traefik/middlewares/empty_backend_handler.go

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2017-07-10 10:11:44 +00:00
package middlewares
import (
"net/http"
"github.com/containous/traefik/healthcheck"
)
// EmptyBackendHandler is a middlware that checks whether the current Backend
// has at least one active Server in respect to the healthchecks and if this
// is not the case, it will stop the middleware chain and respond with 503.
type EmptyBackendHandler struct {
lb healthcheck.LoadBalancer
next http.Handler
}
// NewEmptyBackendHandler creates a new EmptyBackendHandler instance.
func NewEmptyBackendHandler(lb healthcheck.LoadBalancer, next http.Handler) *EmptyBackendHandler {
return &EmptyBackendHandler{lb: lb, next: next}
}
// ServeHTTP responds with 503 when there is no active Server and otherwise
// invokes the next handler in the middleware chain.
func (h *EmptyBackendHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
if len(h.lb.Servers()) == 0 {
rw.WriteHeader(http.StatusServiceUnavailable)
rw.Write([]byte(http.StatusText(http.StatusServiceUnavailable)))
} else {
h.next.ServeHTTP(rw, r)
}
}