service metrics middleware

service_metrics_middleware.go

package main

import (
	"context"
	
	"github.com/graymeta/mf2/services/data_api/metrics"
)

func main() {
	var svc SVC
	svc := NewFooService()
	svc = NewMetricsMiddleware(svc)
	
	// do something with svc
}

type Foo string

type SVC interface {
	Read(ctx context.Context, id string)(Foo, error)
	Delete(ctx context.Context, id string) error
}

type FooService struct {}

func NewFooService() SVC {
	return &FooService{}
}

func (s *FooService) Read(ctx context.Context, id string)(Foo, error){
	// read the Foo from somewhere
	return Foo(id), nil
}

func (s *FooService) Delete(ctx context.Context, id string) error {
	// do some delete logic
	return nil
}

type MetricMiddleware struct {
	metrics metrics.Client
	svc SVC
}

func NewMetricsMiddleware(fs SVC) SVC {
	return &MetricMiddleware{
		metrics: metrics.NewClient("foo"),
		svc: fs,
	}
}

func (s *MetricMiddleware) Read(ctx context.Context, id string) (f Foo, e error) {
	defer s.metrics.NewTimer("read")()
	s.metrics.IncReqs("read")
	
	defer func() {
		if e != nil {
			s.metrics.IncErrs("read")
		}
	}()
	
	return s.svc.Read(ctx, id)
}

func (s *MetricMiddleware) Delete(ctx context.Context, id string) (e error) {
	defer s.metrics.NewTimer("read")()
	s.metrics.IncReqs("read")
	
	defer func() {
		if e != nil {
			s.metrics.IncErrs("read")
		}
	}()
	
	return s.svc.Delete(ctx, id)
}