Add metrics middleware and wire into API

Introduce business/web/v1/mid/metrics.go to track requests, errors,
panics and goroutine samples. Call metrics.AddPanics in the Panics
middleware and include mid.Metrics() in APIMux. Update hack handler to
return an HTTP 400 response error using response.NewError. Add a
Makefile 'load' target to run hey load tests

Author: standard-librarian

app/services/sales-api/v1/handlers/hackgrp/hackgrp.go

@@ -2,16 +2,19 @@ package hackgrp
 
 import (
 	"context"
+	"errors"
 	"math/rand"
 	"net/http"
 
+	"github.com/standard-librarian/gosale/business/web/v1/response"
 	"github.com/standard-librarian/gosale/foundation/web"
 )
 
 func Hack(ctx context.Context, w http.ResponseWriter, r *http.Request) error {
-	if n := rand.Intn(2); n == 0 {
-		return web.NewShutdownError("hack group initiated shutdown")
+	if n := rand.Intn(100) % 2; n == 0 {
+		return response.NewError(errors.New("TRUST ERROR"), http.StatusBadRequest)
 	}
+
 	status := struct {
 		Status string
 	}{

business/web/v1/mid/metrics.go

@@ -0,0 +1,35 @@
+package mid
+
+import (
+	"context"
+	"net/http"
+
+	metrics "github.com/standard-librarian/gosale/business/web/v1/mertrics"
+	"github.com/standard-librarian/gosale/foundation/web"
+)
+
+// Metrics updates program counters.
+func Metrics() web.Middleware {
+	m := func(handler web.Handler) web.Handler {
+		h := func(ctx context.Context, w http.ResponseWriter, r *http.Request) error {
+			ctx = metrics.Set(ctx)
+
+			err := handler(ctx, w, r)
+
+			n := metrics.AddRequests(ctx)
+			if n%1000 == 0 {
+				metrics.AddGoroutines(ctx)
+			}
+
+			if err != nil {
+				metrics.AddErrors(ctx)
+			}
+
+			return err
+		}
+
+		return h
+	}
+
+	return m
+}

business/web/v1/mid/panics.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"runtime/debug"
 
+	metrics "github.com/standard-librarian/gosale/business/web/v1/mertrics"
 	"github.com/standard-librarian/gosale/foundation/web"
 )
 
@@ -22,7 +23,7 @@ func Panics() web.Middleware {
 					trace := debug.Stack()
 					err = fmt.Errorf("PANIC [%v] TRACE[%s]", rec, string(trace))
 
-					// metrics.AddPanics(ctx)
+					metrics.AddPanics(ctx)
 				}
 			}()
 

business/web/v1/v1.go

@@ -23,7 +23,7 @@ type RouteAdder interface {
 
 // APIMux constructs a http.Handler with all application routes defined.
 func APIMux(cfg APIMuxConfig, routeAdder RouteAdder) *web.App {
-	app := web.NewApp(cfg.Shutdown, mid.Logger(cfg.Log), mid.Errors(cfg.Log), mid.Panics())
+	app := web.NewApp(cfg.Shutdown, mid.Logger(cfg.Log), mid.Errors(cfg.Log), mid.Metrics(), mid.Panics())
 
 	routeAdder.Add(app, cfg)
 

makefile

@@ -11,6 +11,9 @@ run-help:
 curl:
 	curl -il http://localhost:3000/hack
 
+load:
+	hey -m GET -c 100 -n 100000 "http://localhost:3000/hack"
+
 # ==============================================================================
 # Define dependencies