Express Telemetry

• Express Middleware
• Triggers
  • on high server load (long delays in the eventLoop)
  • on high response times (high response times)
  • on high machine load (high cpu or memory usage)

Inspired from Electrode's auto-ssr for Hapi.

Installation

npm install --save express-telemetry-middleware

Usage

The installTelemetry instructs the app to use the 3 triggers as middlewares.

if any of the triggers hits a threshold, appOnHighLoad will be set to true.

import installTelemetry from 'express-telemetry-middleware'
import express from 'express';

const app = express();
installTelemetry(app, options);

route("/home", function(req, res) {
  console.log(req.appOnHighLoad);
})

Options

Machine load:

• loadThreshold || 4;
• memoryThreshold || 80%;

Server Load:

• delayThresholdMS || 20

Response Time:

• longResponseThreshold || 5000;

• longResponseAmount || 6;

• disableExpiryMins || 2;

• headerDigits (3)

• headerName (X-Response-Time)

• suffix (false)

added req attributes

Machine load:

• req.highMachineLoad

Server Load:

• req.eventLoopDelay
• req.highServerLoad

Response Time:

• req.highResponseTimeExpiration
• req.highResponseTime
• req.numberOfLongResponses