Add Middleware Support

TODO.md

@@ -1,6 +1,6 @@
 # TODO
 
-- [ ] Pattern for extending config
+- [x] Pattern for extending config
 
 ## Done
 - [x] Unit tests

go.mod

@@ -30,7 +30,7 @@ require (
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.25.1 // indirect
 	github.com/klauspost/compress v1.17.11 // indirect
-	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/prometheus/client_model v0.6.1 // indirect
@@ -38,12 +38,12 @@ require (
 	github.com/prometheus/procfs v0.15.1 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.33.0 // indirect
-	go.opentelemetry.io/proto/otlp v1.4.0 // indirect
+	go.opentelemetry.io/proto/otlp v1.5.0 // indirect
-	golang.org/x/net v0.33.0 // indirect
+	golang.org/x/net v0.34.0 // indirect
 	golang.org/x/sys v0.29.0 // indirect
 	golang.org/x/text v0.21.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20250102185135-69823020774d // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20250106144421-5f5ef82da422 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20250102185135-69823020774d // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20250106144421-5f5ef82da422 // indirect
 	google.golang.org/grpc v1.69.2 // indirect
-	google.golang.org/protobuf v1.36.1 // indirect
+	google.golang.org/protobuf v1.36.2 // indirect
 )

go.sum

@@ -35,6 +35,8 @@ github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
 github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
+github.com/mattn/go-colorable v0.1.14/go.mod h1:6LmQG8QLFO4G5z1gPvYEzlUgJ2wF+stgPZH1UqBm1s8=
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
 github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
@@ -87,10 +89,14 @@ go.opentelemetry.io/otel/trace v1.33.0 h1:cCJuF7LRjUFso9LPnEAHJDB2pqzp+hbO8eu1qq
 go.opentelemetry.io/otel/trace v1.33.0/go.mod h1:uIcdVUZMpTAmz0tI1z04GoVSezK37CbGV4fr1f2nBck=
 go.opentelemetry.io/proto/otlp v1.4.0 h1:TA9WRvW6zMwP+Ssb6fLoUIuirti1gGbP28GcKG1jgeg=
 go.opentelemetry.io/proto/otlp v1.4.0/go.mod h1:PPBWZIP98o2ElSqI35IHfu7hIhSwvc5N38Jw8pXuGFY=
+go.opentelemetry.io/proto/otlp v1.5.0 h1:xJvq7gMzB31/d406fB8U5CBdyQGw4P399D1aQWU/3i4=
+go.opentelemetry.io/proto/otlp v1.5.0/go.mod h1:keN8WnHxOy8PG0rQZjJJ5A2ebUoafqWp0eVQ4yIXvJ4=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 golang.org/x/net v0.33.0 h1:74SYHlV8BIgHIFC/LrYkOGIwL19eTYXQ5wc6TBuO36I=
 golang.org/x/net v0.33.0/go.mod h1:HXLR5J+9DxmrqMwG9qjGCxZ+zKXxBru04zlTvWlWuN4=
+golang.org/x/net v0.34.0 h1:Mb7Mrk043xzHgnRM88suvJFwzVrRfHEHJEl5/71CKw0=
+golang.org/x/net v0.34.0/go.mod h1:di0qlW3YNM5oh6GqDGQr92MyTozJPmybPK4Ev/Gm31k=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
@@ -100,12 +106,18 @@ golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
 golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 google.golang.org/genproto/googleapis/api v0.0.0-20250102185135-69823020774d h1:H8tOf8XM88HvKqLTxe755haY6r1fqqzLbEnfrmLXlSA=
 google.golang.org/genproto/googleapis/api v0.0.0-20250102185135-69823020774d/go.mod h1:2v7Z7gP2ZUOGsaFyxATQSRoBnKygqVq2Cwnvom7QiqY=
+google.golang.org/genproto/googleapis/api v0.0.0-20250106144421-5f5ef82da422 h1:GVIKPyP/kLIyVOgOnTwFOrvQaQUzOzGMCxgFUOEmm24=
+google.golang.org/genproto/googleapis/api v0.0.0-20250106144421-5f5ef82da422/go.mod h1:b6h1vNKhxaSoEI+5jc3PJUCustfli/mRab7295pY7rw=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20250102185135-69823020774d h1:xJJRGY7TJcvIlpSrN3K6LAWgNFUILlO+OMAqtg9aqnw=
 google.golang.org/genproto/googleapis/rpc v0.0.0-20250102185135-69823020774d/go.mod h1:3ENsm/5D1mzDyhpzeRi1NR784I0BcofWBoSc5QqqMK4=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250106144421-5f5ef82da422 h1:3UsHvIr4Wc2aW4brOaSCmcxh9ksica6fHEr8P1XhkYw=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20250106144421-5f5ef82da422/go.mod h1:3ENsm/5D1mzDyhpzeRi1NR784I0BcofWBoSc5QqqMK4=
 google.golang.org/grpc v1.69.2 h1:U3S9QEtbXC0bYNvRtcoklF3xGtLViumSYxWykJS+7AU=
 google.golang.org/grpc v1.69.2/go.mod h1:vyjdE6jLBI76dgpDojsFGNaHlxdjXN9ghpnd2o7JGZ4=
 google.golang.org/protobuf v1.36.1 h1:yBPeRvTftaleIgM3PZ/WBIZ7XM/eEYAaEyCwvyjq/gk=
 google.golang.org/protobuf v1.36.1/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
+google.golang.org/protobuf v1.36.2 h1:R8FeyR1/eLmkutZOM5CWghmo5itiG9z0ktFlTVLuTmU=
+google.golang.org/protobuf v1.36.2/go.mod h1:9fA7Ob0pmnwhb644+1+CVWFRbNajQ6iRojtC/QF5bRE=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=

