Extra metrics (#34)

* Make sure to reset mock timers

* Add some helpful metrics

README.md

@@ -20,6 +20,9 @@ automatically for you when you do `require('prom-client')`.
 
 NOTE: Some of the metrics, concerning File Descriptors and Memory, are only available on Linux.
 
+In addition, some Node-specific metrics are included, such as event loop lag, and active handles. See what metrics there are in
+[lib/metrics](lib/metrics).
+
 The function returned from `defaultMetrics` takes 2 options, a blacklist of metrics to skip, and a timeout for how often the probe should
 be fired. By default all probes are launched every 10 seconds, but this can be modified like this:
 

lib/defaultMetrics.js

@@ -5,13 +5,19 @@ var processStartTime = require('./metrics/processStartTime');
 var osMemoryHeap = require('./metrics/osMemoryHeap');
 var processOpenFileDescriptors = require('./metrics/processOpenFileDescriptors');
 var processMaxFileDescriptors = require('./metrics/processMaxFileDescriptors');
+var eventLoopLag = require('./metrics/eventLoopLag');
+var processHandles = require('./metrics/processHandles');
+var processRequests = require('./metrics/processRequests');
 
 var metrics = {
     processCpuTotal: processCpuTotal,
     processStartTime: processStartTime,
     osMemoryHeap: osMemoryHeap,
     processOpenFileDescriptors: processOpenFileDescriptors,
-    processMaxFileDescriptors: processMaxFileDescriptors
+    processMaxFileDescriptors: processMaxFileDescriptors,
+    eventLoopLag: eventLoopLag,
+    processHandles: processHandles,
+    processRequests: processRequests
 };
 
 var existingInterval = null;

lib/metrics/eventLoopLag.js

@@ -0,0 +1,20 @@
+'use strict';
+
+var Gauge = require('../gauge');
+
+function reportEventloopLag(start, gauge){
+    var delta = process.hrtime(start);
+    var nanosec = delta[0] * 1e9 + delta[1];
+    var ms = nanosec / 1e6;
+
+    gauge.set(Math.round(ms));
+}
+
+module.exports = function() {
+    var gauge = new Gauge('node_eventloop_lag_milliseconds', 'Lag of event loop in milliseconds.');
+
+    return function() {
+        var start = process.hrtime();
+        setImmediate(reportEventloopLag, start, gauge);
+    };
+};

lib/metrics/processHandles.js

@@ -0,0 +1,17 @@
+'use strict';
+
+var Gauge = require('../gauge');
+
+module.exports = function() {
+    // Don't do anything if the function is removed in later nodes (exists in node@6)
+    if(typeof process._getActiveHandles !== 'function') {
+        return function () {
+        };
+    }
+
+    var gauge = new Gauge('node_active_handles_total', 'Number of active handles.');
+
+    return function() {
+        gauge.set(process._getActiveHandles().length);
+    };
+};

lib/metrics/processRequests.js

@@ -0,0 +1,16 @@
+'use strict';
+
+var Gauge = require('../gauge');
+
+module.exports = function() {    // Don't do anything if the function is removed in later nodes (exists in node@6)
+    if(typeof process._getActiveRequests !== 'function') {
+        return function () {
+        };
+    }
+
+    var gauge = new Gauge('node_active_requests_total', 'Number of active requests.');
+
+    return function() {
+        gauge.set(process._getActiveRequests().length);
+    };
+};

package.json

@@ -13,7 +13,7 @@
   "scripts": {
     "test": "npm run lint && npm run test-unit",
     "lint": "eslint --ignore-pattern doc/ --ignore-path .gitignore .",
-    "test-unit": "mocha test/"
+    "test-unit": "mocha --recursive test/"
   },
   "repository": {
     "type": "git",

test/defaultMetrics.js

@@ -53,12 +53,12 @@ describe('defaultMetrics', function() {
 	it('should add metrics to the registry', function() {
 		expect(register.getMetricsAsJSON()).to.have.length(0);
 		interval = defaultMetrics();
-		expect(register.getMetricsAsJSON()).to.have.length(3);
+		expect(register.getMetricsAsJSON()).to.have.length(6);
 	});
 
 	it('should allow blacklisting unwanted metrics', function() {
 		expect(register.getMetricsAsJSON()).to.have.length(0);
 		interval = defaultMetrics(['osMemoryHeap']);
-		expect(register.getMetricsAsJSON()).to.have.length(2);
+		expect(register.getMetricsAsJSON()).to.have.length(5);
 	});
 });

test/gaugeTest.js

@@ -47,6 +47,7 @@ describe('gauge', function() {
 		var clock = sinon.useFakeTimers();
 		instance.setToCurrentTime();
 		expectValue(new Date().getTime());
+		clock.restore();
 	});
 
 	it('should not allow non numbers', function() {

test/metrics/eventLoopLagTest.js

@@ -0,0 +1,31 @@
+'use strict';
+
+describe('eventLoopLag', function () {
+    var expect = require('chai').expect;
+    var register = require('../../index').register;
+    var eventLoopLag = require('../../lib/metrics/eventLoopLag');
+
+    before(function () {
+        register.clear();
+    });
+
+    afterEach(function () {
+        register.clear();
+    });
+
+    it('should add metric to the registry', function (done) {
+        expect(register.getMetricsAsJSON()).to.have.length(0);
+        eventLoopLag()();
+
+        setTimeout(function () {
+            var metrics = register.getMetricsAsJSON();
+            expect(metrics).to.have.length(1);
+
+            expect(metrics[0].help).to.equal('Lag of event loop in milliseconds.');
+            expect(metrics[0].type).to.equal('gauge');
+            expect(metrics[0].name).to.equal('node_eventloop_lag_milliseconds');
+
+            done();
+        }, 5);
+    });
+});

test/metrics/processHandlesTest.js

@@ -0,0 +1,28 @@
+'use strict';
+
+describe('processHandles', function () {
+    var expect = require('chai').expect;
+    var register = require('../../index').register;
+    var processHandles = require('../../lib/metrics/processHandles');
+
+    before(function () {
+        register.clear();
+    });
+
+    afterEach(function () {
+        register.clear();
+    });
+
+    it('should add metric to the registry', function () {
+        expect(register.getMetricsAsJSON()).to.have.length(0);
+
+        processHandles()();
+
+        var metrics = register.getMetricsAsJSON();
+
+        expect(metrics).to.have.length(1);
+        expect(metrics[0].help).to.equal('Number of active handles.');
+        expect(metrics[0].type).to.equal('gauge');
+        expect(metrics[0].name).to.equal('node_active_handles_total');
+    });
+});

test/metrics/processRequestsTest.js

@@ -0,0 +1,28 @@
+'use strict';
+
+describe('processRequests', function () {
+    var expect = require('chai').expect;
+    var register = require('../../index').register;
+    var processRequests = require('../../lib/metrics/processRequests');
+
+    before(function () {
+        register.clear();
+    });
+
+    afterEach(function () {
+        register.clear();
+    });
+
+    it('should add metric to the registry', function () {
+        expect(register.getMetricsAsJSON()).to.have.length(0);
+
+        processRequests()();
+
+        var metrics = register.getMetricsAsJSON();
+
+        expect(metrics).to.have.length(1);
+        expect(metrics[0].help).to.equal('Number of active requests.');
+        expect(metrics[0].type).to.equal('gauge');
+        expect(metrics[0].name).to.equal('node_active_requests_total');
+    });
+});