Winston logger to log to two files - node.js

Question

I have two different winston loggers which look like this (there are two separate ones as they write different logs depending on my functions) - :
var security = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
})
]
});
And then I have one more for :
var system = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
})
]
});
However, I also have a verbose.log file, where I want all of the logs from the security and system log file to be written to the verbose too. Whats the best way of doing that?
I tried adding the filename (i.e. verbose.log) to each of the transports, but this does not work as I get the error
Error: Transport already attached: dailyRotateFile, assign a different name

Answer 1

It is a common problem with winston, but a simple one to solve.
Due to how winston is coded, it cannot differenciate your two transport himself, and need you to explicitly declare them as separate by giving them different names:
var security = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
//=>
name: 'foo',
//<=
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
})
]
});
var system = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
//=>
name: 'bar',
//<=
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
})
]
});
The name itself doesn't matter as long as it is different, a easy way to do that is to use the filename along with some other identifier for the transport.
Source: issue #101 of the official Github
EDIT:
var verbose = new(require('winston-daily-rotate-file'))({
name: 'baz',
filename: logDir + '/-verbose.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
})
var security = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
//=>
name: 'foo',
//<=
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
}),
//=>
verbose
//<=
]
});
var system = new(winston.Logger)({
transports: [
new(require('winston-daily-rotate-file'))({
//=>
name: 'bar',
//<=
filename: logDir + '/-security.log',
datePattern: 'dd-MM-yyyy',
prepend: true,
json: false,
timestamp: function() {
return moment().format('D/MM/YYYY HH:mm:ss:SSS');
}
}),
//=>
verbose
//<=
]
});

Answer 2

You can filter out logs by creating two or more loggers as per your requirement and adding name property to them. Adding a common transport function in both logger worked for me.
const winston = require('winston');
const combinedLogger = new winston.transports.File({
name: "data",
filename: "./logs/combined.log",
level: "info",
})
const infoLogger = winston.createLogger({
defaultMeta: { service: "log-service" },
transports: [
new winston.transports.File({
name: "info",
filename: "./logs/info.log",
level: "info",
}),
combinedLogger
],
});
const errorLogger = winston.createLogger({
defaultMeta: { service: "log-service" },
transports: [
new winston.transports.File({
name: "error",
filename: "./logs/error.log",
level: "error",
}),
combinedLogger
],
});
const logger = {
info: (params) => {
return infoLogger.info(params);
},
error: (params) => {
return errorLogger.error(params);
},
};
logger.info("info log"); // Will goto info.log & combined.log
logger.error("error log"); // Will goto error.log & combined.log