internal/ratelimiter/middleware.go

package ratelimiter

import (
	"net/http"

	"github.com/sirupsen/logrus"

	"gitlab.com/gitlab-org/gitlab-pages/internal/httperrors"
	"gitlab.com/gitlab-org/gitlab-pages/internal/logging"
	"gitlab.com/gitlab-org/gitlab-pages/internal/request"
)

const (
	headerGitLabRealIP    = "GitLab-Real-IP"
	headerXForwardedFor   = "X-Forwarded-For"
	headerXForwardedProto = "X-Forwarded-Proto"
)

// Middleware returns middleware for rate-limiting clients
func (rl *RateLimiter) Middleware(handler http.Handler) http.Handler {
	if rl.limitPerSecond <= 0.0 {
		return handler
	}

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if rl.requestAllowed(r) {
			handler.ServeHTTP(w, r)
			return
		}

		if rl.blockedCount != nil {
			rl.blockedCount.WithLabelValues(rl.name).Inc()
		}

		if rl.closeConnection {
			logging.LogRequest(r).Info("request hit rate limit, adding Connection close header in the response.")
			w.Header().Set("Connection", "close")
		}

		rl.logRateLimitedRequest(r)

		httperrors.Serve429(w)
	})
}

func (rl *RateLimiter) logRateLimitedRequest(r *http.Request) {
	logging.LogRequest(r).WithFields(logrus.Fields{
		"rate_limiter_name":             rl.name,
		"scheme":                        r.URL.Scheme,
		"remote_addr":                   r.RemoteAddr,
		"source_ip":                     request.GetIPV4orIPV6PrefixWithoutPort(r),
		"x_forwarded_proto":             r.Header.Get(headerXForwardedProto),
		"x_forwarded_for":               r.Header.Get(headerXForwardedFor),
		"gitlab_real_ip":                r.Header.Get(headerGitLabRealIP),
		"rate_limiter_limit_per_second": rl.limitPerSecond,
		"rate_limiter_burst_size":       rl.burstSize,
		"close_connection":              rl.closeConnection,
	}). // TODO: change to Debug with https://gitlab.com/gitlab-org/gitlab-pages/-/issues/629
		Info("request hit rate limit")
}