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@dengue8830 dengue8830/logger.ts
Created Dec 20, 2018

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Logger wrapper for nodejs
import * as winston from 'winston';
import * as moment from 'moment';
const customLevels = {
levels: {
trace: 5,
debug: 4,
info: 3,
warn: 2,
error: 1,
fatal: 0
},
colors: {
trace: 'white',
debug: 'green',
info: 'green',
warn: 'yellow',
error: 'red',
fatal: 'red'
}
};
const isProductionEnv = process.env.NODE_ENV === 'production';
const parser = (param: any): string => {
if (!param) {
return '';
}
if (typeof param === 'string') {
return param;
}
return Object.keys(param).length ? JSON.stringify(param, undefined, 2) : '';
};
const formatter = winston.format.combine(
winston.format.colorize(),
winston.format.timestamp(),
winston.format.splat(),
winston.format.printf((info) => {
const { timestamp, level, message, meta } = info;
const ts = moment(timestamp).local().format('HH:MM:ss');
const metaMsg = meta ? `: ${parser(meta)}` : '';
return `${ts} [${level}] ${parser(message)} ${metaMsg}`;
}),
);
/**
* This class Takes care of the logs on the app.
*
* For both prod and dev environments we use Console transport because we use
* pm2 for production and it handles the console logs quite fine. If you are not using pm2
* you can use a File transport for production.
*
* Our pm2 start.json is configured with a single out.log file for all the log types in order to get
* a simpler configuration. If you need a separate file for errors for pm2, edit start.json and set a
* different file name for error, later edit error method of this class and use the simple console.error,
* pm2 will handle it and print it in the error file described in start.json.
*/
class Logger {
private logger: winston.Logger;
constructor() {
// Use this config for separate transport for prod if you are not using pm2
// const prodTransport = new winston.transports.File({ filename: 'logs/error.log', level: 'error' });
const transport = new winston.transports.Console({
// format: winston.format.combine(winston.format.colorize(), winston.format.simple()),
format: formatter
});
this.logger = winston.createLogger({
// Logs error and fatal for prod and the rest for dev
level: isProductionEnv ? 'error' : 'trace',
// We redefine security leves as mentioned
levels: customLevels.levels,
transports: [transport]
});
winston.addColors(customLevels.colors);
}
trace(msg: any, meta?: any) {
this.logger.log('trace', msg, meta);
}
debug(msg: any, meta?: any) {
this.logger.debug(msg, meta);
}
info(msg: any, meta?: any) {
this.logger.info(msg, meta);
}
warn(msg: any, meta?: any) {
this.logger.warn(msg, meta);
}
error(msg: any, meta?: any) {
this.logger.error(msg, meta);
// Use this way to make pm2 put the error log in the error file
// Set the name of the error file in start.json
// TODO: extract the printf function to reuse the code
// console.error(msg, meta);
}
fatal(msg: any, meta?: any) {
this.logger.log('fatal', msg, meta);
}
}
/**
* Examples
*/
// logger.trace({ x: 2 }, { a: 1 });
// logger.trace('hi', { a: 1 });
// logger.trace({ x: 2 }, 'by');
// logger.trace('hi again');
// logger.trace('that its', 'by');
export const logger = new Logger();
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