simple-text-log

A Node.js package that provides simple text logging to a specified file. It has these features:

• Configurable -
  • Log file name and location
  • Maximum log file size
• No external dependencies
• Small footprint

Installation

npm install simple-text-log

Usage

The code shown below was derived from the code found in logtest.js and logtest2.js.

// get the module...
const Log = require('simple-text-log');
const logOut = new Log(require('./runlogopt.js'));

module.exports = {
    logfile:'./logs/logfile.log',
    // 10 MiB file size
    logsize:10485760
};

Note: The path ./logs/ must be created prior to writing any log entries.

There are two functions provided in Log, .writeTS() and .write(). The only difference is that .writeTS() will create a time stamp at the start of each log entry. And .write() does not. The time stamp looks like this -

[20210515-012455.739]: The rest of the log entry is here.

Here is some code that creates a common function that calls .writeTS() but adds the name of the file that the code is running in:

/*
    The following code inserts this file's name into
    the log message. It is not requried, but it makes
    it easier to trace the origin of the log messages.
*/
const path = require('path');
const scriptName = path.basename(__filename);
function log(payload) {
    logOut.writeTS(`${scriptName} - ${payload}`);
};

Here is an example of a log entry using the code above:

[20210515-012455.739]: logtest.js - test message 1

Found in logtest.js:

// start logging
log('*******************************************');
log(`begin app init`);
// create some log entries...
var testcount = 0;
log(`test message ${testcount += 1}`);
log(`test message ${testcount += 1}`);
log(`test message ${testcount += 1}`);
log(`test message ${testcount += 1}`);
log(`test message ${testcount += 1}`);

The log file will contain:

[20210515-012455.737]: logtest.js - *******************************************
[20210515-012455.739]: logtest.js - begin app init
[20210515-012455.739]: logtest.js - test message 1
[20210515-012455.739]: logtest.js - test message 2
[20210515-012455.740]: logtest.js - test message 3
[20210515-012455.740]: logtest.js - test message 4
[20210515-012455.740]: logtest.js - test message 5

Usage Recommendation

It is not necessary to require simple-text-log in every module within your application. If all of your modules' log entries are expected to be in the same log file then passing the log() function to each module.

Example:

Found in logtest.js:

/* ********************************************************
    Passing the logger function to other modules
*/
const tmp = require('./logtest2.js');
tmp(logOut);

logtest2.js:

module.exports = (function(logOut) {
    // set up run-time logging for this module,
    // this is not requried but it helps when
    // determining the origin of a log entry.
    const path = require('path');
    const scriptName = path.basename(__filename);
    function log(payload) {
        logOut.writeTS(`${scriptName} - ${payload}`);
    };

    log(`init 2`);

    // create some log entries...
    let testcount = 0;
    log(`test 2 message ${testcount += 1}`);
    log(`test 2 message ${testcount += 1}`);
    log(`test 2 message ${testcount += 1}`);
    log(`test 2 message ${testcount += 1}`);
    log(`test 2 message ${testcount += 1}`);
});

The log file will contain:

[20210515-012455.741]: logtest2.js - init 2
[20210515-012455.742]: logtest2.js - test 2 message 1
[20210515-012455.742]: logtest2.js - test 2 message 2
[20210515-012455.743]: logtest2.js - test 2 message 3
[20210515-012455.743]: logtest2.js - test 2 message 4
[20210515-012455.743]: logtest2.js - test 2 message 5

Log File Size Management

The maximum size of the active log file can be limited, or left unmanaged by changing the configuration. For example, if your configuration looks like this -

module.exports = {
    logfile:'./logs/logfile.log',
    // 10 MiB file size
    logsize:10485760
};

Then when ./logs/logfile.log exceeds the size set in logsize it will be renamed ./logs/logfile-YYYYMMDD-HHMMSS.log. A new ./logs/logfile.log will be created when the next log entry is written.

However, if logsize is 0 then the log file size is not managed and it will continue to grow. The size is only limited by your particular platform. This is not recommended in most usage scenarios.