How can i use custom logger in fastify? - node.js

Question

My company have a custom developed logger package, and we want to use that as default logger in fastify. I tried to understand how to register my logger with this simple example below, but fastify always use Pino.
index.js
const log = require("./Logger");
const fastify = require("fastify")({ logger: log });
fastify.get("/", (request, reply) => {
request.log(
"includes request information, but is the same logger instance as `log`"
);
reply.send({ hello: "world" });
});
fastify.listen(3000)
logger.js
function Logger(...args) {
this.args = args;
}
Logger.prototype.info = function(msg) {
console.log("myLogger", msg);
};
logger.js also contains error, debug, fatal, warn, trace, child functions but the functions body is same.
The result is:
{"level":30,"time":1553095994942,"msg":"Server listening at http://127.0.0.1:3000","pid":14543,"hostname":"VirtualBox","v":1}
whitch is the default Pino output.

Answer 1

as explained here, your logger
must have the following methods
So this example works:
function Logger(...args) {
this.args = args;
}
Logger.prototype.info = function (msg) { console.log("myLogger", msg); };
Logger.prototype.error = function (msg) { console.log("myLogger", msg); };
Logger.prototype.debug = function (msg) { console.log("myLogger", msg); };
Logger.prototype.fatal = function (msg) { console.log("myLogger", msg); };
Logger.prototype.warn = function (msg) { console.log("myLogger", msg); };
Logger.prototype.trace = function (msg) { console.log("myLogger", msg); };
Logger.prototype.child = function () { return new Logger() };
const myLogger = new Logger()
const app = require('fastify')({
logger: myLogger
})
app.get("/", (request, reply) => {
request.log.info('hi');
reply.send({ hello: "world" });
});
app.listen(3000)
Here you can check the logger validation applied to your parameter

Answer 2

in case you need log4js,
this is a customized logger that supports json event.
you c
import log4js from "log4js";
import {log4jsConfig} from "./log4js.config.js";
log4js.addLayout('json', function (config) {
return function (logEvent) {
logEvent.application = 'my-app';
logEvent.processId = process.pid;
if (process.env.IP) {
logEvent.ip = process.env.IP;
}
if (process.env.ENV) {
logEvent.ENV = process.env.ENV;
}
if (logEvent.data && logEvent.data.length > 0) {
logEvent.message = logEvent.data[0];
delete logEvent.data;
}
return JSON.stringify(logEvent);
};
});
const log = log4js.getLogger('engine');
log4js.configure(log4jsConfig);
export class AndromedaLogger {
logger;
loggerOptions;
constructor(args) {
this.logger = log;
}
get Logger() {
return this.logger;
}
static configGlobal(options) {
this.loggerOptions = options;
}
info(message) {
this.logger.info(message);
}
error(message, trace) {
this.logger.error(`${message} -> (${trace || 'trace not provided !'})`);
}
warn(message) {
this.logger.warn(message);
}
debug(message, context) {
this.logger.debug(message);
}
trace(message, context) {
this.logger.trace(message);
}
fatal(message, context) {
this.logger.fatal(message);
}
child() {
return new AndromedaLogger()
};
}
log4js config:
const _log4jsConfig = {
appenders: {},
categories: {
default: {
appenders: [],
level: 'trace',
},
},
};
_log4jsConfig.appenders.stdout = {
type: 'stdout',
layout: { type: 'colored' },
};
_log4jsConfig.appenders['file'] = {
type: 'file',
filename: 'logs/app.log',
maxLogSize: 104857600,
numBackups: 3,
};
_log4jsConfig.categories.default.appenders.push('stdout');
_log4jsConfig.categories.default.appenders.push('file');
export const log4jsConfig = _log4jsConfig;