Function TestHashForCollisionRate

pkg/util/hash_test.go:34–62

Verify HashForTraceID doesn't collide within reasonable numbers, and estimate the hash collision rate if it does.

(t *testing.T)

// Verify HashForTraceID doesn't collide within reasonable numbers, and estimate the hash collision rate if it does.
func TestHashForCollisionRate(t *testing.T) {
	var (
		n      = 1_000_000
		tokens = map[uint64]struct{}{}
		IDs    = make([][]byte, 0, n)
	)

	for i := 0; i < n; i++ {
		traceID := make([]byte, 16)
		_, err := rand.Read(traceID)
		require.NoError(t, err)

		IDs = append(IDs, traceID)
		tokens[HashForTraceID(traceID)] = struct{}{}
	}

	// Ensure no duplicate span IDs accidentally generated
	sort.Slice(IDs, func(i, j int) bool {
		return bytes.Compare(IDs[i], IDs[j]) == -1
	})
	for i := 1; i < len(IDs); i++ {
		if bytes.Equal(IDs[i-1], IDs[i]) {
			panic("same trace ID was generated, oops")
		}
	}

	missing := n - len(tokens)
	require.Zerof(t, missing, "missing 1 out of every %.2f trace ids", float32(n)/float32(missing))
}