Fix startup crash

Version 3.2.0 crashes on startup because it calls buildPromKey() without
arguments. To avoid this kind of obvious bug to happen again, I added
some basic acceptance tests.

libraries/metrics/.circleci/config.yml

@@ -0,0 +1,11 @@
+version: 2.1
+
+orbs:
+  node: circleci/node@3.0.0
+
+workflows:
+  test:
+    jobs:
+      - node/test:
+          version: "10.22"
+          override-ci-command: npm install

libraries/metrics/index.js

@@ -28,7 +28,7 @@ function configure(opts = {}) {
  */
 function initialize(_name, opts = {}) {
   configure({ ...opts, appName: _name })
-  collectDefaultMetrics({ timeout: 5000, prefix: buildPromKey() })
+  collectDefaultMetrics({ timeout: 5000, prefix: '' })
 
   console.log(`ENABLE_TRACE_AGENT set to ${process.env.ENABLE_TRACE_AGENT}`)
   if (process.env.ENABLE_TRACE_AGENT === 'true') {

libraries/metrics/package.json

@@ -35,7 +35,9 @@
   },
   "scripts": {
     "lint": "eslint --max-warnings 0 .",
-    "test": "mocha --reporter spec --recursive --exit --grep=$MOCHA_GREP test/unit",
+    "test:unit": "mocha --reporter spec --recursive --exit --grep=$MOCHA_GREP test/unit",
+    "test:acceptance": "mocha --reporter spec --recursive --exit --grep=$MOCHA_GREP test/acceptance",
+    "test": "npm run test:unit && npm run test:acceptance",
     "format": "prettier-eslint $PWD'/**/*.js' --list-different",
     "format:fix": "prettier-eslint $PWD'/**/*.js' --write"
   }

libraries/metrics/test/acceptance/metrics_tests.js

@@ -0,0 +1,115 @@
+const os = require('os')
+const { expect } = require('chai')
+const Metrics = require('../..')
+
+const HOSTNAME = os.hostname()
+const APP_NAME = 'test-app'
+
+describe('Metrics module', function() {
+  before(function() {
+    Metrics.initialize(APP_NAME)
+  })
+
+  describe('at startup', function() {
+    it('increments the process_startup counter', async function() {
+      await expectMetricValue('process_startup', 1)
+    })
+
+    it('collects default metrics', async function() {
+      const metric = await getMetric('process_cpu_user_seconds_total')
+      expect(metric).to.exist
+    })
+  })
+
+  describe('inc()', function() {
+    it('increments counts by 1', async function() {
+      Metrics.inc('duck_count')
+      await expectMetricValue('duck_count', 1)
+      Metrics.inc('duck_count')
+      Metrics.inc('duck_count')
+      await expectMetricValue('duck_count', 3)
+    })
+
+    it('escapes special characters in the key', async function() {
+      Metrics.inc('show.me the $!!')
+      await expectMetricValue('show_me_the____', 1)
+    })
+  })
+
+  describe('count()', function() {
+    it('increments counts by the given count', async function() {
+      Metrics.count('rabbit_count', 5)
+      await expectMetricValue('rabbit_count', 5)
+      Metrics.count('rabbit_count', 6)
+      Metrics.count('rabbit_count', 7)
+      await expectMetricValue('rabbit_count', 18)
+    })
+  })
+
+  describe('summary()', function() {
+    it('collects observations', async function() {
+      Metrics.summary('oven_temp', 200)
+      Metrics.summary('oven_temp', 300)
+      Metrics.summary('oven_temp', 450)
+      const sum = await getSummarySum('oven_temp')
+      expect(sum).to.equal(950)
+    })
+  })
+
+  describe('timing()', function() {
+    it('collects timings', async function() {
+      Metrics.timing('sprint_100m', 10)
+      Metrics.timing('sprint_100m', 20)
+      Metrics.timing('sprint_100m', 30)
+      const sum = await getSummarySum('timer_sprint_100m')
+      expect(sum).to.equal(60)
+    })
+  })
+
+  describe('gauge()', function() {
+    it('records values', async function() {
+      Metrics.gauge('water_level', 1.5)
+      await expectMetricValue('water_level', 1.5)
+      Metrics.gauge('water_level', 4.2)
+      await expectMetricValue('water_level', 4.2)
+    })
+  })
+
+  describe('globalGauge()', function() {
+    it('records values without a host label', async function() {
+      Metrics.globalGauge('tire_pressure', 99.99)
+      const { value, labels } = await getMetricValue('tire_pressure')
+      expect(value).to.equal(99.99)
+      expect(labels.host).to.equal('')
+      expect(labels.app).to.equal(APP_NAME)
+    })
+  })
+})
+
+function getMetric(key) {
+  return Metrics.register.getSingleMetric(key)
+}
+
+async function getSummarySum(key) {
+  const metric = getMetric(key)
+  const item = await metric.get()
+  for (const value of item.values) {
+    if (value.metricName === `${key}_sum`) {
+      return value.value
+    }
+  }
+  return null
+}
+
+async function getMetricValue(key) {
+  const metric = getMetric(key)
+  const item = await metric.get()
+  return item.values[0]
+}
+
+async function expectMetricValue(key, expectedValue) {
+  const value = await getMetricValue(key)
+  expect(value.value).to.equal(expectedValue)
+  expect(value.labels.host).to.equal(HOSTNAME)
+  expect(value.labels.app).to.equal(APP_NAME)
+}