Manfred Touron 5448f25fd6
glide up
2017-05-18 23:33:43 +02:00

136 lines
4.4 KiB
Go

package addsvc
// This file contains methods to make individual endpoints from services,
// request and response types to serve those endpoints, as well as encoders and
// decoders for those types, for all of our supported transport serialization
// formats. It also includes endpoint middlewares.
import (
"fmt"
"time"
"golang.org/x/net/context"
"github.com/go-kit/kit/endpoint"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/metrics"
)
// Endpoints collects all of the endpoints that compose an add service. It's
// meant to be used as a helper struct, to collect all of the endpoints into a
// single parameter.
//
// In a server, it's useful for functions that need to operate on a per-endpoint
// basis. For example, you might pass an Endpoints to a function that produces
// an http.Handler, with each method (endpoint) wired up to a specific path. (It
// is probably a mistake in design to invoke the Service methods on the
// Endpoints struct in a server.)
//
// In a client, it's useful to collect individually constructed endpoints into a
// single type that implements the Service interface. For example, you might
// construct individual endpoints using transport/http.NewClient, combine them
// into an Endpoints, and return it to the caller as a Service.
type Endpoints struct {
SumEndpoint endpoint.Endpoint
ConcatEndpoint endpoint.Endpoint
}
// Sum implements Service. Primarily useful in a client.
func (e Endpoints) Sum(ctx context.Context, a, b int) (int, error) {
request := sumRequest{A: a, B: b}
response, err := e.SumEndpoint(ctx, request)
if err != nil {
return 0, err
}
return response.(sumResponse).V, response.(sumResponse).Err
}
// Concat implements Service. Primarily useful in a client.
func (e Endpoints) Concat(ctx context.Context, a, b string) (string, error) {
request := concatRequest{A: a, B: b}
response, err := e.ConcatEndpoint(ctx, request)
if err != nil {
return "", err
}
return response.(concatResponse).V, response.(concatResponse).Err
}
// MakeSumEndpoint returns an endpoint that invokes Sum on the service.
// Primarily useful in a server.
func MakeSumEndpoint(s Service) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
sumReq := request.(sumRequest)
v, err := s.Sum(ctx, sumReq.A, sumReq.B)
if err == ErrIntOverflow {
return nil, err // special case; see comment on ErrIntOverflow
}
return sumResponse{
V: v,
Err: err,
}, nil
}
}
// MakeConcatEndpoint returns an endpoint that invokes Concat on the service.
// Primarily useful in a server.
func MakeConcatEndpoint(s Service) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
concatReq := request.(concatRequest)
v, err := s.Concat(ctx, concatReq.A, concatReq.B)
return concatResponse{
V: v,
Err: err,
}, nil
}
}
// EndpointInstrumentingMiddleware returns an endpoint middleware that records
// the duration of each invocation to the passed histogram. The middleware adds
// a single field: "success", which is "true" if no error is returned, and
// "false" otherwise.
func EndpointInstrumentingMiddleware(duration metrics.Histogram) endpoint.Middleware {
return func(next endpoint.Endpoint) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
defer func(begin time.Time) {
duration.With("success", fmt.Sprint(err == nil)).Observe(time.Since(begin).Seconds())
}(time.Now())
return next(ctx, request)
}
}
}
// EndpointLoggingMiddleware returns an endpoint middleware that logs the
// duration of each invocation, and the resulting error, if any.
func EndpointLoggingMiddleware(logger log.Logger) endpoint.Middleware {
return func(next endpoint.Endpoint) endpoint.Endpoint {
return func(ctx context.Context, request interface{}) (response interface{}, err error) {
defer func(begin time.Time) {
logger.Log("error", err, "took", time.Since(begin))
}(time.Now())
return next(ctx, request)
}
}
}
// These types are unexported because they only exist to serve the endpoint
// domain, which is totally encapsulated in this package. They are otherwise
// opaque to all callers.
type sumRequest struct{ A, B int }
type sumResponse struct {
V int
Err error
}
type concatRequest struct{ A, B string }
type concatResponse struct {
V string
Err error
}