@TCG/Logger

A logging module developed for all js/ts based service of TCG.

Motivation

At present, each microservice operates with its own distinct logging module, leading to noticeable inconsistencies in logging. Improvement in this area has been a collaborative objective for our entire team. The proposed solution we are working towards is the development of a unified logging module. This singular module would be applicable across all microservices, and could also be integrated successfully with a variety of observability tools.

Installation

npm i tcgre-logging

Features

File Transports

There are two file transports, one is combined and another is separated.

Combined

When all the logs are in same file called combined.log

const logProvider = new LoggerBuilder()
  .setCallerPrefix(true)
  .addCombinedFileLogs("<dirName>")
  .build();

Separated

When all the logs are separated by their levels.

const logProvider = new LoggerBuilder()
  .setCallerPrefix(true)
  .addSeparatedFileLogs("<dirName>")
  .build();

Transports

By default it accepts the winstons transports as we are using winston under the hood. So a usecase where we need to add transport for lets say grafana then we will be using winston-loki, by setting it up during application bootstrap and passing to addTransports.

...
 const logProvider = new LoggerBuilder()
    .setCallerPrefix(true)
    .addTransports(
      new winston.transports.Http(),
      new winston.transports.LokiTransport(),
      new winston.transports.DbTransport(),
    )
    .build();
...

Formats

We are using LogForm for formatting our logs. By default, json, errors, timestamp is already setted up, in case, if you want more please refer to the docs for logform.

import {format} from 'logform'
...
const volumeFormat = format((info, opts) => {
  if (opts.yell) {
    info.message = info.message.toUpperCase();
  } else if (opts.whisper) {
    info.message = info.message.toLowerCase();
  }

  return info;
});
...
 const logProvider = new LoggerBuilder()
    .setCallerPrefix(true)
    .addFormats(
      format.cli(),
      volume(),
    )
    .build();
...

LogLevels

So by default the log levels are as such.

const defaultLogLevels = {
  fatal: 0,
  error: 1,
  warn: 2,
  info: 3,
  debug: 4,
};

And default Level is set to debug. Change it using.

...
const loggerProvider = new LoggerBuilder().setLogLevel("info").build();
...

Silencing Console Logs

use the env variable to silence the console logs.

export LOG_SILENT=true;

Attach request ids to request scope

import { NestFactory } from "@nestjs/core";
import { AppModule } from "./app.module";
import { LoggerBuilder } from "tcgre-logging";

async function bootstrap() {
  const logProvider = new LoggerBuilder().setCallerPrefix(true).build();
  const app = await NestFactory.create(AppModule);

  logProvider
    .addRequestScope(app as any) // attaches a request id to all the request.
    .setLogOnUnhandledExceptions() // attaches logger to unhandled rejections
    // and unhandled promised.
    // set application name in case all the logs are collected in the same
    //place.
    .setApplicationName("Pg-Backend apis");

  await app.listen(process.env.PORT || 9000);
}

bootstrap();

Add request context builder

You can add a method that will enable you to select the data related to a request that can be added to the logs.

 logProvider = new LoggerBuilder().setCallerPrefix(true).build();
  const app = await NestFactory.create(AppModule);

  logProvider
    .addRequestScope(app as any, (req, _res) => {
     return {
       path: req.path,
       method: req.method,
       someReallyUsefulHeader: req.headers['x-useful-header'],
     }
   }) // attaches a request id to all the request.
    .setLogOnUnhandledExceptions() // attaches logger to unhandled rejections
    // and unhandled promised.
    // set application name in case all the logs are collected in the same
    //place.
    .setApplicationName("Pg-Backend apis");

  await app.listen(process.env.PORT || 9000);
}

bootstrap();

Add AutoLogs

This will proceed to document all of the methods encapsulated within this class, specifically, it will record the instances of their initiation and termination.

import { EnableClassLogger } from "tcgre-logging";

@EnableClassLogger()
class SomeClassWithMethod {
  method1() {
    return new Date();
  }
}

Add Autologs with all params

This will proceed to document all of the methods encapsulated within this class, specifically, it will record the instances of their initiation and termination but this will also include all the params and return value for those methods

import { EnableClassLogger } from "tcgre-logging";

@EnableClassLogger(true)
class SomeClassWithMethod {
  method1() {
    return new Date();
  }
}

Get logger instance

import { getLogger } from "tcgre-logging";

class SomeClassWithMethod {
  private logger = getLogger(SomeClassWithMethod.name);

  method1() {
    this.logger.debug(
      "Some message",
      new Date(),
      { foo: "bar" },
      "just like console log"
    );

    return;
  }
}

TODO

• [ ] Add better documentation
• [ ] Add jsdocs
• [ ] Add axios interceptors