Be able to extend the request object and middleware / logger instantiation order

[ArtemSkok-Leia]

Problem: I need to include request ID to each of my logs. But in order to implement proper distributed tracing I need to pass it as a http header. However, since the request id header is optional, I would need to generate one, and extend the request object so that this request Id is available in all middlewares and controllers down the pipe.

[RobinTail]

@ArtemSkok-Leia

import { BuiltinLogger, createConfig, createMiddleware } from "express-zod-api";

// Declaring the logger type in use
declare module "express-zod-api" {
  interface LoggerOverrides extends BuiltinLogger {}
}

// Configuring child logger provider
const config = createConfig({
  childLoggerProvider: ({ parent }) =>
    parent.child({ requestId: randomUUID() }),
});

// Accessing child logger context
createMiddleware({
  handler: async ({ logger }) => {
    doSomething(logger.ctx.requestId); // <—
  },
});

I hope it helps to achieve everything.
In case it's not, please clarify with some code samples.

[ArtemSkok-Leia]

Hey, thanks for your response. But in my case I need to do the next:

• request ID should be a property of request
• it should be possible to pass request ID as request header, and if it have not been passed - it should be generated otherwise
• request ID (the same which was passed) should be put in the response headers

[RobinTail]

request ID should be tye property of request

You can do it, @ArtemSkok-Leia
It's the feature of Express types

[ArtemSkok-Leia]

Yeah, but I would not like to modify the request and set the requestId property of it inside of createChildLogger function. Is there a way for me to set the context for all controllers similarly to how we can modify the request object in bare express?

[RobinTail]

I see. So, in your case, the API client defines the request ID and THEN you want to assign it to the logger and use in other places.
Right, @ArtemSkok-Leia ?

[ArtemSkok-Leia]

Yes, you are right. And the request ID is not only a property of a logger insurance, but of the request itself. And this exact request ID is used as a parameter passed with each HTTP request / event sent down the pipe, so that the request trace could be built.

[RobinTail]

@ArtemSkok-Leia ,

what you call "context" is options returned and collected from all the Middleware connected to EndpointsFactory you produce the Endpoint on.

So, if you

would not like to modify the request and set the requestId property of it inside of createChildLogger function

(which is childLoggerProvider config option), then you can do it in a Middleware, like this

export const myFactory = defaultEndpointsFactory.addMiddleware({
  input: z.object({
    requestId: z.string(), // client defines it
  }),
  handler: async ({ input: { requestId }, request, logger }) => {
    (request as any).requestId = requestId;
    const myLogger = logger.child({ requestId });
    return { myLogger, requestId };
  },
});

const myEndpoint = myFactory.build({
  output: z.object({}),
  handler: async ({ options: { myLogger, requestId } }) => ({}),
});