fixes

pkg/proxy/remotehost.go

@@ -69,7 +69,15 @@ func (m *MockResponseWriter) WriteHeader(statusCode int) {
 	m.StatusCode = statusCode
 }
 
-func NewRemoteHost[V any](host string) (*RemoteHost[V], error) {
+// NewRemoteHost connects to a peer node. httpPort overrides the peer's HTTP
+// port used for request proxying (defaults to "8080"); the gRPC control port
+// is always 1337.
+func NewRemoteHost[V any](host string, httpPort ...string) (*RemoteHost[V], error) {
+
+	port := "8080"
+	if len(httpPort) > 0 && httpPort[0] != "" {
+		port = httpPort[0]
+	}
 
 	target := fmt.Sprintf("%s:1337", host)
 
@@ -85,14 +93,18 @@ func NewRemoteHost[V any](host string) (*RemoteHost[V], error) {
 	transport := &http.Transport{
 		MaxIdleConns:        100,
 		MaxIdleConnsPerHost: 100,
-		DisableKeepAlives:   false,
-		IdleConnTimeout:     120 * time.Second,
+		// Bound concurrently-open connections to this peer so a load spike
+		// can't exhaust file handles. Excess requests wait for a free conn
+		// rather than opening unbounded sockets.
+		MaxConnsPerHost:   256,
+		DisableKeepAlives: false,
+		IdleConnTimeout:   120 * time.Second,
 	}
 	client := &http.Client{Transport: transport, Timeout: 10 * time.Second}
 
 	return &RemoteHost[V]{
 		host:          host,
-		httpBase:      fmt.Sprintf("http://%s:8080", host),
+		httpBase:      fmt.Sprintf("http://%s:%s", host, port),
 		conn:          conn,
 		transport:     transport,
 		client:        client,
@@ -101,6 +113,25 @@ func NewRemoteHost[V any](host string) (*RemoteHost[V], error) {
 	}, nil
 }
 
+// hopByHopHeaders are connection-specific headers that must not be forwarded
+// by a proxy (RFC 7230 §6.1).
+var hopByHopHeaders = map[string]struct{}{
+	"Connection":          {},
+	"Proxy-Connection":    {},
+	"Keep-Alive":          {},
+	"Proxy-Authenticate":  {},
+	"Proxy-Authorization": {},
+	"Te":                  {},
+	"Trailer":             {},
+	"Transfer-Encoding":   {},
+	"Upgrade":             {},
+}
+
+func isHopByHopHeader(key string) bool {
+	_, ok := hopByHopHeaders[http.CanonicalHeaderKey(key)]
+	return ok
+}
+
 func (h *RemoteHost[V]) Name() string {
 	return h.host
 }
@@ -277,6 +308,12 @@ func (h *RemoteHost[V]) Proxy(id uint64, w http.ResponseWriter, r *http.Request,
 	req.Header.Set("X-Forwarded-Host", r.Host)
 
 	for k, v := range r.Header {
+		if isHopByHopHeader(k) {
+			// Don't forward connection-management headers (notably an inbound
+			// "Connection: close" would disable keep-alive on the proxied leg
+			// and churn outbound connections / file handles).
+			continue
+		}
 		for _, vv := range v {
 			req.Header.Add(k, vv)
 		}
@@ -290,6 +327,9 @@ func (h *RemoteHost[V]) Proxy(id uint64, w http.ResponseWriter, r *http.Request,
 	defer res.Body.Close()
 	span.SetAttributes(attribute.Int("status_code", res.StatusCode))
 	for k, v := range res.Header {
+		if isHopByHopHeader(k) {
+			continue
+		}
 		for _, vv := range v {
 			w.Header().Add(k, vv)
 		}