如何在其他类中使用 fastify 请求记录器而无需将其作为参数传递？

Question

I'm new in nodejs, I'm using fastify and I want to be able to use the req.logger in all the classes functions of the flow, this because I have a the request-id on req.logger, the first solution that came to my mind is to pass as a parameter the logger through all the function/classes but I think that would make the code kind of dirty, here is an example of my code:

app.ts

import pino from 'pino';
import fastify from 'fastify';

declare module 'fastify' {
  interface FastifyInstance {
    // augment fastify instance with the config object types
    config: Config;
  }
}

function build() {

  const app = fastify({
    logger: pino({
      name: process.env.NAME,
      level: process.env.LOG_LEVEL,
    }),
    disableRequestLogging: true,
    requestIdHeader: 'correlation-id',
    requestIdLogLabel: 'correlationId',
  });
  // register plugins 
  
  app.register(apiRoutes, fastify => ({
    getObjectUseCase: new GetObjectUseCase(
      new TestClass()),
  }));

  return app;
}
export { build };

routes.ts

import { FastifyPluginCallback } from 'fastify';
import { StatusCodes } from 'http-status-codes';

export const apiRoutes: FastifyPluginCallback<RoutesOpts> = async (fastify, options, done) => {
  const getObjectUseCase = options.getObjectUseCase; 

  fastify.get<object>('/v1/api/:id', async (req, reply) => {
    const id = req.params.payoutId;
    req.logger.info('This is a logger print'); // has the correlation id inside it while printing
    const storedObject = await getObjectCase.execute(id);
    reply.code(StatusCodes.OK).send(storedObject);
  });
}

GetObjectUseCase.ts

export class GetObjectUseCase {
  private anotherClass: TestClass;

  constructor(anotherClass: TestClass) {
    this. anotherClass = anotherClass;
  }

  async execute(id: string): Promise<StoredObject> {
    // I want to use the logger here with have the correlation id on it without having to pass it as an argument on the method, how is it posible?
    return this.anotherClass.getById(id);
    // also needed to use it inside anotherClass.getById so I will need to pass the logger also in the method

  }
}

Hope I have been clear. Thanks!

Answer 1

This may not be the best or only way to do it, but this has worked for me in the past.

Typically I structure my projects with an app.ts that just instantiates my FastifyInstance and then exports the log from that created instance. This allows me to use the log where ever I want to.

It looks something like this.

app.ts

import fastify from 'fastify';

const app = fastify({ logger: true /* Your logging configuration */});

export default app;
export const logger = app.log; // Allows me to log where ever I want.

server.ts

import app from './app';

... // All your fastify configuration and other stuff.

app.listen({ ... });

Now I can use the logger outside of fastify stuff.

get-object-use-case.ts

import { logger } from './app'; // Import your fastify logger to use in this class.

export class GetObjectUseCase {
  private anotherClass: TestClass;

  constructor(anotherClass: TestClass) {
    this. anotherClass = anotherClass;
  }

  async execute(id: string): Promise<StoredObject> {
    logger.info({/* Whatever you want to log here. */}); // Now you can use the logger here.
    return this.anotherClass.getById(id); // You can just import the logger into the TestClass file to get logging enabled there.
  }
}

This even allows you to log before your FastifyInstance is started. Check out this codesandbox for a running example.