feat(metrics): add runtime metrics

docs/metrics.asciidoc

@@ -60,3 +60,71 @@ This value is normalized by the number of CPU cores and it ranges from 0 to 100%
 
 The Resident Set Size,
 the amount of memory the process occupies in main memory (RAM).
+
+[float]
+[[metric-nodejs.handles.active]]
+=== `nodejs.handles.active`
+
+* *Type:* Long
+* *Format:* Counter
+
+The number of active libuv handles,
+likely held open by currently running I/O operations.
+
+[float]
+[[metric-nodejs.requests.active]]
+=== `nodejs.requests.active`
+
+* *Type:* Long
+* *Format:* Counter
+
+The number of active libuv requests,
+likely waiting for a response to an I/O operation.
+
+[float]
+[[metric-system.process.cpu.user.norm.pct]]
+=== `system.process.cpu.user.norm.pct`
+
+* *Type:* Long
+* *Format:* Counter
+
+The number of CPU cycles spent executing application code.
+
+[float]
+[[metric-system.process.cpu.system.norm.pct]]
+=== `system.process.cpu.system.norm.pct`
+
+* *Type:* Long
+* *Format:* Counter
+
+The number of CPU cycles spent executing kernel code as a result of application activity.
+
+[float]
+[[metric-nodejs.eventloop.delay.avg.ms]]
+=== `nodejs.eventloop.delay.avg.ms`
+
+* *Type:* Float
+* *Format:* Milliseconds
+
+The number of milliseconds of event loop delay.
+Event loop delay is sampled every 10 milliseconds.
+Delays shorter than 10ms may not be observed,
+for example if a blocking operation starts and ends within the same sampling period.
+
+[float]
+[[metric-nodejs.memory.heap.allocated.bytes]]
+=== `nodejs.memory.heap.allocated.bytes`
+
+* *Type:* Long
+* *Format:* Bytes
+
+The current allocated heap size in bytes.
+
+[float]
+[[metric-nodejs.memory.heap.used.bytes]]
+=== `nodejs.memory.heap.used.bytes`
+
+* *Type:* Long
+* *Format:* Bytes
+
+The currently used heap size in bytes.

lib/metrics/platforms/generic/index.js

@@ -4,6 +4,8 @@ const os = require('os')
 
 const semver = require('semver')
 
+const Stats = require('./stats')
+
 module.exports = function createSystemMetrics (registry) {
   // Base system metrics
   registry.getOrCreateGauge(
@@ -22,10 +24,18 @@ module.exports = function createSystemMetrics (registry) {
   // Process metrics
   // NOTE: Process CPU metrics are not supported on 6.0.x
   if (semver.satisfies(process.versions.node, '>=6.1')) {
-    registry.getOrCreateGauge(
+    const stats = new Stats()
+    registry.registerCollector(stats)
+
+    const metrics = [
       'system.process.cpu.total.norm.pct',
-      require('./process-cpu')
-    )
+      'system.process.cpu.system.norm.pct',
+      'system.process.cpu.user.norm.pct'
+    ]
+
+    for (let metric of metrics) {
+      registry.getOrCreateGauge(metric, () => stats.toJSON()[metric])
+    }
   }
   registry.getOrCreateGauge(
     'system.process.memory.rss.bytes',

lib/metrics/platforms/generic/process-cpu.js

@@ -7,5 +7,10 @@ const processTop = require('./process-top')()
 const cpus = os.cpus()
 
 module.exports = function processCPUUsage () {
-  return processTop.cpu().percent / cpus.length
+  const cpu = processTop.cpu()
+  return {
+    total: cpu.percent / cpus.length,
+    user: (cpu.user / cpu.time) / cpus.length,
+    system: (cpu.system / cpu.time) / cpus.length
+  }
 }

lib/metrics/platforms/generic/stats.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const processCpu = require('./process-cpu')
+
+class Stats {
+  constructor () {
+    this.stats = {
+      'system.process.cpu.total.norm.pct': 0,
+      'system.process.cpu.system.norm.pct': 0,
+      'system.process.cpu.user.norm.pct': 0
+    }
+  }
+
+  toJSON () {
+    return this.stats
+  }
+
+  collect (cb) {
+    const cpu = processCpu()
+    this.stats['system.process.cpu.total.norm.pct'] = cpu.total
+    this.stats['system.process.cpu.system.norm.pct'] = cpu.system
+    this.stats['system.process.cpu.user.norm.pct'] = cpu.user
+
+    if (cb) process.nextTick(cb)
+  }
+}
+
+module.exports = Stats

lib/metrics/platforms/generic/system-cpu.js

@@ -32,7 +32,7 @@ function cpuAverage () {
 function cpuPercent (last, next) {
   const idle = next.idle - last.idle
   const total = next.total - last.total
-  return 1 - idle / total
+  return 1 - idle / total || 0
 }
 
 let last = cpuAverage()

lib/metrics/platforms/linux/index.js

@@ -2,22 +2,12 @@
 
 const Stats = require('./stats')
 
-module.exports = function createSystemMetrics (registry, reportingIntervalInSeconds) {
+module.exports = function createSystemMetrics (registry) {
   const stats = new Stats()
-  stats.start(reportingIntervalInSeconds)
 
-  const metrics = [
-    'system.cpu.total.norm.pct',
-    'system.memory.total',
-    'system.memory.actual.free',
-    'system.process.cpu.total.norm.pct',
-    'system.process.memory.size',
-    'system.process.memory.rss.bytes'
-  ]
+  registry.registerCollector(stats)
 
-  for (let metric of metrics) {
+  for (let metric of Object.keys(stats.toJSON())) {
     registry.getOrCreateGauge(metric, () => stats.toJSON()[metric])
   }
-
-  registry.collector = stats
 }