unity-ngo-hostmigration/statistics.js

var os = require('os');

(function () {
    // vars
    stats_data = {};
    stats_request_ip_list = [];
    stats_request_count = 0;
    stats_hw_cpu_last = 0;
    stats_hw_ram_last = 0;
    // methods 
    stats_start = function() {
        setInterval( () => {
            // get cpu results for next tick 
            stats_cpuUsage( ( cpu_perc ) => 
            {
                var ram_total = os.totalmem();
                var ram_free = os.freemem();
                stats_hw_cpu_last = cpu_perc;
                stats_hw_ram_last = ( ram_total - ram_free ) / ram_total;
            } );
            // save state 
            stats_data = {
                time : Date.now() ,
                cpu : Math.round( stats_hw_cpu_last * 10 ) / 10, 
                ram : Math.round( stats_hw_ram_last * 1000 ) / 10,
                connections : stats_request_ip_list.length,
                requestsCount : stats_request_count
            };
        } , 1000 );
    };
    stats_reset = function() {
        stats_request_ip_list = [];
        stats_request_count = 0;
    };
    // 
    stats_RecordRequest = function( req ) {
        stats_request_count ++ ;
        if( stats_request_ip_list.indexOf( req.ip ) == -1 ) stats_request_ip_list.push( req.ip );
    }
    /** 
     * @description Measure the CPU usage calculated between two different CPU usage samples
     * @param {function} cb A callback function the result is passed to
     * @param {number} [core=-1] The CPU core index to measure. When is not greater than -1 then it is "averaged" for all CPU cores.
     * @param {number} [sampleMs=1000]  The number of milliseconds between the CPU usage samples
     */    
    stats_cpuUsage = function(cb, core, sampleMs) {
        // https://stackoverflow.com/a/65952194/2496170
        var deltaUsed;
        var deltaIdle;
        var timesKeys = ["user", "nice", "sys", "irq"];
        var allCores = null === core || !(core > -1);
        var byCore = (cpu, i) => allCores || core === i;
        var bySampleKey = (sample, key) => sample.filter(byCore).reduce((sum, cpu) => sum + cpu.times[key], 0);
        var sample0 = os.cpus();
        setTimeout(function() {
            var sample1 = os.cpus();
            deltaUsed = timesKeys.reduce(
                (diff, key) => diff + bySampleKey(sample1, key) - bySampleKey(sample0, key), 0);
            deltaIdle = bySampleKey(sample1, "idle") - bySampleKey(sample0, "idle");
            if ("function" === typeof cb) cb(100 * (deltaUsed / (deltaUsed + deltaIdle)));
        }, sampleMs || 1000);
    }
    //
})();