pkg/app/app.go

@@ -3,6 +3,7 @@ package app
 import (
 	"context"
 	"errors"
+	"net/http"
 
 	"github.com/rs/zerolog"
 	"go.opentelemetry.io/otel/codes"
@@ -25,6 +26,7 @@ type App struct {
 
 type AppHTTP struct {
 	Funcs        []srv.HTTPFunc
+	Middleware   []http.Handler
 	HealthChecks []srv.HealthCheckFunc
 	httpDone     <-chan interface{}
 }
@@ -78,9 +80,12 @@ func (a *App) MustRun() {
 func (a *App) initHTTP() {
 	var httpShutdown shutdownFunc
 	httpShutdown, a.HTTP.httpDone = srv.MustInitHTTPServer(
-		a.AppContext,
+		&srv.HTTPServerOpts{
-		a.HTTP.Funcs,
+			Ctx:              a.AppContext,
-		a.HTTP.HealthChecks...,
+			HandleFuncs:      a.HTTP.Funcs,
+			Middleware:       a.HTTP.Middleware,
+			HealthCheckFuncs: a.HTTP.HealthChecks,
+		},
 	)
 	a.shutdownFuncs = append(a.shutdownFuncs, httpShutdown)
 }

pkg/app/setup.go

@@ -23,3 +23,10 @@ func MustSetupConfigAndLogging(ctx context.Context) context.Context {
 	zerolog.Ctx(ctx).Trace().Any("config", *cfg).Send()
 	return ctx
 }
+
+// Unmarshal config into a custom type
+// Type MUST include *config.AppConfig
+// Stored in context as *config.AppConfig but can be asserted back
+func MustSetupConfigAndLoggingInto[T any](ctx context.Context, into T) (context.Context, T) {
+	return ctx, into
+}

