n9-node-log

Logging node module based on Winston.

Requirements

• NodeJS >= 10.0.0

Installation

npm install --save @neo9/n9-node-log

Usage

import n9Log from '@neo9/n9-node-log';

const log = n9Log('my-app-name');

// Write on stdout
log.verbose('This is a verbose message');
log.debug('This is a debug message');
log.info('This is an information message');
log.warn('Warning, this feature will be removed soon');
// Write on stderr
log.error('An error appened');

2017-05-12T15:57:14.474Z - info: [my-app-name] This is an information message
2017-05-12T15:57:14.689Z - warn: [my-app-name] Warning, this feature will be removed soon
2017-05-12T15:57:14.974Z - error: [my-app-name] An error appened

Metadata

log.info('Log with metadata', { anything: 'this is metadata' });
log.error('Here an error', new Error('hello'));

2017-05-12T15:57:14.474Z - info: [my-app-name] Log with metadata anything=this is metadata
2017-05-12T15:57:14.785Z - error: [node-ts-skeleton] Here an error Error: hello
    at Object.<anonymous> (/home/schopin/Neo9/node-ts-skeleton/src/index.ts:16:28)
    at Module._compile (module.js:571:32)
    at ...

Prefixing

const logUsers = log.module('users');

logUsers.info('Log specific to users module');

2017-05-12T15:57:14.474Z - info: [my-app-name:users] Log specific to users module

Profiling

log.profile('test');
setTimeout(() => log.profile('test'), 1000);

2017-05-12T15:57:14.474Z - info: [my-app-name] test durationMs=1000

Log level

You can filter the list of logs on startup with the N9LOG environment or with the level option.

Possible values:

• verbose: Display all logs
• debug: Display debug + info + warn + error logs
• info: Display info + warn + error logs
• warn: Display warn + error logs
• error: Display only error logs

Default value: info

Example: N9LOG=error node server.js will display only error logs.

For performance matter, you can check if you need to compute your log data :

if (log.isLevelEnabled('debug')) {
    log.debug('My debug log', { complexDataAsOneField: JSON.stringify(data) });
}

Transports

Define the transporter(s) you want to use to store your logs, notice that you can combine them.

console

Will output the logs into process.stdout and process.stderr.

• Type: Boolean
• Default: true

Example:

const log = n9Log('my-app-name', {
    console: false, // Don't output the logs into the console
});

files

Will write the log output into specified file(s).

• Type: Array
• Default: []
• Properties:
  • level: Level of messages to write into the file (default: 'info')
  • filename: Path of the logfile
  • maxsize: Max sizes in bytes of the logfile
  • maxFiles: Limit the number of files created

Example:

const log = n9Log('my-app-name', {
    files: [
        {
            level: 'info',
            filename: '/tmp/info-log.log',
        },
    ],
});

http

• Type: Array
• Default: []
• Properties:
  • host: (Default: 'localhost') Remote host of the HTTP logging endpoint
  • port: (Default: 80 or 443) Remote port of the HTTP logging endpoint
  • path: (Default: '/') Remote URI of the HTTP logging endpoint
  • auth: (Default: None) An object representing the username and password for HTTP Basic Auth
  • ssl: (Default: false) Value indicating if we should us HTTPS

Example:

const log = n9Log('my-app-name', {
    http: [
        {
            host: 'my-logs.io',
            path: '/save',
            ssl: true,
        },
    ],
});

transports

Useful for adding custom transports into n9-node-log:

• Type: Array
• Default: []

Example:

import * as WinstonElasticSearch from 'winston-elasticsearch';

const log = n9Log('test', {
    console: false,
    transports: [
        new WinstonElasticSearch({
            index: 'n9-log',
            level: 'info',
            mappingTemplate: require('winston-elasticsearch/index-template-mapping.json'),
            flushInterval: 200,
        }),
    ],
});