Copyright 2017 The Prometheus Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

package prometheus
Observer is the interface that wraps the Observe method, which is used by Histogram and Summary to add observations.
type Observer interface {
	Observe(float64)
}
The ObserverFunc type is an adapter to allow the use of ordinary functions as Observers. If f is a function with the appropriate signature, ObserverFunc(f) is an Observer that calls f. This adapter is usually used in connection with the Timer type, and there are two general use cases: The most common one is to use a Gauge as the Observer for a Timer. See the "Gauge" Timer example. The more advanced use case is to create a function that dynamically decides which Observer to use for observing the duration. See the "Complex" Timer example.
type ObserverFunc func(float64)
Observe calls f(value). It implements Observer.
func ( ObserverFunc) ( float64) {
	()
}
ObserverVec is an interface implemented by `HistogramVec` and `SummaryVec`.
type ObserverVec interface {
	GetMetricWith(Labels) (Observer, error)
	GetMetricWithLabelValues(lvs ...string) (Observer, error)
	With(Labels) Observer
	WithLabelValues(...string) Observer
	CurryWith(Labels) (ObserverVec, error)
	MustCurryWith(Labels) ObserverVec

	Collector