pkg/app/setup_custom.go

@@ -0,0 +1,107 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"reflect"
+
+	"gopkg.in/yaml.v3"
+
+	"gitea.libretechconsulting.com/rmcguire/go-app/pkg/config"
+)
+
+// Used to unmarshal config and environment into a custom type
+// that overloads *config.AppConfig. Will perform normal env
+// substitutions for AppConfig, but env overrides for custom type
+// are up to the caller.
+func MustLoadConfigInto[T any](ctx context.Context, into T) (context.Context, T) {
+	// Step 1: Check our custom type for required *config.AppConfig
+	if err := hasAppConfig(into); err != nil {
+		panic(err)
+	}
+
+	// Step 2: Do the normal thing
+	ctx = MustSetupConfigAndLogging(ctx)
+
+	// Step 3: Extract the config
+	cfg := config.MustFromCtx(ctx)
+
+	// Step 4: Unmarshal custom config
+	configPath := flag.Lookup("config")
+	if configPath != nil && configPath.Value.String() != "" {
+		file, err := os.Open(configPath.Value.String())
+		if err != nil {
+			panic(fmt.Errorf("could not open config file: %w", err))
+		}
+		defer file.Close()
+
+		decoder := yaml.NewDecoder(file)
+		if err := decoder.Decode(into); err != nil {
+			panic(fmt.Errorf("could not decode config file: %w", err))
+		}
+	}
+
+	// Step 5: Re-apply AppConfig to custom type
+	if err := setAppConfig(into, cfg); err != nil {
+		panic(err)
+	}
+
+	// Step 6: Update context, return custom type
+	return ctx, into
+}
+
+func setAppConfig[T any](target T, appConfig *config.AppConfig) error {
+	// Ensure target is a pointer to a struct
+	v := reflect.ValueOf(target)
+	if v.Kind() != reflect.Ptr || v.IsNil() {
+		return errors.New("target must be a non-nil pointer to a struct")
+	}
+
+	v = v.Elem() // Dereference the pointer
+	if v.Kind() != reflect.Struct {
+		return errors.New("target must be a pointer to a struct")
+	}
+
+	// Replace *config.AppConfig
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Field(i)
+		if field.Type() == reflect.TypeOf((*config.AppConfig)(nil)) {
+			if !field.CanSet() {
+				return fmt.Errorf("field %q cannot be set", v.Type().Field(i).Name)
+			}
+			field.Set(reflect.ValueOf(appConfig))
+			return nil
+		}
+	}
+
+	return errors.New("no *config.AppConfig field found in target struct")
+}
+
+func hasAppConfig[T any](target T) error {
+	v := reflect.ValueOf(target)
+	if v.Kind() != reflect.Ptr || v.IsNil() {
+		return errors.New("target must be a non-nil pointer to a struct")
+	}
+	v = v.Elem()
+
+	if v.Kind() != reflect.Struct {
+		return errors.New("target must be a pointer to a struct")
+	}
+
+	hasAppConfig := false
+	for i := 0; i < v.NumField(); i++ {
+		field := v.Type().Field(i)
+		if field.Type == reflect.TypeOf((*config.AppConfig)(nil)) {
+			hasAppConfig = true
+			break
+		}
+	}
+	if !hasAppConfig {
+		return errors.New("struct does not contain a *config.AppConfig field")
+	}
+
+	return nil
+}

pkg/otel/otel.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	opentelemetry "go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
 	"go.opentelemetry.io/otel/exporters/prometheus"
@@ -139,7 +140,7 @@ func newPropagator() propagation.TextMapPropagator {
 
 func (s *settings) newTracerProvider(ctx context.Context) (traceProvider *traceSDK.TracerProvider, err error) {
 	traceOpts := []traceSDK.TracerProviderOption{
-		traceSDK.WithResource(newResource()),
+		traceSDK.WithResource(newResource(ctx)),
 	}
 
 	host, set := os.LookupEnv("OTEL_EXPORTER_OTLP_ENDPOINT")
@@ -164,8 +165,15 @@ func (s *settings) newTracerProvider(ctx context.Context) (traceProvider *traceS
 	return
 }
 
-func newResource() *resource.Resource {
+func newResource(ctx context.Context) *resource.Resource {
-	return resource.NewWithAttributes(semconv.SchemaURL)
+	cfg := config.MustFromCtx(ctx)
+	attributes := []attribute.KeyValue{
+		semconv.ServiceName(cfg.Name),
+		semconv.ServiceVersion(cfg.Version),
+		semconv.K8SPodName(os.Getenv("HOSTNAME")),
+	}
+
+	return resource.NewWithAttributes(semconv.SchemaURL, attributes...)
 }
 
 // Configures meter provider
@@ -173,7 +181,9 @@ func newResource() *resource.Resource {
 // Conditionally provides an OTLP metrics exporter
 func (s *settings) newMeterProvider(ctx context.Context) (*metric.MeterProvider, error) {
 	// OTEL Prometheus Exporter
-	exporter, err := prometheus.New()
+	exporter, err := prometheus.New(
+		prometheus.WithResourceAsConstantLabels(attribute.NewDenyKeysFilter()),
+	)
 	if err != nil {
 		return nil, err
 	}
@@ -202,6 +212,7 @@ func (s *settings) newMeterProvider(ctx context.Context) (*metric.MeterProvider,
 	var meterProvider *metric.MeterProvider
 	if otlpExporter != nil {
 		metricOptions = append(metricOptions,
+			metric.WithResource(newResource(ctx)),
 			metric.WithReader(exporter),
 			metric.WithReader(
 				metric.NewPeriodicReader(
@@ -209,12 +220,11 @@ func (s *settings) newMeterProvider(ctx context.Context) (*metric.MeterProvider,
 					metric.WithInterval(s.MetricExportInterval),
 				),
 			),
-			metric.WithResource(newResource()),
 		)
 	} else {
 		metricOptions = append(metricOptions,
+			metric.WithResource(newResource(ctx)),
 			metric.WithReader(exporter),
-			metric.WithResource(newResource()),
 		)
 	}
 

