Function cpuUsageThrottle

lib/plugins/cpuUsageThrottle.js:178–206

(req, res, next)

    updateReject();

    function cpuUsageThrottle(req, res, next) {
        // Check to see if this request gets rejected. Since, in updateReject,
        // we calculate a percentage of traffic we are planning to reject, we
        // can use Math.random() (which picks from a uniform distribution in
        // [0,1)) to give us a `plugin._reject`% chance of dropping any given
        // request. This is a stateless was to drop approximatly
        // `plugin._reject`% of traffic.
        var probabilityDraw = Math.random();

        if (probabilityDraw >= plugin._reject) {
            return next(); // Don't reject this request
        }

        var err = new errors.ServiceUnavailableError({
            context: {
                plugin: 'cpuUsageThrottle',
                cpuUsage: plugin._cpu,
                limit: plugin._limit,
                max: plugin._max,
                reject: plugin._reject,
                halfLife: plugin._halfLife,
                interval: plugin._interval,
                probabilityDraw: probabilityDraw,
                lag: plugin._timeoutDelta
            }
        });

        return next(err);
    }

    // Allow the app to clear the timeout for this plugin if necessary, without
    // this we would never be able to clear the event loop when letting Node