approaches

Of course, there are alternative ways to tackle this problem, but they come with their own set of challenges.

1. The AsyncLocalStorage.enterWithStore Method

One approach is using AsyncLocalStorage.enterWithStore. The issue with it is that it's prone to issues with concurrency. It can lead to overwriting the context, which defeats the purpose of managing context. This can lead to subtle bugs that are hard to track down.

2. Manual Wrapping

The other alternative is manually wrapping all relevant calls with .run(). This involves explicitly wrapping each function call with AsyncLocalStorage.run(), passing in the context and the function itself. While this approach works, it's cumbersome, requires careful implementation, and increases the likelihood of errors.

The Drawbacks of the Alternatives

• Complexity: Manual wrapping can make your code more complex and harder to read.
• Risk of Errors: It's easy to miss a call or make a mistake, leading to context-related bugs.
• Maintainability: Manual wrapping can make it harder to maintain your codebase.

Conclusion: Streamlining Asynchronous Context

In a nutshell, enhancing Inngest's middleware capabilities to support AsyncLocalStorage would be a massive win for anyone working with asynchronous operations. The proposed solution provides a clean, efficient, and less error-prone way to manage context within your Inngest functions and steps. While there are alternative approaches, they often come with increased complexity and potential for errors. By embracing middleware-based context management, Inngest can provide a more robust and user-friendly experience for developers, especially those dealing with complex asynchronous workflows. The goal is to make it easier to maintain context across all parts of your application, ensuring that your code behaves as expected and that you can debug any issues more efficiently.