Log

Introduced in 1.0.0

Stability: 2 - Stable

const Log = require('kado/lib/Log')

This library provides logging abstraction to use different log transports for system level log messages.

Class: Log

Log extends ConnectEngine see ConnectEngine for engine management and more.

This is the log multiplexer to hold engines such as the LogEngine.

It only exposes ConnectEngine methods.

Class: LogEngine

Log extends Connect see Connect for more engine management and more.

static LogEngine.appendFile(path, data)

• path {string} the path of the file to append text to
• data {string} the data to append to the file
• Return {string} the data appended to the file

static LogEngine.tailFile(path, lineCount, options)

• path {string} the path to the file to tail
• lineCount {number} number of lines to take from the file.
• options {Object} options passed to FileByLine, see below.
• Return {string} last n lines from the specified file.

static LogEngine.getInstance()

• Return {Log} new instance of the logger system

LogEngine._read ()

Underlying stream read method for Stream.readable.

Internal Use

LogEngine.getDate(now)

• now {Date} the current date.
• Return {String} date string to add to the log message

Internal Use

LogEngine.message (level, msg, opts)

• level {Object} the level of severity for the message
• msg {String} the message to print
• opts {Object} options to control messaging
• Return {void}

Pushes the newly formed message into the stream.

Internal Use

LogEngine.error (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.warning (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.info (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.verbose (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.debug (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.extra (msg, opts)

• msg {String} message to print
• opts {Object} options to control messaging
• Return {void}

Makes use of the Log.message method to send the log message.

LogEngine.dump (msg)

• msg {Mixed} message to print
• Return {void}

Makes use of the Log.message method to send the log message.

This method does not wrap the message with any status information.

LogEngine.constructor()

• Return {Log} new instance of the logger

Class LogRelayUDP extends Stream.Writable

Relay log messages from any LogEngine using UDP.

Example Usage

// add our logger
const log = Log.LogEngine.getInstance({ name: pkg.name })
const logRelay = new Log.LogRelayUDP()
log.pipe(logRelay)
app.log.addEngine('console', log)

Example Log Receiver (this is a standalone program)

'use strict'
const dgram = require('dgram')
const server = dgram.createSocket('udp4')
server.on('error', (err) => { console.log(err) })
server.on('message', (msg) => { process.stdout.write(msg) })
server.on('listening', () => { console.log('Ready for Log Messages') })
server.bind('5514')

Log messages are send on UDP over port 5514. They are plain text.

Please consider transport layer encryption or keeping messages on a layer 2 networks to avoid security concerns.

LogRelayUDP.constructor(options)

• options {Object} options to control the relay.
• Return {LogRelayUDP} new instance.

Available Options

• host {string} host to send messages to, default localhost
• port {string} port to send messages to, default 5514
• protocol {string} IP protocol of the transport default udp4

Since LogRelayUDP is a Stream.Writable instance and LogEngine is a Stream.Readable instance. Use the log relay by piping the engine into the relay prior to passing the engine into the log multiplexer.

Example

log.pipe(new Log.LogRelayUDP({ host: 'some-machine' }))

Class FileByLine

Based on: https://github.com/nacholibre/node-readlines

Read a file by lines.

FileByLine.constructor(options)

• options {Object} options to control the file processing.
• Return {FileByLine} new instance

Available Options

• readChunk {number} size of the read buffer in bytes
• newLineCharacter {string} which type of newline to use, defaults to \n

FileByLine.next()

• Return {string} next line of the file until EOF which returns null

Example Usage

const fd = new FileByLine(path, options)
let line; const lines = []
while ((line = fd.next())) lines.push(line)