traefik/pkg/middlewares/tracing/wrapper.go

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