Merge pull request #30232 from overleaf/ar/convert-clsi-to-es-modules

[clsi] convert to ES modules

GitOrigin-RevId: fb7fa52cc8f678ee31be352e62a5dff95e88008b

services/clsi/test/unit/js/StatsManager.test.js

@@ -0,0 +1,170 @@
+import { expect, describe, it, vi } from 'vitest'
+import StatsManager from '../../../app/js/StatsManager.js'
+
+const { sampleByHash, sampleRequest } = StatsManager
+
+// Mocks allow us to import Metrics.js twice without getting errors.
+vi.mock('@overleaf/metrics', () => ({
+  prom: {
+    Gauge: vi.fn(),
+    Counter: vi.fn(),
+    Histogram: vi.fn(),
+  },
+}))
+
+describe('StatsManager', function () {
+  describe('sampleByHash', function () {
+    it('should always return false for a sample percentage of 0', function () {
+      for (let i = 0; i < 100; i++) {
+        const key = `test-key-${i}`
+        expect(sampleByHash(key, 0), `key ${key} should be false`).to.be.false
+      }
+    })
+
+    it('should always return false for a negative sample percentage', function () {
+      for (let i = 0; i < 100; i++) {
+        const key = `test-key-${i}`
+        expect(sampleByHash(key, -10), `key ${key} should be false`).to.be.false
+      }
+    })
+
+    it('should always return true for a sample percentage of 100', function () {
+      // This isn't strictly true, if the hash is exactly 0xffffffff, then the percentile is 100
+      // and 100 < 100 is false. But the chances of that are 1 in 4 billion.
+      for (let i = 0; i < 100; i++) {
+        const key = `test-key-${i}`
+        expect(sampleByHash(key, 100), `key ${key} should be true`).to.be.true
+      }
+    })
+
+    it('should return the expected number of results for a sample percentage of 75', function () {
+      // This isn't strictly true, if the hash is exactly 0xffffffff, then the percentile is 100
+      // and 100 < 100 is false. But the chances of that are 1 in 4 billion.
+      let count = 0
+      for (let i = 0; i < 100; i++) {
+        const key = `test-key-${i}`
+        count += sampleByHash(key, 75) ? 1 : 0
+      }
+      // Actual result is 74, it's deterministic but the test allows the algorithm to change
+      expect(count).to.be.within(70, 80)
+    })
+
+    it('should return true when the hash is within the sample percentage', function () {
+      // The MD5 hash of 'test-key-in' gives a percentile of 13
+      const key = 'test-key-in'
+      const percentage = 40
+      expect(sampleByHash(key, percentage)).to.be.true
+    })
+
+    it('should return false when the hash is outside the sample percentage', function () {
+      // The MD5 hash of 'test-key-outer' gives a percentile of 47
+      const key = 'test-key-outer'
+      const percentage = 40
+      expect(sampleByHash(key, percentage)).to.be.false
+    })
+
+    it('should produce consistent results for the same key', function () {
+      const key = 'consistent-key'
+      const percentage = 50
+      const result1 = sampleByHash(key, percentage)
+      const result2 = sampleByHash(key, percentage)
+      expect(result1).to.equal(result2)
+    })
+
+    it('should handle different keys correctly', function () {
+      // MD5('key1') => percentile 76
+      // MD5('key2') => percentile 47
+      expect(sampleByHash('key1', 80)).to.be.true
+      expect(sampleByHash('key1', 70)).to.be.false
+      expect(sampleByHash('key2', 50)).to.be.true
+      expect(sampleByHash('key2', 40)).to.be.false
+    })
+
+    it('should be monotonic with respect to percentage', function () {
+      const key = 'test-key'
+      const percentile = 32
+      for (let i = 0; i <= 100; i++) {
+        const result = sampleByHash(key, i)
+        if (i <= percentile) {
+          expect(result, `percentage ${i} should be false`).to.be.false
+        } else {
+          expect(result, `percentage ${i} should be true`).to.be.true
+        }
+      }
+    })
+  })
+
+  describe('sampleRequest', function () {
+    it('should return undefined if there is no user_id', function () {
+      const request = { metricsOpts: {} }
+      const percentage = 50
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined if the path is health-check', function () {
+      const request = {
+        user_id: 'some-user',
+        metricsOpts: { path: 'health-check' },
+      }
+      const percentage = 100
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined if the path is clsi-perf', function () {
+      const request = {
+        user_id: 'some-user',
+        metricsOpts: { path: 'clsi-perf' },
+      }
+      const percentage = 100
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined for a health-check even if the user would be sampled', function () {
+      const request = {
+        user_id: 'test-key-in', // percentile 13
+        metricsOpts: { path: 'health-check' },
+      }
+      const percentage = 40
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined for clsi-perf even if the user would be sampled', function () {
+      const request = {
+        user_id: 'test-key-in', // percentile 13
+        metricsOpts: { path: 'clsi-perf' },
+      }
+      const percentage = 40
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined if the sampling percentage is 0', function () {
+      const request = { user_id: 'some-user', metricsOpts: {} }
+      const percentage = 0
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should return undefined if the sampling percentage is negative', function () {
+      const request = { user_id: 'some-user', metricsOpts: {} }
+      const percentage = -10
+      expect(sampleRequest(request, percentage)).to.be.undefined
+    })
+
+    it('should sample if metricsOpts has no path', function () {
+      const request = { user_id: 'test-key-in', metricsOpts: {} } // percentile 13
+      const percentage = 40
+      expect(sampleRequest(request, percentage)).to.be.true
+    })
+
+    it('should return true for a request that should be sampled', function () {
+      const request = { user_id: 'test-key-in', metricsOpts: {} } // percentile 13
+      const percentage = 40
+      expect(sampleRequest(request, percentage)).to.be.true
+    })
+
+    it('should return false for a request that should not be sampled', function () {
+      const request = { user_id: 'test-key-outer', metricsOpts: {} } // percentile 47
+      const percentage = 40
+      expect(sampleRequest(request, percentage)).to.be.false
+    })
+  })
+})