scarlet-contrib-logger

Scarlet plugin for a simple logger

Install

npm install scarlet-contrib-logger

Start logging

var Scarlet = require('scarlet');
var scarlet = new Scarlet('../lib/scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;
 
//Attach Logger to object
scarletLogger.bindTo(Math,'min');
 
//Now use intercepted object with logging!
Math.min(1,2,3);
//->[Mon Sep 02 2013 01:07:05 GMT+0100 (BST)] - Debug - calling - Object::min(1,2,3)
//->[Mon Sep 02 2013 01:07:05 GMT+0100 (BST)] - Debug - Object::min(1,2,3) - returned:1 - execution time(0:0:0.0)

Getting Started

This plugin requires Scarlet ~0.5.x

If you haven't used Scarlet before, be sure to check out the Documentation. To use this plugin perform the following:

Install scarlet

npm install scarlet --save

Install plugin

npm install scarlet-contrib-logger --save

Once the plugin has been installed, you can use it in your application as follows:

//load scarlet
var Scarlet = require('scarlet');
 
//Initialize scarlet with the plugin
var scarlet = new Scarlet('scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;

Project Purpose

This project uses Scarlet to show how logging and interception can be easily integrated into your project.

Instead of having to write code that mixes in logging and application logic like this:

function FunctionToLog(){
    this.function1 = function(){
      console.log("called function1");
      //do important stuff
      console.log("completed function1 - returned:"+someReturnValue);
  }
}

Using scarlet logger you can attach every instance of a function to the logger, and get rid of extra logging code.

var Scarlet = require('scarlet');
var scarlet = new Scarlet('scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;
 
function FunctionToLog(){
    this.function1 = function(){
      //do important stuff
  }
}
//Attach the logger to the function
FunctionToLog = scarletLogger.bindTo(FunctionToLog);
//-> now any instances of FunctionToLog will log.

This can also be helpful in debugging where you just want to find out what is getting called when. Just attach the logger to an instance like so:

scarletLogger.bindTo(someInstance);
someInstance.someFunction();
////-> someFunction will now be logged, along with subsequent calls to methods on *someinstance*

Scarlet is a javascript interceptor that allows access to important information about methods, object names, method names. In addtion, it allows Scarlet Logger get access to a method before and after it is called.

Using Your own appender

Scarlet logger uses a console appender as default to use a different appender just do the following when initializing scarlet logger:

scarletLogger.appender(customAppender).bindTo(someInstance);

by calling the appender method with your custom appender the logger will use that instead of the default console appender.

A custom appender must have a append method. Here is an example as follows:

var CustomAppender = module.exports = exports =  function(){};
 
CustomAppender.prototype.append = function(message){
  //do something custom with log message
};

Using Your own Log Interceptor

Scarlet logger uses a log interceptor that logs specfic details; execution time, function names, etc. If you want to use your own log interceptor do the following:

scarletLogger.interceptor(customInterceptor).bindTo(someInstance);

by calling the interceptor method with your custom interceptor the logger will use that when intercepting methods.

A custom interceptor must be a Scarlet interceptor. Here is an example of a simple custom interceptor:

var customInterceptor = function(proceed, invocation){
  console.log("Before Method:"+invocation.methodName+" called");
  proceed();
  console.log("After Method:"+invocation.methodName+" called");
}

The above doesn't use an appender and is a very basic interceptor.

Examples

Start logging a single instance

//Init ScarletLogger
var Scarlet = require('scarlet');
var scarlet = new Scarlet('scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;
 
//Define a function to log
function FunctionToLog(){
 this.logMe = function(){ console.log("In logMe"); }
};
var functionToLogInstance = new FunctionToLog();
 
//Attach Logger to object
scarletLogger.bindTo(functionToLogInstance);
 
//Now use intercepted object with logging!
functionToLogInstance.logMe();
//-> Outputs the following to the console:
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - calling - FunctionToLog::logMe()
//->In logMe
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - FunctionToLog::logMe() - returned:undefined - execution time(0:0:0.0)

Start logging all instances of a function

//Init ScarletLogger
var Scarlet = require('scarlet');
var scarlet = new Scarlet('scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;
 
function FunctionToLog(){
 this.logMe = function(){ console.log("In logMe"); }
};
 
//Attach Logger to object
FunctionToLog = scarletLogger.bindTo(FunctionToLog);
 
//Now use intercepted object with logging!
var functionToLogInstance = new FunctionToLog();
//-> Outputs the following to the console:
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - calling - FunctionToLog::FunctionToLog()
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - FunctionToLog::FunctionToLog() - returned:undefined - execution time(0:0:0.0)
 
functionToLogInstance.logMe();
//-> Outputs the following to the console:
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - calling - FunctionToLog::logMe()
//->In logMe
//->[Tue Aug 27 2013 09:39:55 GMT+0100 (BST)] - Debug - FunctionToLog::logMe() - returned:undefined - execution time(0:0:0.0)

Start logging all instances of a prototype function

//Init ScarletLogger
var Scarlet = require('scarlet');
var scarlet = new Scarlet('scarlet-contrib-logger');
var scarletLogger = scarlet.plugins.logger;
 
//Define an prototype object to log
var ObjectToLog = function (){};
ObjectToLog.prototype.someMethod = function(){return 1;};
 
//Attach Logger to object
ObjectToLog = scarletLogger.bindTo(ObjectToLog);
 
//Now use intercepted object 
var objectToLog = new ObjectToLog();
//-> Outputs the following to the console:
//->[Tue Aug 27 2013 09:50:23 GMT+0100 (BST)] - Debug - calling - FunctionToLog::FunctionToLog()
//-?[Tue Aug 27 2013 09:50:23 GMT+0100 (BST)] - Debug - FunctionToLog::FunctionToLog() - returned:undefined - execution time(0:0:0.1)
 
//When called will now get logged
var result = objectToLog.someMethod();
//-> Outputs the following to the console:
//->[Tue Aug 27 2013 09:50:23 GMT+0100 (BST)] - Debug - calling - FunctionToLog::logMe()
//->In logMe
//->[Tue Aug 27 2013 09:50:23 GMT+0100 (BST)] - Debug - FunctionToLog::logMe() - returned:undefined - execution time(0:0:0.0)