A short presentation on how to log in your node.js application

1. Logging your Node.js
Application
Md. SOHEL RANA

2. About Me
• Founder, NerdDevs
• Software Architect, TestReach
• Node.js Trainer
• Working in Software Development for 12 years
• Last 6 years only working in JavaScript
• Loves backbone.js
http://www.nerddevs.com
twitter : @sohel023010
skype : sohel023010
https://github.com/sohel-rana

3. What is Logger
• A device or computer program
• Creates a systematic recording of events, observations, or measurements.
• Application, System, OS etc
• Helps to debug/trace issues

4. What is Logger
• Timestamp
• Source
• Event Type(error, info, debug etc)
• Message

5. What is Logger
Mac Console

6. Logger in node.js
• node-bunyan
• Morgan
• Winston
• Debug

7. bunyan
• Logs as JSON
const bunyan = require('bunyan’);
const log = bunyan.createLogger({name: 'myapp'});
log.info('hi’);
log.warn({lang: 'fr'}, 'au revoir’);
{"name":"myapp","hostname":"banana.local","pid":40161,"level":30,"msg":"hi","time":"201
3-01-04T18:46:23.851Z","v":0}

8. morgan
• Logs http request
// create a write stream (in append mode)
let accessLogStream = fs.createWriteStream(path.join(__dirname, 'access.log'), { flags: 'a’ });
// setup the logger
app.use(morgan('combined', { stream: accessLogStream }));
app.get('/', function (req, res) { res.send('hello, world!') })l

9. Winston
• Universal logger
• Supports multiple transports
• Supports ELK/EFK
• Two way to use, own logger or default

10. Winston
const getLoggerInstance = (level, logType) => {
return winston.createLogger({
format: winston.format.combine(
winston.format.label({ label: logType }),
winston.format.timestamp(),
customFormat
),
exitOnError: false,
transports: [
new FluentTransport(`testreach.${logType}`, _.extend(logConfig, {level})),
new winston.transports.DailyRotateFile({
level: level,
filename: `logs/%DATE%/${logType}.log`
})
]
});
};
An Example

11. Winston
winston.exceptions.handle(
new FluentTransport('testreach.unhandledExceptions', _.extend(logConfig,
{level: 'error'})),
new winston.transports.DailyRotateFile({
level: 'error',
filename: 'logs/%DATE%/unhandledExceptions.log'
})
);
Exception Handling

12. Winston
exports.logRequests = function (request, response) {
let userName = 'N/A';
if (request.user && request.user.username) {
userName = request.user.username;
}
if (request.xhr && request.method.trim() !== 'GET') {
if (request.body && JSON.stringify(request.body).indexOf('password') === -1) {
let allTexts = '';
if (userName) {
allTexts = `[ ${userName} ]- ${request.method}: ${request.url}`;
} else {
allTexts = `[ unknownUser ]- ${request.method}: ${request.url}`;
}
allTexts += `, Payload: ${JSON.stringify(request.body)}`;
loggerXhr.debug(allTexts);
}
}
};
Logger.js

13. Usage in application
const LoggerService = require('./services/Logger.js');
app.use(function (request, response, next) {
LoggerService.logRequests(request, response);
next();
});
app.js

14. Fluentd
• Unified logger
• Act as log collector
• Structures the data as JSON

15. Winston and Fluentd
• Use fluent-logger module
• Create a transport with tag
• Use that transport in Winston
let fluentTransport = require('fluent-
logger').support.winstonTransport();
let fluent = new fluentTransport('mytag', config);
let logger = winston.createLogger({ transports: [fluent, new
(winston.transports.Console)()] });
//Fleuntd config
<source>
@type forward port 24224
</source>
<match mytag.*>
@type stdout
</match>

16. Using EFK
Key points
• EFK – stands for Elasticsearch,
Fluentd and Kibana
• Elasticsearch stores the data in a
structured way and manages the
indexes for efficient searching
• Kibana a tool, helps to visualize the
data
Steps
• Create fluentd transport in winston
• Forward the logs to Elasticsearch
• Configure kibana to connect with
Elasticsearch
• Install necessary plugins

17. Kibana

18. Useful Practices
• Only log error from top level
• There is enough info
• Name the steps properly in debug

19. Useful Practices
• Error log
LoggerService.errorLog(error, req.user, ‘myController: User.save()’);
• Debug
Logger.loggerUserCall(`[Rejecting Incoming Call] ${JSON.stringify(requestData)}`);
Logger.loggerNumber(`[Buy number request] ${JSON.stringify(userNumberToBeSaved)}`);

20. Questions