package tracing import ( "context" "net/http" "github.com/containous/alice" "github.com/opentracing/opentracing-go/ext" "github.com/traefik/traefik/v2/pkg/log" "github.com/traefik/traefik/v2/pkg/tracing" ) // Traceable embeds tracing information. type Traceable interface { GetTracingInformation() (name string, spanKind ext.SpanKindEnum) } // Wrap adds traceability to an alice.Constructor. func Wrap(ctx context.Context, constructor alice.Constructor) alice.Constructor { return func(next http.Handler) (http.Handler, error) { if constructor == nil { return nil, nil } handler, err := constructor(next) if err != nil { return nil, err } if traceableHandler, ok := handler.(Traceable); ok { name, spanKind := traceableHandler.GetTracingInformation() log.FromContext(ctx).WithField(log.MiddlewareName, name).Debug("Adding tracing to middleware") return NewWrapper(handler, name, spanKind), nil } return handler, nil } } // NewWrapper returns a http.Handler struct. func NewWrapper(next http.Handler, name string, spanKind ext.SpanKindEnum) http.Handler { return &Wrapper{ next: next, name: name, spanKind: spanKind, } } // Wrapper is used to wrap http handler middleware. type Wrapper struct { next http.Handler name string spanKind ext.SpanKindEnum } func (w *Wrapper) ServeHTTP(rw http.ResponseWriter, req *http.Request) { _, err := tracing.FromContext(req.Context()) if err != nil { w.next.ServeHTTP(rw, req) return } var finish func() _, req, finish = tracing.StartSpan(req, w.name, w.spanKind) defer finish() if w.next != nil { w.next.ServeHTTP(rw, req) } }