als-performance-monitor

The als-performance-monitor module offers an efficient performance monitoring tool tailored for Node.js applications. It encompasses a versatile suite of modules that track and oversee system-level performance metrics including CPU usage, RAM, RSS, and Swap memory.

Installation

npm install als-performance-monitor

Quick Start

To get started with als-performance-monitor, follow the example below:

const PM = require('als-performance-monitor');

const preferences = {
   cpu: 0.8,           // Monitor CPU, set max threshold at 80%
   ram: 0.7,           // Monitor RAM, set max threshold at 70%
   rss: 500,           // Monitor RSS, set max threshold at 500MB
   swap: 0.5,          // Monitor Swap, set max threshold at 50% (checked once per minute)
   timesInMinute: 60,  // Specify frequency of checks and logs per minute
   errorThreshold: 20  // Reset pm.errors after this number of unique errors
};

const pm = new PM(preferences);

// Registering Events
pm.emitter.on('overload', () => console.log('Overloaded event'));  // Triggered when overloaded (only when watching)
pm.emitter.on('backToNormal', () => console.log('Back to normal event'));  // Triggered when returning to normal state (only when watching)
pm.emitter.on('next', logs => console.log(logs));  // Invoked on every measurement
pm.emitter.on('error', (error, pmObj) => {  // Invoked on every unique error occurrence
   console.error(error.message);
   if (pmObj.errors.length > 20) pmObj.stop();
});

pm.run();      // Start the monitor
pm.watch();    // Start the monitor with overload tracking (enables related events)

// Check if any module is overloaded
if (pm.overloaded()) {
   console.log('System Overloaded');
}

pm.stop();   // Stops the monitor
pm.avg();    // Returns average values for the last set duration
pm.errors;   // Retrieves the last 20 errors for all modules

Note: The overloaded method determines overload based on averages, not current performance values.

Note: pm.emitter is an instance of als-event-emitter and supports methods like: on, off, has, once, etc.

Using Hooks

Providing both onOverload and onBackToNormal hooks as parameters prompts the monitor to check for overload at each interval. It will invoke the onOverload function upon detecting an overload and the onBackToNormal function once it returns to a normal state.