how to capture nestjs bootstrap errors in a log file - node.js

Question

I'm trying to capture all logs(bootstrap, app error messages, db connection error messages) into a single log file in nestjs.
As of now I'm using a custom logger to so. Below is my custom logger code
logger.ts
import * as winston from 'winston';
import * as chalk from 'chalk';
import PrettyError from 'pretty-error';
import { LoggerOptions } from 'winston';
export class LoggerService {
private readonly logger: winston.Logger;
private readonly prettyError = new PrettyError();
public static loggerOptions: LoggerOptions = {
transports: [
new winston.transports.File({
filename: 'logs/mgmtserver-main.log',
format: winston.format.json()
}),
],
};
constructor(private context: string, transport?) {
this.logger = (winston as any).createLogger(LoggerService.loggerOptions);
this.prettyError.skipNodeFiles();
this.prettyError.skipPackage('express', '#nestjs/common', '#nestjs/core');
}
get Logger(): winston.Logger {
return this.logger;
}
static configGlobal(options?: LoggerOptions) {
this.loggerOptions = options;
}
log(message: string): void {
const currentDate = new Date();
this.logger.info(message, {
timestamp: currentDate.toISOString(),
context: this.context,
});
this.formatedLog('info', message);
}
error(message: string, trace?: any): void {
const currentDate = new Date();
this.logger.error(`${message} -> (${trace || 'trace not provided !'})`, {
timestamp: currentDate.toISOString(),
context: this.context,
});
this.formatedLog('error', message, trace);
}
warn(message: string): void {
const currentDate = new Date();
this.logger.warn(message, {
timestamp: currentDate.toISOString(),
context: this.context,
});
this.formatedLog('warn', message);
}
overrideOptions(options: LoggerOptions) {
this.logger.configure(options);
}
// this method just for printing a cool log in your terminal , using chalk
private formatedLog(level: string, message: string, error?): void {
let result = '';
const color = chalk.default;
const currentDate = new Date();
const time = `${currentDate.getHours()}:${currentDate.getMinutes()}:${currentDate.getSeconds()}`;
switch (level) {
case 'info':
result = `[${color.blue('INFO')}] ${color.dim.yellow.bold.underline(time)} [${color.green(
this.context,
)}] ${message}`;
break;
case 'error':
result = `[${color.red('ERR')}] ${color.dim.yellow.bold.underline(time)} [${color.green(
this.context,
)}] ${message}`;
break;
case 'warn':
result = `[${color.yellow('WARN')}] ${color.dim.yellow.bold.underline(time)} [${color.green(
this.context,
)}] ${message}`;
break;
default:
break;
}
console.log(result);
}
}
I'm able to log application erro messages(err, warn, info) using the above logger in any file like below
import { LoggerService } from 'logger';
private readonly logger: LoggerService = new LoggerService(RegistrationService.name);
this.logger.warn('this is a warn message');
my main.ts looks like below
import { ValidationPipe, Logger } from "#nestjs/common";
import { NestFactory } from "#nestjs/core";
import { ConfigService } from '#nestjs/config';
import { AppModule } from "./app.module";
import { WinstonModule } from 'nest-winston';
import * as winston from 'winston';
import { LoggerService } from "logger";
async function bootstrap() {
const app = await NestFactory.create(AppModule, {
logger: new LoggerService('Main'), abortOnError: false
});
app.enableCors();
await app.listen(3000);
console.log(`Application is running on: ${await app.getUrl()}`);
}
bootstrap();
The issue is I'm not able to capture the Nestfactory.create. bootstrap errors in the log file. They are getting printed on the console but not to log file.
For example, the below bootstrap errors are getting printed on console but not into the log file.
[INFO] 15:12:50 [Main] Starting Nest application...
[ERR] 15:12:50 [Main] Nest cannot create the AuthorisationModule instance.
The module at index [3] of the AuthorisationModule "imports" array is undefined.
Potential causes:
- A circular dependency between modules. Use forwardRef() to avoid it. Read more: https://docs.nestjs.com/fundamentals/circular-dependency
- The module at index [3] is of type "undefined". Check your import statements and the type of the module.
Please help me. Your help is much appreciated.

Answer 1

That is because your logger module isn't initialized until Nest finishes initializing the App context. Your logger will capture all the errors after the your App is running but not before.
However you can make use of node's inbuilt events to log/file these exceptions
process.on('uncaughtException', err => {
console.error('There was an uncaught error', err)
process.exit(1) //mandatory (as per the Node.js docs)
})
or, for Promises,
process.on('unhandledRejection', err => {
console.error('There was an uncaught error', err)
process.exit(1) //mandatory (as per the Node.js docs)
})
https://nodejs.dev/learn/error-handling-in-nodejs#catching-uncaught-exceptions