fluent-logger for Node.js

fluent-logger implementation for Node.js inspired by fluent-logger-python.

Install

$ npm install fluent-logger

Prerequistes

Fluent daemon should listen on TCP port.

Simple configuration is following:

<source>
  @type forward
  port 24224
</source>

<match **.*>
  @type stdout
</match>

Usage

Send an event record to Fluentd

Singleton style

var logger = require('fluent-logger')
// The 2nd argument can be omitted. Here is a default value for options.
logger.configure('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});

// send an event record with 'tag.label'
logger.emit('label', {record: 'this is a log'});

Instance style

var logger = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});

The emit method has following signature

.emit([label string], <record object>, [timestamp number/date], [callback function])

Where only the record argument is required. If the label is set it will be appended to the configured tag.

Disable automatic reconnect

Both Singleton and Instance style can disable automatic reconnect allowing the user to handle reconnect himself

logger.configure('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   enableReconnect: false // defaults to true
});

Shared key authentication

Logger configuration:

var logger = require('fluent-logger').createFluentSender('dummy', {
  host: 'localhost',
  port: 24224,
  timeout: 3.0,
  reconnectInterval: 600000, // 10 minutes
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  }
});
logger.emit('debug', { message: 'This is a message' });

Server configuration:

<source>
  @type forward
  port 24224
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

See also Fluentd examples.

TLS/SSL encryption

Logger configuration:

var logger = require('fluent-logger').createFluentSender('dummy', {
  host: 'localhost',
  port: 24224,
  timeout: 3.0,
  reconnectInterval: 600000, // 10 minutes
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  },
  tls: true,
  tlsOptions: {
    ca: fs.readFileSync('/path/to/ca_cert.pem')
  }
});
logger.emit('debug', { message: 'This is a message' });

Server configuration:

<source>
  @type forward
  port 24224
  <transport tls>
    ca_cert_path /path/to/ca_cert.pem
    ca_private_key_path /path/to/ca_key.pem
    ca_private_key_passphrase very_secret_passphrase
  </transport>
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

FYI: You can generate certificates using fluent-ca-generate command since Fluentd 1.1.0.

See also How to enable TLS/SSL encryption.

Mutual TLS Authentication

Logger configuration:

var logger = require('fluent-logger').createFluentSender('dummy', {
  host: 'localhost',
  port: 24224,
  timeout: 3.0,
  reconnectInterval: 600000, // 10 minutes
  security: {
    clientHostname: "client.localdomain",
    sharedKey: "secure_communication_is_awesome"
  },
  tls: true,
  tlsOptions: {
    ca: fs.readFileSync('/path/to/ca_cert.pem'),
    cert: fs.readFileSync('/path/to/client-cert.pem'),
    key: fs.readFileSync('/path/to/client-key.pem'),
    passphrase: 'very-secret'
  }
});
logger.emit('debug', { message: 'This is a message' });

Server configuration:

<source>
  @type forward
  port 24224
  <transport tls>
    ca_path /path/to/ca-cert.pem
    cert_path /path/to/server-cert.pem
    private_key_path /path/to/server-key.pem
    private_key_passphrase very_secret_passphrase
    client_cert_auth true
  </transport>
  <security>
    self_hostname input.testing.local
    shared_key secure_communication_is_awesome
  </security>
</source>

<match dummy.*>
  @type stdout
</match>

EventTime support

We can also specify EventTime as timestamp.

var FluentLogger = require('fluent-logger');
var EventTime = FluentLogger.EventTime;
var logger = FluentLogger.createFluentSender('tag_prefix', {
var eventTime = new EventTime(1489547207, 745003500); // 2017-03-15 12:06:47 +0900
logger.emit('tag', { message: 'This is a message' }, eventTime);

Events

• connect : Handle net.Socket Event: connect
• error : Handle net.Socket Event: error

var logger = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});
logger.on('error', (error) => {
  console.log(error);
});
logger.on('connect', () => {
  console.log('connected!');
});

Logging Library Support

log4js

Use log4js-fluent-appender.

winston

Before using winston support, you should install it IN YOUR APPLICATION.

var winston = require('winston');
var config = {
  host: 'localhost',
  port: 24224,
  timeout: 3.0,
  requireAckResponse: true // Add this option to wait response from Fluentd certainly
};
var fluentTransport = require('fluent-logger').support.winstonTransport();
var fluent = new fluentTransport('mytag', config);
var logger = winston.createLogger({
  transports: [fluent, new (winston.transports.Console)()]
});

logger.on('flush', () => {
  console.log("flush");
})

logger.on('finish', () => {
  console.log("finish");
  fluent.sender.end("end", {}, () => {})
});

logger.log('info', 'this log record is sent to fluent daemon');
logger.info('this log record is sent to fluent daemon');
logger.info('end of log message');
logger.end();

NOTE If you use winston@2, you can use fluent-logger@2.7.0 or earlier. If you use winston@3, you can use fluent-logger@2.8 or later.

stream

Several libraries use stream as output.

'use strict';
const Console = require('console').Console;
var sender = require('fluent-logger').createFluentSender('tag_prefix', {
   host: 'localhost',
   port: 24224,
   timeout: 3.0,
   reconnectInterval: 600000 // 10 minutes
});
var logger = new Console(sender.toStream('stdout'), sender.toStream('stderr'));
logger.log('this log record is sent to fluent daemon');
setTimeout(()=> sender.end(), 5000);

Options

tag_prefix

The tag prefix string. You can specify null when you use FluentSender directly. In this case, you must specify label when you call emit.

host

The hostname. Default value = ‘localhost’.

See socket.connect

port

The port to listen to. Default value = 24224.

See socket.connect

path

The path to your Unix Domain Socket. If you set path then fluent-logger ignores host and port.

See socket.connect

timeout

Set the socket to timetout after timeout milliseconds of inactivity on the socket.

See socket.setTimeout

reconnectInterval

Set the reconnect interval in milliseconds. If error occurs then reconnect after this interval.

requireAckResponse

Change the protocol to at-least-once. The logger waits the ack from destination.

ackResponseTimeout

This option is used when requireAckResponse is true. The default is 190. This default value is based on popular tcp_syn_retries.

eventMode

Set Event Modes. This logger supports Message, PackedForward and CompressedPackedForward. Default is Message.

NOTE: We will change default to PackedForward and drop Message in next major release.

flushInterval

Set flush interval in milliseconds. This option has no effect in Message mode. The logger stores emitted events in buffer and flush events for each interval. Default 100.

messageQueueSizeLimit

Maximum number of messages that can be in queue at the same time. If a new message is received and it overflows the queue then the oldest message will be removed before adding the new item. This option has effect only in Message mode. No limit by default.

security.clientHostname

Set hostname of this logger. Use this value for hostname based authentication.

security.sharedKey

Shared key between client and server.

security.username

Set username for user based authentication. Default values is empty string.

security.password

Set password for user based authentication. Default values is empty string.

sendQueueSizeLimit

Queue size limit in bytes. This option has no effect in Message mode. Default is 8 MiB.

tls

Enable TLS for socket.

tlsOptions

Options to pass to tls.connect when tls is true.

For more details, see following documents

• tls.connect()
• tls.createSecureContext()

internalLogger

Set internal logger object for FluentLogger. Use console by default. This logger requires info and error method.

Examples

Winston Integration

An example of integrating with Winston can be found at ./example/winston.

You will need Docker Compose to run it. After navigating to ./example/winston, run docker-compose up and then node index.js. You should see the Docker logs having an "it works" message being output to FluentD.

License

Apache License, Version 2.0.

About NodeJS versions

This package is compatible with NodeJS versions >= 6.