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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| /** | ||
| * A consistent sampling function that works for arbitrary strings across all JavaScript runtimes. | ||
| */ | ||
| export function isInSample(input: string, sampleRate: number | undefined): boolean { | ||
| if (sampleRate === undefined) { | ||
| return true; | ||
| } else if (sampleRate === 0) { | ||
| return false; | ||
| } | ||
|
|
||
| if (sampleRate < 0 || sampleRate > 1 || isNaN(sampleRate)) { | ||
| console.warn("Sample rate must be between 0 and 1. Ignoring setting."); | ||
|
|
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| return true; | ||
| } | ||
|
|
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| return simpleHash(input) < sampleRate; | ||
| } | ||
|
|
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| /** | ||
| * Simple and consistent string hashing function. | ||
| * Uses character codes and prime numbers for good distribution. | ||
| */ | ||
| function simpleHash(str: string): number { | ||
| let hash = 0; | ||
| const prime = 31; | ||
|
|
||
| for (let i = 0; i < str.length; i++) { | ||
| // Use rolling multiplication instead of Math.pow | ||
| hash = (hash * prime + str.charCodeAt(i)) >>> 0; | ||
| } | ||
|
|
||
| // Use bit operations for better distribution | ||
| hash = ((hash >>> 16) ^ hash) * 0x45d9f3b; | ||
| hash = ((hash >>> 16) ^ hash) * 0x45d9f3b; | ||
| hash = (hash >>> 16) ^ hash; | ||
|
|
||
| return Math.abs(hash) / 0x7fffffff; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,170 @@ | ||
| import { isInSample } from "../src/sampling"; | ||
|
|
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| describe("isInSample", () => { | ||
| describe("edge cases", () => { | ||
| it("should always return true when sample rate is undefined", () => { | ||
| expect(isInSample("test-string", undefined)).toBe(true); | ||
| expect(isInSample("", undefined)).toBe(true); | ||
| expect(isInSample("12345", undefined)).toBe(true); | ||
| }); | ||
|
|
||
| it("should always return false when sample rate is 0", () => { | ||
| expect(isInSample("test-string", 0)).toBe(false); | ||
| expect(isInSample("", 0)).toBe(false); | ||
| expect(isInSample("12345", 0)).toBe(false); | ||
| }); | ||
|
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| it("should always return true when sample rate is 1", () => { | ||
| expect(isInSample("test-string", 1)).toBe(true); | ||
| expect(isInSample("", 1)).toBe(true); | ||
| expect(isInSample("12345", 1)).toBe(true); | ||
| }); | ||
|
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| it("should log warning and return true for invalid sample rates", () => { | ||
| const consoleSpy = jest.spyOn(console, "warn").mockImplementation(); | ||
|
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| expect(isInSample("test", -0.5)).toBe(true); | ||
| expect(consoleSpy).toHaveBeenCalled(); | ||
|
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| consoleSpy.mockClear(); | ||
| expect(isInSample("test", 1.5)).toBe(true); | ||
| expect(consoleSpy).toHaveBeenCalled(); | ||
|
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| consoleSpy.mockRestore(); | ||
| }); | ||
| }); | ||
|
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| describe("consistency", () => { | ||
| it("should return consistent results for the same input", () => { | ||
| const testString = "test-consistency"; | ||
| const sampleRate = 0.5; | ||
| const firstResult = isInSample(testString, sampleRate); | ||
|
|
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| for (let i = 0; i < 100; i++) { | ||
| expect(isInSample(testString, sampleRate)).toBe(firstResult); | ||
| } | ||
| }); | ||
|
|
||
| it("should return different results for different strings", () => { | ||
| const sampleRate = 0.5; | ||
| const results = new Set(); | ||
|
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| ["test1", "test2", "test3", "different", "strings"].forEach((str) => { | ||
| results.add(isInSample(str, sampleRate)); | ||
| }); | ||
|
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| expect(results.size).toBeGreaterThan(1); | ||
| }); | ||
| }); | ||
|
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| describe("distribution", () => { | ||
| it("should roughly match the sample rate for large numbers of inputs", () => { | ||
