json-logger-service

Provides a Json Nest LoggerService.

Installation

$ npm i json-logger-service --save

Usage

Nest.js compatibility matrix

Nest.js version	json-logger-service compatible version
9.x.x	9.x.x
8.x.x	8.x.x
7.x.x	7.x.x

Nest Json LoggerService implementation use

Configuring Nest to use a custom Json LoggerService.

import {NestFactory} from '@nestjs/core';
import {AppModule} from './app.module';
import {JsonLoggerService} from 'json-logger-service';

const bootstrap = async () => {
    const app = await NestFactory.create(AppModule);
    app.useLogger(new JsonLoggerService('NestServer'));
    await app.listen(3000);
};
bootstrap();

Using a new Json logger in your classes

import {JsonLogger, LoggerFactory} from 'json-logger-service';

export class HelloWorldService {
    private readonly logger: JsonLogger = LoggerFactory.createLogger(HelloWorldService.name);

    public getHello(): string {
        this.logger.info('Hello World!');
        this.logger.info({myContextProperty: 'My property\'s value', anotherProperty: 'Another value'}, 'Hello World with some context!');
        return 'Hello World!';
    }
}

Use Express request logger

Configuring Nest to use a simple Express request logger.

import {NestFactory} from '@nestjs/core';
import {AppModule} from './app.module';
import {RequestLogger} from 'json-logger-service';

const bootstrap = async () => {
    const app = await NestFactory.create(AppModule);
    ...
    app.use(RequestLogger.buildExpressRequestLogger());
    ...
    await app.listen(3000);
};
bootstrap();

Considering a request to /mypath, the logger output should be something like:

{"name":"RequestLogger","hostname":"HOSTNAME","pid":1,"level":30,"msg":"Before request GET '/mypath'","time":"2019-12-09T12:10:23.020Z","v":0}
{"name":"RequestLogger","hostname":"HOSTNAME","pid":1,"level":30,"msg":"After request GET '/mypath'","time":"2019-12-09T12:10:23.021Z","v":0}

doNotLogPaths

An array of base paths you do NOT want to log at all can be passed too.

app.use(RequestLogger.buildExpressRequestLogger({ doNotLogPaths: ['/health-server-status'] } as RequestLoggerOptions));

Then considering a request to /health-server-status, the logger will not log anything.

logOnlyBasePaths

An array of base paths you want to log without the full path (for security or GDPR reasons maybe) can be passed in the RequestLogger constructor.

app.use(RequestLogger.buildExpressRequestLogger({ logOnlyBasePaths: ['/my-path'] } as RequestLoggerOptions));

Then, considering a request to /my-path/[e-mail], the logger output should be something like:

{"name":"RequestLogger","hostname":"HOSTNAME","pid":1,"level":30,"msg":"Before request GET '/my-path'","time":"2019-12-09T12:10:23.020Z","v":0}
{"name":"RequestLogger","hostname":"HOSTNAME","pid":1,"level":30,"msg":"After request GET '/my-path'","time":"2019-12-09T12:10:23.021Z","v":0}

Logging Level

General Logging level can be changed centrally using environment property LOGGER_LEVEL. Possible values:

• fatal
• error
• warn
• info (default)
• debug
• trace

Pretty print

It's possible to pretty-print the logs by configuring environment property LOGGER_PRETTY_PRINT as 'true'.

This mode is NOT recommended for production environment.

Here's an example on how to do it:

LOGGER_PRETTY_PRINT=true npm run test

Then the console output would look like:

[2022-05-03T20:22:19.588Z]  INFO: MyPrettyLogger/22689 on MBP-van-Marcio: It works! (env=local)