In this blog post, we are going to take a look at how to create a well-structured log system in Node JS using Express JS, Morgan, and Winston.
I was looking for a robust logging system for a crypto dashboard API that I built one month ago and I found this article: https://levelup.gitconnected.com/better-logs-for-expressjs-using-winston-and-morgan-with-typescript-1c31c1ab9342 very useful. The sample made in the article is TypeScript based. So, if you're trying to use TypeScript
instead of Js
, you don't need to continue reading the current post, just check out the link. In my crypto project, I hadn't used TypeScript, that's why I am writing this blog post.
To follow along with this article, you will need:
express-morgan-winston
for your projectnpm init
commandexpress
, morgan,
and winston
as dependenciesnpm init
command: app.js
in my case). This is where you will handle the main logic in your Express servermkdir express-morgan-winston
cd express-morgan-winston
npm init
npm install morgan winston --save
touch src/app.js # or mdkdir src && echo "" > src/app.js
Basically, we need to define :
Create a file src/utils/logger.js
and copy-paste the code below. All parts of the configuration are well explained.
const winston = require('winston');
// Define your severity levels.
// With them, You can create log files,
// see or hide levels based on the running ENV.
const levels = {
error: 0,
warn: 1,
info: 2,
http: 3,
debug: 4,
}
// This method set the current severity based on
// the current NODE_ENV: show all the log levels
// if the server was run in development mode; otherwise,
// if it was run in production, show only warn and error messages.
const level = () => {
const env = process.env.NODE_ENV || 'development'
const isDevelopment = env === 'development'
return isDevelopment ? 'debug' : 'warn'
}
// Define different colors for each level.
// Colors make the log message more visible,
// adding the ability to focus or ignore messages.
const colors = {
error: 'red',
warn: 'yellow',
info: 'green',
http: 'magenta',
debug: 'white',
}
// Tell winston that you want to link the colors
// defined above to the severity levels.
winston.addColors(colors)
// Chose the aspect of your log customizing the log format.
const format = winston.format.combine(
// Add the message timestamp with the preferred format
winston.format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss:ms' }),
// Tell Winston that the logs must be colored
winston.format.colorize({ all: true }),
// Define the format of the message showing the timestamp, the level and the message
winston.format.printf(
(info) => `${info.timestamp} ${info.level}: ${info.message}`,
),
)
// Define which transports the logger must use to print out messages.
// In this example, we are using three different transports
const transports = [
// Allow the use the console to print the messages
new winston.transports.Console(),
// Allow to print all the error level messages inside the error.log file
new winston.transports.File({
filename: 'logs/error.log',
level: 'error',
}),
// Allow to print all the error message inside the all.log file
// (also the error log that are also printed inside the error.log(
new winston.transports.File({ filename: 'logs/all.log' }),
]
// Create the logger instance that has to be exported
// and used to log messages.
const logger = winston.createLogger({
level: level(),
levels,
format,
transports,
})
module.exports = logger
We have a logger utility file that is ready for use anywhere in our express app. Now let's configure Morgan.
The configuration we need to make here is very simple:
So I created the file src/middlewares/morgan.middleware.js
and add the following code:
const morgan = require("morgan");
const logger = require("../utils/logger");
const stream = {
// Use the http severity
write: (message) => logger.http(message),
};
const skip = () => {
const env = process.env.NODE_ENV || "development";
return env !== "development";
};
const morganMiddleware = morgan(
// Define message format string (this is the default one).
// The message format is made from tokens, and each token is
// defined inside the Morgan library.
// You can create your custom token to show what do you want from a request.
":remote-addr :method :url :status :res[content-length] - :response-time ms",
// Options: in this case, I overwrote the stream and the skip logic.
// See the methods above.
{ stream, skip }
);
module.exports = morganMiddleware;
const express = require("express");
const morganMiddleware = require("./middlewares/morgan.middleware");
// The morgan middleware does not need this.
// This is for a manual log
const logger = require("./utils/logger");
const app = express();
// Add the morgan middleware
app.use(morganMiddleware);
app.get("/api/status", (req, res) => {
logger.info("Checking the API status: Everything is OK");
res.status(200).send({
status: "UP",
message: "The API is up and running!"
});
});
// Startup
app.listen(3000, () => {
logger.info('Server is running on port 3000');
});
Run the app using the command node src/app.js
and call the API status endpoint. Below is how my terminal looks like:
You can notice that a log file named logs/all.log
was automatically generated and contains all log messages.
Our final project structure looks like below:
📘express-morgan-winston/
┣ 📁logs/
┃ ┣ ✨all.log
┃ ┗ ✨error.log
┣ 📁src/
┃ ┣ 📁middlewares/
┃ ┃ ┗ ✨morgan.middleware.js
┃ ┣ 📁utils/
┃ ┃ ┗ ✨logger.js
┃ ┗ ✨app.js
┣ ✨package-lock.json
┗ ✨package.json
Check out the source code on my GitHub organization Lioncoding-oss.
If you find this blog post useful, please share it on your favorite social media. Don't forget to follow me on GitHub and Twitter. To send me a message, please use the contact form or DM me on Twitter.
Quick Links