add cannary info to access log.

pkg/middlewares/canary/canary.go

@@ -13,6 +13,7 @@ import (
 	"github.com/containous/traefik/v2/pkg/config/dynamic"
 	"github.com/containous/traefik/v2/pkg/log"
 	"github.com/containous/traefik/v2/pkg/middlewares"
+	"github.com/containous/traefik/v2/pkg/middlewares/accesslog"
 	"github.com/containous/traefik/v2/pkg/tracing"
 	"github.com/opentracing/opentracing-go/ext"
 )
@@ -81,6 +82,15 @@ func (c *Canary) GetTracingInformation() (string, ext.SpanKindEnum) {
 func (c *Canary) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 	c.processRequestID(rw, req)
 	c.processCanary(rw, req)
+
+	if logData := accesslog.GetLogData(req); logData != nil {
+		if requestID := req.Header.Get(headerXRequestID); requestID != "" {
+			logData.Core["XRequestID"] = requestID
+		}
+		if xCanary := req.Header.Values(headerXCanary); len(xCanary) > 0 {
+			logData.Core["XCanary"] = xCanary
+		}
+	}
 	c.next.ServeHTTP(rw, req)
 }