Function ExampleWrapCollectorWith

prometheus/examples_test.go:793–856

Using WrapCollectorWith to un-register metrics registered by a third party lib. newThirdPartyLibFoo illustrates a constructor from a third-party lib that does not expose any way to un-register metrics.

()

// newThirdPartyLibFoo illustrates a constructor from a third-party lib that does
// not expose any way to un-register metrics.
func ExampleWrapCollectorWith() {
	reg := prometheus.NewRegistry()

	// We want to create two instances of thirdPartyLibFoo, each one wrapped with
	// its "instance" label.
	firstReg := prometheus.NewRegistry()
	_ = newThirdPartyLibFoo(firstReg)
	firstCollector := prometheus.WrapCollectorWith(prometheus.Labels{"instance": "first"}, firstReg)
	reg.MustRegister(firstCollector)

	secondReg := prometheus.NewRegistry()
	_ = newThirdPartyLibFoo(secondReg)
	secondCollector := prometheus.WrapCollectorWith(prometheus.Labels{"instance": "second"}, secondReg)
	reg.MustRegister(secondCollector)

	// So far we have illustrated that we can create two instances of thirdPartyLibFoo,
	// wrapping each one's metrics with some const label.
	// This is something we could've achieved by doing:
	// newThirdPartyLibFoo(prometheus.WrapRegistererWith(prometheus.Labels{"instance": "first"}, reg))
	metricFamilies, err := reg.Gather()
	if err != nil {
		panic("unexpected behavior of registry")
	}
	fmt.Println("Both instances:")
	fmt.Println(toNormalizedJSON(sanitizeMetricFamily(metricFamilies[0])))

	// Now we want to unregister first Foo's metrics, and then register them again.
	// This is not possible by passing a wrapped Registerer to newThirdPartyLibFoo,
	// because we have already lost track of the registered Collectors,
	// however since we've collected Foo's metrics in it's own Registry, and we have registered that
	// as a specific Collector, we can now de-register them:
	unregistered := reg.Unregister(firstCollector)
	if !unregistered {
		panic("unexpected behavior of registry")
	}

	metricFamilies, err = reg.Gather()
	if err != nil {
		panic("unexpected behavior of registry")
	}
	fmt.Println("First unregistered:")
	fmt.Println(toNormalizedJSON(sanitizeMetricFamily(metricFamilies[0])))

	// Now we can create another instance of Foo with {instance: "first"} label again.
	firstRegAgain := prometheus.NewRegistry()
	_ = newThirdPartyLibFoo(firstRegAgain)
	firstCollectorAgain := prometheus.WrapCollectorWith(prometheus.Labels{"instance": "first"}, firstRegAgain)
	reg.MustRegister(firstCollectorAgain)

	metricFamilies, err = reg.Gather()
	if err != nil {
		panic("unexpected behavior of registry")
	}
	fmt.Println("Both again:")
	fmt.Println(toNormalizedJSON(sanitizeMetricFamily(metricFamilies[0])))

	// Output:
	// Both instances: