reverseproxy: Implement health_follow_redirects (#6302)

* added health_follow_redirect in active health checks

* chore: code format

* chore: refactore reversproxy healthcheck redirect variable name and description of the same

* chore: formatting

* changed reverse proxy health check status code range to be between 200-299

* chore: formatting

---------

Co-authored-by: aliasgar <[email protected]>

1 files changed, 10 insertions, 1 deletions

diff --git a/modules/caddyhttp/reverseproxy/healthchecks.go b/modules/caddyhttp/reverseproxy/healthchecks.go
index 507e67c88..90db9b340 100644
--- a/modules/caddyhttp/reverseproxy/healthchecks.go
+++ b/modules/caddyhttp/reverseproxy/healthchecks.go
@@ -82,6 +82,9 @@ type ActiveHealthChecks struct {
 	// HTTP headers to set on health check requests.
 	Headers http.Header `json:"headers,omitempty"`
 
+	// Whether to follow HTTP redirects in response to active health checks (default off).
+	FollowRedirects bool `json:"follow_redirects,omitempty"`
+
 	// How frequently to perform active health checks (default 30s).
 	Interval caddy.Duration `json:"interval,omitempty"`
 
@@ -153,6 +156,12 @@ func (a *ActiveHealthChecks) Provision(ctx caddy.Context, h *Handler) error {
 	a.httpClient = &http.Client{
 		Timeout:   timeout,
 		Transport: h.Transport,
+		CheckRedirect: func(req *http.Request, via []*http.Request) error {
+			if !a.FollowRedirects {
+				return http.ErrUseLastResponse
+			}
+			return nil
+		},
 	}
 
 	for _, upstream := range h.Upstreams {
@@ -453,7 +462,7 @@ func (h *Handler) doActiveHealthCheck(dialInfo DialInfo, hostAddr string, upstre
 			markUnhealthy()
 			return nil
 		}
-	} else if resp.StatusCode < 200 || resp.StatusCode >= 400 {
+	} else if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		h.HealthChecks.Active.logger.Info("status code out of tolerances",
 			zap.Int("status_code", resp.StatusCode),
 			zap.String("host", hostAddr),