Function TestAlreadyRegisteredCollision

prometheus/registry_test.go:1127–1184

TestAlreadyRegistered will fail with the old, weaker hash function. It is taken from https://play.golang.org/p/HpV7YE6LI_4 , authored by @awilliams.

(t *testing.T)

// TestAlreadyRegistered will fail with the old, weaker hash function.  It is
// taken from https://play.golang.org/p/HpV7YE6LI_4 , authored by @awilliams.
func TestAlreadyRegisteredCollision(t *testing.T) {
	reg := prometheus.NewRegistry()

	for i := 0; i < 10000; i++ {
		// A collector should be considered unique if its name and const
		// label values are unique.

		name := fmt.Sprintf("test-collector-%010d", i)

		collector := collidingCollector{
			i:    i,
			name: name,

			a: prometheus.NewCounter(prometheus.CounterOpts{
				Name: "my_collector_a",
				ConstLabels: prometheus.Labels{
					"name": name,
					"type": "test",
				},
			}),
			b: prometheus.NewCounter(prometheus.CounterOpts{
				Name: "my_collector_b",
				ConstLabels: prometheus.Labels{
					"name": name,
					"type": "test",
				},
			}),
			c: prometheus.NewCounter(prometheus.CounterOpts{
				Name: "my_collector_c",
				ConstLabels: prometheus.Labels{
					"name": name,
					"type": "test",
				},
			}),
			d: prometheus.NewCounter(prometheus.CounterOpts{
				Name: "my_collector_d",
				ConstLabels: prometheus.Labels{
					"name": name,
					"type": "test",
				},
			}),
		}

		// Register should not fail, since each collector has a unique
		// set of sub-collectors, determined by their names and const label values.
		if err := reg.Register(&collector); err != nil {
			are := &prometheus.AlreadyRegisteredError{}
			if !errors.As(err, are) {
				t.Fatal(err)
			}

			previous := are.ExistingCollector.(*collidingCollector)
			current := are.NewCollector.(*collidingCollector)

			t.Errorf("Unexpected registration error: %q\nprevious collector: %s (i=%d)\ncurrent collector %s (i=%d)", are, previous.name, previous.i, current.name, current.i)
		}
	}
}