simple-fs-rotator

NodeJS file stream rotator

Purpose

To provide an automated rotation of Express/Connect logs or anything else that writes to a file on a regular basis that needs to be rotated based on date, a size limit or combination and remove old log files based on count or elapsed days. This fork of File-Stream-Rotator adds an option to call a rotate async function at rotation time. No other rotation can occur until this promise does complete. During the promise run, logs are written in new current file. The current file size can therefore go higher than the max if the rotate function call takes too much time. This option is useful if you want to compress the file on rotation.

Install

npm install simple-fs-rotator

IMPORTANT NOTE

Since version 1, moment.js is not used anymore. The external dependencies have been removed. The date substitutions are done internally and only using numerical values for year, month, day, hour, minute, second. AM/PM is the only text replacement.

Frequency options have changed too.

Options

• filename: Filename including full path used by the stream
• frequency: How often to rotate. Options are 'daily' for daily rotation, 'date' based on date_format, '[1-12]h' to rotate every 1-12 hours, '[1-30]m' to rotate every 1-30 minutes.
• verbose: If set, it will use console.log to provide extra information when events happen. Default is false.
• date_format: Use 'Y' for full year, 'M' for month, 'D' for day, 'H' for hour, 'm' for minutes, 's' for seconds If using 'date' frequency, it is used to trigger file change when the string representation changes. It will be used to replace %DATE% in the filename. All replacements are numeric only.
• size: Max size of the file after which it will rotate. It can be combined with frequency or date format. The size units are 'k', 'm' and 'g'. Units need to directly follow a number e.g. 1g, 100m, 20k.
• max_logs Max number of logs to keep. The default is 10 files. It uses its own log audit file to keep track of the log files in a json format. It won't delete any file not contained in it. It can be a number of files or number of days. If using days, add 'd' as the suffix. e.g., '10d' for 10 days.
• audit_file Location to store the log audit file. If not set, it will be stored in the root of the application.
• end_stream End stream (true) instead of the default behaviour of destroy (false). Set value to true if when writing to the stream in a loop, if the application terminates or log rotates, data pending to be flushed might be lost.
• file_options An object passed to the stream. This can be used to specify flags, encoding, and mode. See https://nodejs.org/api/fs.html#fs_fs_createwritestream_path_options. Default { flags: 'a' }.
• utc Use UTC time for date in filename. Defaults to 'false'
• extension File extension to be appended to the filename. This is useful when using size restrictions as the rotation adds a count (1,2,3,4,...) at the end of the filename when the required size is met.
• create_symlink Create a tailable symlink to the current active log file. Defaults to 'FALSE'
• symlink_name Name to use when creating the symbolic link. Defaults to 'current.log'
• audit_hash_type Use specified hashing algorithm for audit. Defaults to 'md5'. Use 'sha256' for FIPS compliance.
• *rotate Async function to call at time of rotation. Function takes single parameter which is the name of the old file.

Example Usage

Typescript

import * as FileStreamRotator from 'file-stream-rotator'

var rotatingLogStream = FileStreamRotator.getStream({
    filename: "/tmp/test-%DATE%", 
    frequency: "daily", 
    date_format: "YYYY-MM-DD", 
    size: "100M",
    max_logs: "10",
    audit_file: "/tmp/audit.json",
    extension: ".log",
    create_symlink: true,
    symlink_name: "tail-current.log",
})

Javascript

// Default date added at the end of the file
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"daily", verbose: false});

// Default date added using file pattern
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test-%DATE%.log", frequency:"daily", verbose: false});

// Custom date added using file pattern using date format
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test-%DATE%.log", frequency:"daily", verbose: false, date_format: "YYYY-MM-DD"});

// Rotate when the date format is different (e.g monthly) using Y (Year), M (Month) replacements
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test-%DATE%.log", frequency:"custom", verbose: false, date_format: "YYYY-MM"});

// Rotate when the date format is different (e.g AM/PM) using Y (Year), M (Month), D (Day), A (AM/PM) replacements
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test-%DATE%.log", frequency:"custom", verbose: false, date_format: "YYYY-MM-DD-A"});

// Rotate on given minutes using the 'm' option i.e. 5m or 30m
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"5m", verbose: false});
  
// Rotate on the hour or any specified number of hours
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"1h", verbose: false});

// Rotate on the hour or any specified number of hours and keep 10 files
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"1h", verbose: false, max_logs: 10});

// Rotate on the hour or any specified number of hours and keep 10 days
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"1h", verbose: false, max_logs: "10d"});

// Rotate on the hour or any specified number of hours and keep 10 days and store the audit file in /tmp/log-audit.json
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/test.log", frequency:"1h", verbose: false, max_logs: "10d", audit_file: "/tmp/log-audit.json"});

// Rotate by file size only without date included in the name. Iteration will be added at the end.
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/logfile", size:"50k", max_logs: "5", audit_file:"/tmp/logaudit.json"});

// Rotate by file size only without date included in the name. Rotation added before the extension.
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/logfile", size:"50k", max_logs: "5", audit_file:"/tmp/logaudit.json", extension: ".log"});

// Rotate by file size only and compress.
var rotatingLogStream = require('file-stream-rotator').getStream({filename:"/tmp/logfile", size:"50k", max_logs: "5", rotate: async (oldFile) => compress(oldFile)});

//.....    

// Use new stream in express
app.use(express.logger({stream: rotatingLogStream, format: "default"}));

//.....

You can manually rotate the current open log to allow log archiving.

rotatingLogStream.rotate(true)

You can listen to the open, close, error and finish events generated by the open stream. You can also listen for custom events:

• rotate: that will pass two parameters to the callback: (oldFilename, newFilename)
• new: that will pass one parameter to the callback: newFilename
• logRemoved: that will pass one parameter to the callback: {date: unix_timestamp, name: filename_deleted, hash: log_file_unique_idenfifier}

You can also limit the size of each file by adding the size option using "k", "m" and "g" to specify the size of the file in kiloybytes, megabytes or gigabytes. When it rotates a file based on size, it will add a number to the end and increment it for every time the file rotates in the given period as shown below.

  3078  7 Mar 13:09:58 2017 testlog-2017-03-07.13.09.log.20
  2052  7 Mar 13:10:00 2017 testlog-2017-03-07.13.09.log.21
  3078  7 Mar 13:10:05 2017 testlog-2017-03-07.13.10.log.1
  3078  7 Mar 13:10:08 2017 testlog-2017-03-07.13.10.log.2
  3078  7 Mar 13:10:11 2017 testlog-2017-03-07.13.10.log.3
  3078  7 Mar 13:10:14 2017 testlog-2017-03-07.13.10.log.4

The example below will rotate files daily but each file will be limited to 5MB.

    // Rotate every day or every 5 megabytes, whatever comes first.
    var rotatingLogStream = require('file-stream-rotator').getStream(
        {
            filename:"/tmp/test-%DATE%.log", 
            frequency:"custom", 
            verbose: false, 
            date_format: "YYYY-MM-DD",
            size: "5M" // its letter denominating the size is case insensitive
        }
    );
    rotatingLogStream.on('rotate',function(oldFile,newFile){
        // do something with old file like compression or delete older than X days.
    })

NPM Maintainers

The npm module for this library will be maintained by:

• Roger C
• Ingo Fischer

Contributors

Thanks to the contributors below for raising PRs and everyone else that has raised issues to make the module better.

• Matt Berther
• nickbug
• André Farzat
• Thibault.P

License

file-stream-rotator is licensed under the MIT license.