Add support for filtering request being traced

Author: tigerwill90

foxtrace.go

@@ -3,11 +3,9 @@ package otelfox
 import (
 	"fmt"
 	"github.com/tigerwill90/fox"
-	"go.opentelemetry.io/otel/propagation"
 	semconv "go.opentelemetry.io/otel/semconv/v1.18.0"
 	"go.opentelemetry.io/otel/semconv/v1.18.0/httpconv"
 	"go.opentelemetry.io/otel/trace"
-	"net/http"
 )
 
 const (
@@ -16,11 +14,9 @@ const (
 
 // Tracer is a Fox middleware that traces HTTP requests using OpenTelemetry.
 type Tracer struct {
-	service    string
-	tracer     trace.Tracer
-	propagator propagation.TextMapPropagator
-	carrier    func(r *http.Request) propagation.TextMapCarrier
-	spanFmt    func(r *http.Request) string
+	service string
+	tracer  trace.Tracer
+	cfg     *config
 }
 
 // New creates a new Tracer middleware for the given service.
@@ -33,39 +29,50 @@ func New(service string, opts ...Option) *Tracer {
 
 	tracer := cfg.provider.Tracer(tracerName, trace.WithInstrumentationVersion(SemVersion()))
 	return &Tracer{
-		service:    service,
-		tracer:     tracer,
-		propagator: cfg.propagator,
-		carrier:    cfg.carrier,
-		spanFmt:    cfg.spanFmt,
+		service: service,
+		tracer:  tracer,
+		cfg:     cfg,
 	}
 }
 
+// Middleware is a convenience function that creates a new Tracer middleware instance
+// for the specified service and returns the Trace middleware function.
+// Options can be provided to configure the tracer.
 func Middleware(service string, opts ...Option) fox.MiddlewareFunc {
 	tracer := New(service, opts...)
 	return tracer.Trace
 }
 
+// Trace is a middleware function that wraps the provided HandlerFunc with tracing capabilities.
+// It captures and records HTTP request information using OpenTelemetry.
 func (t *Tracer) Trace(next fox.HandlerFunc) fox.HandlerFunc {
 	return func(c fox.Context) {
 
 		req := c.Request()
-		ctx := t.propagator.Extract(req.Context(), t.carrier(req))
+
+		for _, f := range t.cfg.filters {
+			if !f(req) {
+				next(c)
+				return
+			}
+		}
+
+		ctx := t.cfg.propagator.Extract(req.Context(), t.cfg.carrier(req))
 
 		opts := []trace.SpanStartOption{
 			trace.WithAttributes(httpconv.ServerRequest(t.service, req)...),
 			trace.WithSpanKind(trace.SpanKindServer),
 		}
 
 		var spanName string
-		if t.spanFmt == nil {
+		if t.cfg.spanFmt == nil {
 			spanName = c.Path()
 		} else {
-			spanName = t.spanFmt(req)
+			spanName = t.cfg.spanFmt(req)
 		}
 
 		if spanName == "" {
-			spanName = fmt.Sprintf("HTTP %s route not found", c.Request().Method)
+			spanName = fmt.Sprintf("HTTP %s route not found", req.Method)
 		} else {
 			opts = append(opts, trace.WithAttributes(semconv.HTTPRoute(spanName)))
 		}

go.mod

@@ -4,7 +4,7 @@ go 1.19
 
 require (
 	github.com/stretchr/testify v1.8.2
-	github.com/tigerwill90/fox v0.7.6
+	github.com/tigerwill90/fox v0.8.0
 	go.opentelemetry.io/contrib/propagators/b3 v1.15.0
 	go.opentelemetry.io/otel v1.14.0
 	go.opentelemetry.io/otel/trace v1.14.0

go.sum

@@ -22,8 +22,8 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-github.com/tigerwill90/fox v0.7.6 h1:SuDVuygis0nOcRdmq/dxiJCWhJ33fzh2VwIW7KuKZSA=
-github.com/tigerwill90/fox v0.7.6/go.mod h1:MdAVSWOSSlp+MExhsvqWF1kedhAnMsV90VTcaaQdKWo=
+github.com/tigerwill90/fox v0.8.0 h1:07oGL4H75PR/uK6GIwSSVJpvXYTGr17KPssbSNL7HpA=
+github.com/tigerwill90/fox v0.8.0/go.mod h1:MdAVSWOSSlp+MExhsvqWF1kedhAnMsV90VTcaaQdKWo=
 go.opentelemetry.io/contrib/propagators/b3 v1.15.0 h1:bMaonPyFcAvZ4EVzkUNkfnUHP5Zi63CIDlA3dRsEg8Q=
 go.opentelemetry.io/contrib/propagators/b3 v1.15.0/go.mod h1:VjU0g2v6HSQ+NwfifambSLAeBgevjIcqmceaKWEzl0c=
 go.opentelemetry.io/otel v1.14.0 h1:/79Huy8wbf5DnIPhemGB+zEPVwnN6fuQybr/SRXa6hM=

option.go

@@ -17,11 +17,16 @@ func (o optionFunc) apply(c *config) {
 	o(c)
 }
 
+type Filter func(r *http.Request) bool
+
+type SpanNameFormatter func(r *http.Request) string
+
 type config struct {
 	provider   trace.TracerProvider
 	propagator propagation.TextMapPropagator
 	carrier    func(r *http.Request) propagation.TextMapCarrier
-	spanFmt    func(r *http.Request) string
+	spanFmt    SpanNameFormatter
+	filters    []Filter
 }
 
 func defaultConfig() *config {
@@ -67,8 +72,18 @@ func WithTextMapCarrier(fn func(r *http.Request) propagation.TextMapCarrier) Opt
 
 // WithSpanNameFormatter takes a function that will be called on every request
 // and the returned string will become the Span Name.
-func WithSpanNameFormatter(fn func(r *http.Request) string) Option {
+func WithSpanNameFormatter(fn SpanNameFormatter) Option {
 	return optionFunc(func(c *config) {
 		c.spanFmt = fn
 	})
 }
+
+// WithFilter appends the provided filters to the middleware's filter list.
+// A filter returning false will exclude the request from being traced. If no filters
+// are provided, all requests will be traced. Keep in mind that filters are invoked for each request,
+// so they should be simple and efficient.
+func WithFilter(f ...Filter) Option {
+	return optionFunc(func(c *config) {
+		c.filters = append(c.filters, f...)
+	})
+}