pkg/srv/http.go

@@ -29,10 +29,17 @@ type HTTPFunc struct {
 	HandlerFunc http.HandlerFunc
 }
 
-func prepHTTPServer(ctx context.Context, handleFuncs []HTTPFunc, hcFuncs ...HealthCheckFunc) *http.Server {
+type HTTPServerOpts struct {
+	Ctx              context.Context
+	HandleFuncs      []HTTPFunc
+	Middleware       []http.Handler
+	HealthCheckFuncs []HealthCheckFunc
+}
+
+func prepHTTPServer(opts *HTTPServerOpts) *http.Server {
 	var (
-		cfg = config.MustFromCtx(ctx)
+		cfg = config.MustFromCtx(opts.Ctx)
-		l   = zerolog.Ctx(ctx)
+		l   = zerolog.Ctx(opts.Ctx)
 		mux = &http.ServeMux{}
 	)
 
@@ -43,11 +50,11 @@ func prepHTTPServer(ctx context.Context, handleFuncs []HTTPFunc, hcFuncs ...Heal
 		mux.Handle(pattern, handler) // Associate pattern with handler
 	}
 
-	healthChecks := handleHealthCheckFunc(ctx, hcFuncs...)
+	healthChecks := handleHealthCheckFunc(opts.Ctx, opts.HealthCheckFuncs...)
 	otelHandleFunc("/health", healthChecks)
 	otelHandleFunc("/", healthChecks)
 
-	for _, f := range handleFuncs {
+	for _, f := range opts.HandleFuncs {
 		otelHandleFunc(f.Path, f.HandlerFunc)
 	}
 
@@ -89,9 +96,19 @@ func prepHTTPServer(ctx context.Context, handleFuncs []HTTPFunc, hcFuncs ...Heal
 		idleTimeout = *iT
 	}
 
+	// Inject any supplied middleware
+	for i := len(opts.Middleware) - 1; i >= 0; i-- {
+		mw := opts.Middleware[i]
+		next := handler
+		handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			mw.ServeHTTP(w, r)
+			next.ServeHTTP(w, r)
+		})
+	}
+
 	// Inject logging middleware
 	if cfg.HTTP.LogRequests {
-		handler = loggingMiddleware(ctx, handler)
+		handler = loggingMiddleware(opts.Ctx, handler)
 	}
 
 	return &http.Server{
@@ -101,17 +118,17 @@ func prepHTTPServer(ctx context.Context, handleFuncs []HTTPFunc, hcFuncs ...Heal
 		IdleTimeout:  idleTimeout,
 		Handler:      handler,
 		BaseContext: func(_ net.Listener) context.Context {
-			return ctx
+			return opts.Ctx
 		},
 	}
 }
 
 // Returns a shutdown func and a done channel if the
 // server aborts abnormally. Panics on error.
-func MustInitHTTPServer(ctx context.Context, funcs []HTTPFunc, hcFuncs ...HealthCheckFunc) (
+func MustInitHTTPServer(opts *HTTPServerOpts) (
 	func(context.Context) error, <-chan interface{},
 ) {
-	shutdownFunc, doneChan, err := InitHTTPServer(ctx, funcs, hcFuncs...)
+	shutdownFunc, doneChan, err := InitHTTPServer(opts)
 	if err != nil {
 		panic(err)
 	}
@@ -120,18 +137,18 @@ func MustInitHTTPServer(ctx context.Context, funcs []HTTPFunc, hcFuncs ...Health
 
 // Returns a shutdown func and a done channel if the
 // server aborts abnormally. Returns error on failure to start
-func InitHTTPServer(ctx context.Context, funcs []HTTPFunc, hcFuncs ...HealthCheckFunc) (
+func InitHTTPServer(opts *HTTPServerOpts) (
 	func(context.Context) error, <-chan interface{}, error,
 ) {
-	l := zerolog.Ctx(ctx)
+	l := zerolog.Ctx(opts.Ctx)
 	doneChan := make(chan interface{})
 
 	var server *http.Server
 
-	httpMeter = otel.GetMeter(ctx, "http")
+	httpMeter = otel.GetMeter(opts.Ctx, "http")
-	httpTracer = otel.GetTracer(ctx, "http")
+	httpTracer = otel.GetTracer(opts.Ctx, "http")
 
-	server = prepHTTPServer(ctx, funcs, hcFuncs...)
+	server = prepHTTPServer(opts)
 
 	go func() {
 		l.Debug().Msg("HTTP Server Started")