Metricsgen generates interface implementation that measures execution time of all methods using prometheus SDK.
go get -u github.com/gojuno/metricsgen
Imagine you have the following interface:
type Example interface {
Do(a, b string) error
Another(c string)
}Here is how to generate metrics decorator for this interface:
metricsgen -i github.com/gojuno/metricsgen/tests.Example -o ./tests/
The result will be:
package tests
/*
DO NOT EDIT!
This code was generated automatically using github.com/gojuno/metricsgen v1.2
The original interface "Example" can be found in github.com/gojuno/metricsgen/tests
*/
import (
"time"
"github.com/prometheus/client_golang/prometheus"
)
type ExampleMetrics struct {
next Example
summary *prometheus.SummaryVec
instanceName string
}
func NewExampleMetricsSummary(metricName string) *prometheus.SummaryVec {
sv := prometheus.NewSummaryVec(
prometheus.SummaryOpts{
Name: metricName,
Help: metricName,
},
[]string{"instance_name", "method"},
)
prometheus.MustRegister(sv)
return sv
}
func NewExampleMetricsWithSummary(next Example, instanceName string, sv *prometheus.SummaryVec) *ExampleMetrics {
return &ExampleMetrics{
next: next,
summary: sv,
instanceName: instanceName,
}
}
func (m *ExampleMetrics) Another(p string) {
defer m.observe("Another", time.Now())
m.next.Another(p)
}
func (m *ExampleMetrics) Do(p string, p1 string) (r error) {
defer m.observe("Do", time.Now())
return m.next.Do(p, p1)
}
func (m *ExampleMetrics) observe(method string, startedAt time.Time) {
duration := time.Since(startedAt)
m.summary.WithLabelValues(m.instanceName, method).Observe(duration.Seconds())
}Decorator creates prometheus summary vector with two labels:
instanceName. it's used to separate different instances of single interface to avoid metric name collisions.method. Interface method name.
//create and register summary vector
sv := NewExampleMetricsSummary("example_metric_name")
//create two implementations of the Example interface decorated with methods' execution time metrics
ex1 := NewExampleMetricsWithSummary(next, sv, "instance_1")
ex2 := NewExampleMetricsWithSummary(next, sv, "instance_2")