feat: add OTEL HTTP tracing middleware

go.mod

@@ -42,6 +42,7 @@ require (
 	github.com/prometheus/client_golang v1.19.1
 	github.com/redis/go-redis/v9 v9.18.0
 	github.com/stripe/stripe-go/v82 v82.5.1
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.65.0
 	go.opentelemetry.io/otel v1.40.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.40.0
 	go.opentelemetry.io/otel/sdk v1.40.0
@@ -184,7 +185,6 @@ require (
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/detectors/gcp v1.39.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.63.0 // indirect
-	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.65.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.40.0 // indirect
 	go.opentelemetry.io/otel/metric v1.40.0 // indirect
 	go.opentelemetry.io/otel/sdk/metric v1.40.0 // indirect

module/http_middleware_otel.go

@@ -0,0 +1,47 @@
+package module
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/CrisisTextLine/modular"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
+)
+
+// OTelMiddleware instruments HTTP requests with OpenTelemetry tracing.
+type OTelMiddleware struct {
+	name       string
+	serverName string
+}
+
+// NewOTelMiddleware creates a new OpenTelemetry HTTP tracing middleware.
+func NewOTelMiddleware(name, serverName string) *OTelMiddleware {
+	return &OTelMiddleware{name: name, serverName: serverName}
+}
+
+// Name returns the module name.
+func (m *OTelMiddleware) Name() string { return m.name }
+
+// Init initializes the middleware.
+func (m *OTelMiddleware) Init(_ modular.Application) error { return nil }
+
+// Process wraps the handler with OpenTelemetry HTTP instrumentation.
+func (m *OTelMiddleware) Process(next http.Handler) http.Handler {
+	return otelhttp.NewHandler(next, m.serverName)
+}
+
+// ProvidesServices returns the services provided by this middleware.
+func (m *OTelMiddleware) ProvidesServices() []modular.ServiceProvider {
+	return []modular.ServiceProvider{
+		{Name: m.name, Description: "OpenTelemetry HTTP Tracing Middleware", Instance: m},
+	}
+}
+
+// RequiresServices returns services required by this middleware.
+func (m *OTelMiddleware) RequiresServices() []modular.ServiceDependency { return nil }
+
+// Start is a no-op for this middleware.
+func (m *OTelMiddleware) Start(_ context.Context) error { return nil }
+
+// Stop is a no-op for this middleware.
+func (m *OTelMiddleware) Stop(_ context.Context) error { return nil }

module/http_middleware_otel_test.go

@@ -0,0 +1,76 @@
+package module
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestNewOTelMiddleware(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	if m.Name() != "otel-mw" {
+		t.Errorf("expected name 'otel-mw', got %q", m.Name())
+	}
+}
+
+func TestOTelMiddleware_Init(t *testing.T) {
+	app := CreateIsolatedApp(t)
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	if err := m.Init(app); err != nil {
+		t.Fatalf("Init failed: %v", err)
+	}
+}
+
+func TestOTelMiddleware_Process_CallsNext(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+
+	nextCalled := false
+	handler := m.Process(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		nextCalled = true
+		w.WriteHeader(http.StatusOK)
+	}))
+
+	req := httptest.NewRequest("GET", "/test", nil)
+	rec := httptest.NewRecorder()
+	handler.ServeHTTP(rec, req)
+
+	if !nextCalled {
+		t.Error("expected next handler to be called")
+	}
+	if rec.Code != http.StatusOK {
+		t.Errorf("expected 200, got %d", rec.Code)
+	}
+}
+
+func TestOTelMiddleware_ProvidesServices(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	svcs := m.ProvidesServices()
+	if len(svcs) != 1 {
+		t.Fatalf("expected 1 service, got %d", len(svcs))
+	}
+	if svcs[0].Name != "otel-mw" {
+		t.Errorf("expected service name 'otel-mw', got %q", svcs[0].Name)
+	}
+}
+
+func TestOTelMiddleware_RequiresServices(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	if m.RequiresServices() != nil {
+		t.Error("expected nil dependencies")
+	}
+}
+
+func TestOTelMiddleware_Start(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	if err := m.Start(context.TODO()); err != nil {
+		t.Fatalf("Start failed: %v", err)
+	}
+}
+
+func TestOTelMiddleware_Stop(t *testing.T) {
+	m := NewOTelMiddleware("otel-mw", "workflow-http")
+	if err := m.Stop(context.TODO()); err != nil {
+		t.Fatalf("Stop failed: %v", err)
+	}
+}

plugins/observability/modules.go

@@ -16,6 +16,7 @@ func moduleFactories() map[string]plugin.ModuleFactory {
 		"log.collector":      logCollectorFactory,
 		"observability.otel": otelTracingFactory,
 		"openapi.generator":  openAPIGeneratorFactory,
+		"http.middleware.otel": otelMiddlewareFactory,
 	}
 }
 
@@ -116,3 +117,11 @@ func openAPIGeneratorFactory(name string, cfg map[string]any) modular.Module {
 	}
 	return module.NewOpenAPIGenerator(name, genConfig)
 }
+
+func otelMiddlewareFactory(name string, cfg map[string]any) modular.Module {
+	serverName := "workflow-http"
+	if v, ok := cfg["serverName"].(string); ok && v != "" {
+		serverName = v
+	}
+	return module.NewOTelMiddleware(name, serverName)
+}

plugins/observability/plugin.go

@@ -36,6 +36,7 @@ func New() *ObservabilityPlugin {
 				"log.collector",
 				"observability.otel",
 				"openapi.generator",
+				"http.middleware.otel",
 			},
 			WiringHooks: []string{
 				"observability.health-endpoints",

plugins/observability/schemas.go

@@ -76,5 +76,15 @@ func moduleSchemas() []*schema.ModuleSchema {
 			},
 			DefaultConfig: map[string]any{"title": "Workflow API", "version": "1.0.0"},
 		},
+		{
+			Type:        "http.middleware.otel",
+			Label:       "OTEL HTTP Middleware",
+			Category:    "observability",
+			Description: "Instruments HTTP requests with OpenTelemetry tracing spans",
+			ConfigFields: []schema.ConfigFieldDef{
+				{Key: "serverName", Label: "Server Name", Type: schema.FieldTypeString, DefaultValue: "workflow-http", Description: "Server name used as the span operation name", Placeholder: "workflow-http"},
+			},
+			DefaultConfig: map[string]any{"serverName": "workflow-http"},
+		},
 	}
 }