Move example LabeledMiddleware out of generated code (#187)

* Move example labeled middleware to _example

* Rename handler to endpoint in endpoints.go

* Export example middlewares

* Rename RequestLatency to Latency

_example/README.md

@@ -0,0 +1,12 @@
+# \_example
+
+`echo.proto` is the service definition for `echo-service`.
+Try generating it with:
+
+```
+truss echo.proto
+```
+
+### middlewares
+
+`middlewares` contains a few example middlewares, including LabeledMiddlewares.

_example/middlewares/labeledmiddlewares.go

@@ -0,0 +1,42 @@
+package middlewares
+
+import (
+	"golang.org/x/net/context"
+	"time"
+
+	"github.com/go-kit/kit/endpoint"
+	"github.com/go-kit/kit/metrics"
+)
+
+// LabeledMiddleware will get passed the endpoint name when passed to
+// WrapAllLabeledExcept, this can be used to write a generic metrics
+// middleware which can send the endpoint name to the metrics collector.
+type LabeledMiddleware func(string, endpoint.Endpoint) endpoint.Endpoint
+
+// ErrorCounter is a LabeledMiddleware, when applied with WrapAllLabeledExcept name will be populated with the endpoint name, and such this middleware will
+// report errors to the metric provider with the endpoint name. Feel free to
+// copy this example middleware to your service.
+func ErrorCounter(errCount metrics.Counter) LabeledMiddleware {
+	return func(name string, in endpoint.Endpoint) endpoint.Endpoint {
+		return func(ctx context.Context, req interface{}) (interface{}, error) {
+			resp, err := in(ctx, req)
+			if err != nil {
+				errCount.With("endpoint", name).Add(1)
+			}
+			return resp, err
+		}
+	}
+}
+
+// Latency is a LabeledMiddleware, reporting the request time of and
+// endpoint along with its name
+func Latency(h metrics.Histogram) LabeledMiddleware {
+	return func(name string, in endpoint.Endpoint) endpoint.Endpoint {
+		return func(ctx context.Context, req interface{}) (interface{}, error) {
+			defer func(begin time.Time) {
+				h.With("endpoint", name).Observe(time.Since(begin).Seconds())
+			}(time.Now())
+			return in(ctx, req)
+		}
+	}
+}

gengokit/middlewares/templates/endpoints.go

@@ -4,11 +4,6 @@ const EndpointsBase = `
 package middlewares
 
 import (
-	"golang.org/x/net/context"
-
-	"github.com/go-kit/kit/endpoint"
-	"github.com/go-kit/kit/metrics"
-
 	"{{.ImportPath -}} /svc"
 )
 
@@ -20,36 +15,21 @@ import (
 // (i.e. applied first)
 func WrapEndpoints(in svc.Endpoints) svc.Endpoints {
 
-	// Pass in the middlewares you want applied to every endpoint.
-	// optionally pass in handlers by name that you want to be excluded
+	// Pass a middleware you want applied to every endpoint.
+	// optionally pass in endpoints by name that you want to be excluded
 	// e.g.
 	// in.WrapAllExcept(authMiddleware, "Status", "Ping")
 
-	// Pass in LabeledMiddlewares you want applied to every endpoint.
-	// These middlewares get passed the handlers name as their first argument when applied.
+	// Pass in a svc.LabeledMiddleware you want applied to every endpoint.
+	// These middlewares get passed the endpoints name as their first argument when applied.
 	// This can be used to write generic metric gathering middlewares that can
-	// report the handler name for free.
-	// in.WrapAllLabeledExcept(errCounter(statsdCounter), "Status", "Ping")
+	// report the endpoint name for free.
+	// github.com/TuneLab/go-truss/_example/middlewares/labeledmiddlewares.go for examples.
+	// in.WrapAllLabeledExcept(errorCounter(statsdCounter), "Status", "Ping")
 
 	// How to apply a middleware to a single endpoint.
 	// in.ExampleEndpoint = authMiddleware(in.ExampleEndpoint)
 
 	return in
 }
-
-// errCounter is a LabeledMiddleware, when applied with WrapAllLabeledExcept
-// name will be populated with the handler name, and such this middleware will
-// report errors to the metric provider with the handler name. Feel free to
-// remove this example middleware
-func errorCounter(errCount metrics.Counter) svc.LabeledMiddleware {
-	return func(name string, in endpoint.Endpoint) endpoint.Endpoint {
-		return func(ctx context.Context, req interface{}) (interface{}, error) {
-			resp, err := in(ctx, req)
-			if err != nil {
-				errCount.With("handler", name).Add(1)
-			}
-			return resp, err
-		}
-	}
-}
 `

gengokit/template/NAME-service/svc/endpoints.gotemplate

@@ -9,7 +9,7 @@ package svc
 // 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.
+// formats.
 
 import (
 	"fmt"
@@ -94,13 +94,13 @@ func (e *Endpoints) WrapAllExcept(middleware endpoint.Middleware, excluded ...st
 	}
 }
 
-// LabeledMiddleware will get passed the handler name when passed to
+// LabeledMiddleware will get passed the endpoint name when passed to
 // WrapAllLabeledExcept, this can be used to write a generic metrics
-// middleware which can send the handler name to the metrics collector.
+// middleware which can send the endpoint name to the metrics collector.
 type LabeledMiddleware func(string, endpoint.Endpoint) endpoint.Endpoint
 
 // WrapAllLabeledExcept wraps each Endpoint field of struct Endpoints with a
-// LabeledMiddleware, which will receive the name of the handler. See
+// LabeledMiddleware, which will receive the name of the endpoint. See
 // LabeldMiddleware. See method WrapAllExept for details on excluded
 // functionality.
 func (e *Endpoints) WrapAllLabeledExcept(middleware LabeledMiddleware, excluded ...string) {