From c7c9706d7cf094e827b411f6d7b26eb4f6c14e8a Mon Sep 17 00:00:00 2001
From: Bram Schuur <bschuur@stackstate.com>
Date: Tue, 20 Aug 2024 16:45:15 +0200
Subject: [PATCH] STAC-21470: Forward request even on panic

---
 internal/mirror/reflector.go |  2 +-
 internal/mirror/sendqueue.go |  6 +++---
 internal/proxy/handler.go    | 12 ++++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/internal/mirror/reflector.go b/internal/mirror/reflector.go
index 68e854a..832f49d 100644
--- a/internal/mirror/reflector.go
+++ b/internal/mirror/reflector.go
@@ -68,7 +68,7 @@ func (r *Reflector) sendToMirrors(req *Request) {
 	defer r.RUnlock()
 
 	for _, mirror := range r.mirrors {
-		go mirror.Reflect(req)
+		mirror.Reflect(req)
 	}
 }
 
diff --git a/internal/mirror/sendqueue.go b/internal/mirror/sendqueue.go
index 2935747..4f00ab3 100644
--- a/internal/mirror/sendqueue.go
+++ b/internal/mirror/sendqueue.go
@@ -66,12 +66,12 @@ func (s *SendQueue) AddToQueue(req *Request, targetURL string) {
 }
 
 func (s *SendQueue) NextExecuteItems() []*Request {
-	var result []*Request
-	var newQueue []*Request
-
 	s.Lock()
 	defer s.Unlock()
 
+	var result []*Request
+	var newQueue []*Request = make([]*Request, 0, len(s.requestsQueued))
+
 	// Try to find the next request that can execute, assumes
 	for _, request := range s.requestsQueued {
 		// Try to figure out whether the completed epoch have advanced enough for the request to be picked up.
diff --git a/internal/proxy/handler.go b/internal/proxy/handler.go
index 8abfa6d..1308911 100644
--- a/internal/proxy/handler.go
+++ b/internal/proxy/handler.go
@@ -33,6 +33,18 @@ func ReverseProxyHandler(reflector *mirror.Reflector, url *url.URL) func(res htt
 		requestEpoch := epoch.Add(1)
 		activeRequests.Set(requestEpoch, nil)
 
+		// Catch panic in serving HTTP
+		defer func() {
+			if p := recover(); p != nil {
+				// At this point the request has been served to the main target, so we remove this as active request
+				activeRequests.Remove(requestEpoch)
+
+				reflector.IncomingCh <- mirror.NewRequest(req, body, requestEpoch, activeSnapshot)
+
+				panic(p)
+			}
+		}()
+
 		// Server the request to main target
 		proxyTo.ServeHTTP(res, req)