| const sampleRate = 0.3; | ||
| let inSampleCount = 0; | ||
| const totalTests = 10_000; | ||
|
|
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| // Generate random strings and count how many are in sample | ||
| for (let i = 0; i < totalTests; i++) { | ||
| const testString = `test-${Math.random()}-${i}`; | ||
| if (isInSample(testString, sampleRate)) { | ||
| inSampleCount++; | ||
| } | ||
| } | ||
|
|
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| const actualRate = inSampleCount / totalTests; | ||
| // Allow for 5% deviation from expected rate | ||
| expect(Math.abs(actualRate - sampleRate)).toBeLessThan(0.05); | ||
| }); | ||
| }); | ||
|
|
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| describe("special inputs", () => { | ||
| it("should handle empty strings", () => { | ||
| const sampleRate = 0.5; | ||
| // Just verify it doesn't throw and returns a boolean | ||
| const result = isInSample("", sampleRate); | ||
| expect(typeof result).toBe("boolean"); | ||
| }); | ||
|
|
||
| it("should handle special characters", () => { | ||
| const sampleRate = 0.5; | ||
| const specialChars = "!@#$%^&*()_+-=[]{}|;:,.<>?`~"; | ||
| // Just verify it doesn't throw and returns a boolean | ||
| const result = isInSample(specialChars, sampleRate); | ||
| expect(typeof result).toBe("boolean"); | ||
| }); | ||
|
|
||
| it("should handle very long strings", () => { | ||
| const sampleRate = 0.5; | ||
| const longString = "a".repeat(10000); | ||
| // Just verify it doesn't throw and returns a boolean | ||
| const result = isInSample(longString, sampleRate); | ||
| expect(typeof result).toBe("boolean"); | ||
| }); | ||
|
|
||
| it("should handle unicode characters", () => { | ||
| const sampleRate = 0.5; | ||
| const unicodeString = "你好世界😀🌍👋"; | ||
| // Just verify it doesn't throw and returns a boolean | ||
| const result = isInSample(unicodeString, sampleRate); | ||
| expect(typeof result).toBe("boolean"); | ||
| }); | ||
| }); | ||
|
|
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| // UUID specific tests | ||
| describe("UUID handling", () => { | ||
| it("should maintain consistent sampling across different UUID versions", () => { | ||
| const sampleRate = 0.5; | ||
| const uuidV4 = "123e4567-e89b-12d3-a456-426614174000"; | ||
| const uuidV1 = "123e4567-e89b-11d3-a456-426614174000"; | ||
|
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| // Store initial results | ||
| const v4Result = isInSample(uuidV4, sampleRate); | ||
| const v1Result = isInSample(uuidV1, sampleRate); | ||
|
|
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| // Test consistency 100 times | ||
| for (let i = 0; i < 100; i++) { | ||
| expect(isInSample(uuidV4, sampleRate)).toBe(v4Result); | ||
| expect(isInSample(uuidV1, sampleRate)).toBe(v1Result); | ||
| } | ||
| }); | ||
|
|
||
| it("should handle sequential UUIDs appropriately", () => { | ||
| const sampleRate = 0.5; | ||
| const results = new Set(); | ||
|
|
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| // Generate 1000 sequential UUIDs | ||
| for (let i = 0; i < 1000; i++) { | ||
| const sequentialUUID = `00000000-0000-4000-8000-${i.toString().padStart(12, "0")}`; | ||
| results.add(isInSample(sequentialUUID, sampleRate)); | ||
| } | ||
|
|
||
| // Ensure we got both true and false results | ||
| expect(results.size).toBe(2); | ||
| }); | ||
| }); | ||
|
|
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| describe("performance", () => { | ||
| // Helper to measure execution time | ||
| const measureExecutionTime = (fn: () => void): number => { | ||
| const start = performance.now(); | ||
| fn(); | ||
| return performance.now() - start; | ||
| }; | ||
|
|
||
| it("should handle high-frequency calls efficiently", () => { | ||
| const sampleRate = 0.5; | ||
| const shortString = "test-string"; | ||
| const iterations = 100_000; | ||
|
|
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| const executionTime = measureExecutionTime(() => { | ||
| for (let i = 0; i < iterations; i++) { | ||
| isInSample(shortString, sampleRate); | ||
| } | ||
| }); | ||
|
|
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| // Average time per call should be less than 0.01ms (10 microseconds) | ||
| const avgTimePerCall = executionTime / iterations; | ||
| expect(avgTimePerCall).toBeLessThan(0.01); | ||
| }); | ||
| }); | ||
| }); |