feat: Add *gin.Context Filter parameter (#5743)

Issue:
#3070
last PR status:
#4444

---------

Signed-off-by: Rehan Pasha <[email protected]>
Signed-off-by: Brian Warner <[email protected]>
Signed-off-by: rehanpfmr <[email protected]>
Co-authored-by: Damien Mathieu <[email protected]>

Author: rehanpfmr

CHANGELOG.md

@@ -19,6 +19,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Support for the `OTEL_HTTP_CLIENT_COMPATIBILITY_MODE=http/dup` environment variable in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` to emit attributes for both the v1.20.0 and v1.26.0 semantic conventions. (#5401)
 - The `go.opentelemetry.io/contrib/bridges/otelzerolog` module.
   This module provides an OpenTelemetry logging bridge for `github.com/rs/zerolog`. (#5405)
+- Add `WithGinFilter` filter parameter in `go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin` to allow filtering requests with `*gin.Context`. (#5743)
 
 ### Removed
 

instrumentation/github.com/gin-gonic/gin/otelgin/gintrace.go

@@ -52,6 +52,14 @@ func Middleware(service string, opts ...Option) gin.HandlerFunc {
 				return
 			}
 		}
+		for _, f := range cfg.GinFilters {
+			if !f(c) {
+				// Serve the request to the next middleware
+				// if a filter rejects the request.
+				c.Next()
+				return
+			}
+		}
 		c.Set(tracerKey, tracer)
 		savedCtx := c.Request.Context()
 		defer func() {

instrumentation/github.com/gin-gonic/gin/otelgin/option.go

@@ -8,6 +8,8 @@ package otelgin // import "go.opentelemetry.io/contrib/instrumentation/github.co
 import (
 	"net/http"
 
+	"github.com/gin-gonic/gin"
+
 	"go.opentelemetry.io/otel/propagation"
 	oteltrace "go.opentelemetry.io/otel/trace"
 )
@@ -16,13 +18,18 @@ type config struct {
 	TracerProvider    oteltrace.TracerProvider
 	Propagators       propagation.TextMapPropagator
 	Filters           []Filter
+	GinFilters        []GinFilter
 	SpanNameFormatter SpanNameFormatter
 }
 
 // Filter is a predicate used to determine whether a given http.request should
 // be traced. A Filter must return true if the request should be traced.
 type Filter func(*http.Request) bool
 
+// Adding new Filter parameter (*gin.Context)
+// gin.Context has FullPath() method, which returns a matched route full path.
+type GinFilter func(*gin.Context) bool
+
 // SpanNameFormatter is used to set span name by http.request.
 type SpanNameFormatter func(r *http.Request) string
 
@@ -60,7 +67,7 @@ func WithTracerProvider(provider oteltrace.TracerProvider) Option {
 
 // WithFilter adds a filter to the list of filters used by the handler.
 // If any filter indicates to exclude a request then the request will not be
-// traced. All filters must allow a request to be traced for a Span to be created.
+// traced. All gin and net/http filters must allow a request to be traced for a Span to be created.
 // If no filters are provided then all requests are traced.
 // Filters will be invoked for each processed request, it is advised to make them
 // simple and fast.
@@ -70,6 +77,13 @@ func WithFilter(f ...Filter) Option {
 	})
 }
 
+// WithGinFilter adds a gin filter to the list of filters used by the handler.
+func WithGinFilter(f ...GinFilter) Option {
+	return optionFunc(func(c *config) {
+		c.GinFilters = append(c.GinFilters, f...)
+	})
+}
+
 // WithSpanNameFormatter takes a function that will be called on every
 // request and the returned string will become the Span Name.
 func WithSpanNameFormatter(f func(r *http.Request) string) Option {

instrumentation/github.com/gin-gonic/gin/otelgin/test/gintrace_test.go

@@ -287,3 +287,37 @@ func TestWithFilter(t *testing.T) {
 		assert.Len(t, sr.Ended(), 1)
 	})
 }
+
+func TestWithGinFilter(t *testing.T) {
+	t.Run("custom filter filtering route", func(t *testing.T) {
+		sr := tracetest.NewSpanRecorder()
+		otel.SetTracerProvider(sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr)))
+
+		router := gin.New()
+		f := func(c *gin.Context) bool { return c.Request.URL.Path != "/healthcheck" }
+		router.Use(otelgin.Middleware("foobar", otelgin.WithGinFilter(f)))
+		router.GET("/healthcheck", func(c *gin.Context) {})
+
+		r := httptest.NewRequest("GET", "/healthcheck", nil)
+		w := httptest.NewRecorder()
+
+		router.ServeHTTP(w, r)
+		assert.Len(t, sr.Ended(), 0)
+	})
+
+	t.Run("custom filter not filtering route", func(t *testing.T) {
+		sr := tracetest.NewSpanRecorder()
+		otel.SetTracerProvider(sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(sr)))
+
+		router := gin.New()
+		f := func(c *gin.Context) bool { return c.Request.URL.Path != "/user/:id" }
+		router.Use(otelgin.Middleware("foobar", otelgin.WithGinFilter(f)))
+		router.GET("/user/:id", func(c *gin.Context) {})
+
+		r := httptest.NewRequest("GET", "/user/123", nil)
+		w := httptest.NewRecorder()
+
+		router.ServeHTTP(w, r)
+		assert.Len(t, sr.Ended(), 1)
+	})
+}