feat: add OpenTracing middleware

README.md

@@ -26,6 +26,7 @@ Features include:
   - Automatic recovery from panics with traceback & request logging
   - Structured logging middleware using [Zap](https://github.com/uber-go/zap)
   - Automatic handling of `Prefer: return=minimal` from [RFC 7240](https://tools.ietf.org/html/rfc7240#section-4.2)
+  - [OpenTracing](https://opentracing.io/) for requests and errors
 - Per-operation request size limits & timeouts with sane defaults
 - [Content negotiation](https://developer.mozilla.org/en-US/docs/Web/HTTP/Content_negotiation) between server and client
   - Support for gzip ([RFC 1952](https://tools.ietf.org/html/rfc1952)) & Brotli ([RFC 7932](https://tools.ietf.org/html/rfc7932)) content encoding via the `Accept-Encoding` header.
@@ -480,6 +481,30 @@ app.Middleware(func(next http.Handler) http.Handler {
 
 When using the `cli.NewRouter` convenience method, a set of default middleware is added for you. See `middleware.DefaultChain` for more info.
 
+### Enabling OpenTracing
+
+[OpenTracing](https://opentracing.io/) support is built-in, but you have to tell the global tracer where to send the information, otherwise it acts as a no-op. For example, if you use [DataDog APM](https://www.datadoghq.com/blog/opentracing-datadog-cncf/) and have the agent configured wherever you deploy your service:
+
+```go
+import (
+	"github.com/opentracing/opentracing-go"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+)
+
+func main() {
+	t := opentracer.New(tracer.WithAgentAddr("host:port"))
+	defer tracer.Stop()
+
+	// Set it as a Global Tracer
+	opentracing.SetGlobalTracer(t)
+
+	app := cli.NewRouter("My Cool Service", "1.0.0")
+	// register routes here
+	app.Run()
+}
+```
+
 ### Timeouts, Deadlines, Cancellation & Limits
 
 Huma provides utilities to prevent long-running handlers and issues with huge request bodies and slow clients with sane defaults out of the box.

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/magiconair/properties v1.8.2 // indirect
 	github.com/mattn/go-isatty v0.0.12
 	github.com/mitchellh/mapstructure v1.3.3 // indirect
+	github.com/opentracing/opentracing-go v1.2.0
 	github.com/pelletier/go-toml v1.8.0 // indirect
 	github.com/spf13/afero v1.3.4 // indirect
 	github.com/spf13/cast v1.3.1 // indirect

go.sum

@@ -171,6 +171,8 @@ github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJ
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
 github.com/oklog/ulid v1.3.1/go.mod h1:CirwcVhetQ6Lv90oh/F+FBtV6XMibvdAFo93nm5qn4U=
+github.com/opentracing/opentracing-go v1.2.0 h1:uEJPy/1a5RIPAJ0Ov+OIO8OxWu77jEv+1B0VhjKrZUs=
+github.com/opentracing/opentracing-go v1.2.0/go.mod h1:GxEUsuufX4nBwe+T+Wl9TAgYrxe9dPLANfrWvHYVTgc=
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pelletier/go-toml v1.2.0 h1:T5zMGML61Wp+FlcbWjRDT7yAxhJNAiPPLOFECq181zc=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=

middleware/middleware.go

@@ -23,6 +23,7 @@ func DefaultChain(next http.Handler) http.Handler {
 	// Note: logger goes before recovery so that recovery can use it. We don't
 	// expect the logger to cause panics.
 	return chi.Chain(
+		OpenTracing,
 		Logger,
 		Recovery,
 		ContentEncoding,

middleware/opentracing.go

@@ -0,0 +1,41 @@
+package middleware
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+)
+
+// OpenTracing provides a middleware for cross-service tracing support.
+func OpenTracing(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		tracer := opentracing.GlobalTracer()
+
+		// Get any incoming tracing context via HTTP headers & create the span.
+		ctx, _ := tracer.Extract(opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(r.Header))
+		span := tracer.StartSpan("http.request", ext.RPCServerOption(ctx))
+		defer span.Finish()
+
+		// Set basic HTTP info
+		ext.HTTPMethod.Set(span, r.Method)
+		ext.HTTPUrl.Set(span, r.URL.String())
+		ext.Component.Set(span, "huma")
+		span.SetTag("span.type", "web")
+
+		// Update context & continue the middleware chain.
+		r = r.WithContext(opentracing.ContextWithSpan(r.Context(), span))
+		ws := statusRecorder{ResponseWriter: w}
+		next.ServeHTTP(&ws, r)
+
+		// If we have a Chi route template, save it
+		if chictx := chi.RouteContext(r.Context()); chictx != nil {
+			span.SetTag("resource.name", chictx.RoutePattern())
+			span.SetOperationName(r.Method + " " + chictx.RoutePattern())
+		}
+
+		// Save the status code
+		ext.HTTPStatusCode.Set(span, uint16(ws.status))
+	})
+}

middleware/recovery.go

@@ -12,6 +12,8 @@ import (
 
 	"github.com/danielgtaylor/huma"
 	"github.com/go-chi/chi"
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
 	"go.uber.org/zap"
 )
 
@@ -110,6 +112,11 @@ func Recovery(next http.Handler) http.Handler {
 					fmt.Printf("Caught panic: %v\n%s\n\nFrom request:\n%s", err, debug.Stack(), string(request))
 				}
 
+				// If OpenTracing is enabled, augment the span with error info
+				if span := opentracing.SpanFromContext(r.Context()); span != nil {
+					span.SetTag(string(ext.Error), err)
+				}
+
 				ctx := huma.ContextFromRequest(w, r)
 				ctx.WriteError(http.StatusInternalServerError, "Unrecoverable internal server error")
 			}