Implementing distributed logging

Once we have created a distributed system, everything gets more complicated. One of the things that becomes more complicated is logging and tracing a request across multiple microservices. In Chapter 11, we covered distributed logging – this is a technique that allows us to trace all the log lines that are relevant to a specific request flow via the use of correlation IDs (reqId). In this section, we will put that into practice.

First, we modify our gateway’s server.js file to generate a new UUID for the request chain, like so:

const crypto = require('crypto')
const fastify = require('fastify')({
  logger: true,
  genReqId (req) {
    const uuid = crypto.randomUUID()
    req.headers['x-request-id'] = uuid
    return uuid
  }
})

Note that we generate a new UUID at every request and assign it back to the headers...