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:

``aconf

@type forward
port 24224


*.>
@type stdout

`

Usage

$3

Singleton style

`js
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

`js
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

`js
.emit([label string], , [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.

$3


Both Singleton and Instance style can disable automatic reconnect allowing the user to handle reconnect himself
`js
logger.configure('tag_prefix', {
host: 'localhost',
port: 24224,
timeout: 3.0,
enableReconnect: false // defaults to true
});
`

$3

Logger configuration:

`js
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:

`aconf

@type forward
port 24224

self_hostname input.testing.local
shared_key secure_communication_is_awesome




@type stdout

`

See also Fluentd examples.

$3

Logger configuration:

`js
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:

`aconf

@type forward
port 24224

ca_cert_path /path/to/ca_cert.pem
ca_private_key_path /path/to/ca_key.pem
ca_private_key_passphrase very_secret_passphrase


self_hostname input.testing.local
shared_key secure_communication_is_awesome




@type stdout

`

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

See also How to enable TLS/SSL encryption.

$3

Logger configuration:

`js
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:

`aconf

@type forward
port 24224

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


self_hostname input.testing.local
shared_key secure_communication_is_awesome




@type stdout

`

$3

We can also specify EventTime as timestamp.

`js
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);
`

$3

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

`js
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

$3

Use log4js-fluent-appender.

$3

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

`js
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.

$3

Several libraries use stream as output.

`js
'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][1]

port

The port to listen to. Default value = 24224.

See [socket.connect][1]

path

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

See [socket.connect][1]

timeout

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

See [socket.setTimeout][2]

reconnectInterval

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

[1]: https://nodejs.org/api/net.html#net_socket_connect_path_connectlistener
[2]: https://nodejs.org/api/net.html#net_socket_settimeout_timeout_callback

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

$3

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.

[fluent-logger-python]: https://github.com/fluent/fluent-logger-python

About NodeJS versions

This package is compatible with NodeJS versions >= 6.