Cloudflare Workers environment variables and context

Cloudflare Workers does not set environment variables a global object like Node.js does with process.env. Workers binds environment variables to the worker's special fetch event handler thought a specific env argument.

This means accessing environment variables within Inngest function handlers isn't possible without explicitly passing them through from the worker event handler to the Inngest function handler.

We can accomplish this by use the middleware feature for Workers or when using Hono.

Creating middleware

You can create middleware which extracts the env argument from the Workers fetch event handler arguments for either Workers or Hono:

1. Use onFunctionRun's reqArgs array to get the env object and, optionally, cast a type.
2. Return the env object within the special ctx object of transformInput lifecycle method.

import { Inngest, InngestMiddleware } from 'inngest';

const bindings = new InngestMiddleware({
  name: 'Cloudflare Workers bindings',
  init({ client, fn }) {
    return {
      onFunctionRun({ ctx, fn, steps, reqArgs }) {
        return {
          transformInput({ ctx, fn, steps }) {
            // reqArgs is the array of arguments passed to the Worker's fetch event handler
            // ex. fetch(request, env, ctx)
            // We cast the argument to the global Env var that Wrangler generates:
            const env = reqArgs[1] as Env;
            return {
              ctx: {
                // Return the env object to the function handler's input args
                env,
              },
            };
          },
        };
      },
    };
  },
});

// Include the middleware when creating the Inngest client
export const inngest = new Inngest({
  id: 'my-workers-app',
  middleware: [bindings],
});

Within your functions, you can now access the environment variables via the env object argument that you returned in transformInput above. Here's an example function:

const myFn = inngest.createFunction(
  { id: 'my-fn' },
  { event: 'demo/event.sent' },
  // The "env" argument returned in transformInput is passed through:
  async ({ event, step, env }) => {

    // The env object will be typed as well:
    console.log(env.MY_VAR);
  }
);