admin,templates,core: Minor enhancements and error handling (#3607)

* fix 2 possible bugs

* handle unhandled errors

admin.go

@@ -18,6 +18,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"expvar"
 	"fmt"
 	"io"
@@ -235,15 +236,20 @@ func replaceAdmin(cfg *Config) error {
 		MaxHeaderBytes:    1024 * 64,
 	}
 
-	go adminServer.Serve(ln)
+	adminLogger := Log().Named("admin")
+	go func() {
+		if err := adminServer.Serve(ln); !errors.Is(err, http.ErrServerClosed) {
+			adminLogger.Error("admin server shutdown for unknown reason", zap.Error(err))
+		}
+	}()
 
-	Log().Named("admin").Info("admin endpoint started",
+	adminLogger.Info("admin endpoint started",
 		zap.String("address", addr.String()),
 		zap.Bool("enforce_origin", adminConfig.EnforceOrigin),
 		zap.Strings("origins", handler.allowedOrigins))
 
 	if !handler.enforceHost {
-		Log().Named("admin").Warn("admin endpoint on open interface; host checking disabled",
+		adminLogger.Warn("admin endpoint on open interface; host checking disabled",
 			zap.String("address", addr.String()))
 	}
 

caddy.go

@@ -471,7 +471,7 @@ func stopAndCleanup() error {
 	}
 	certmagic.CleanUpOwnLocks()
 	if pidfile != "" {
-		os.Remove(pidfile)
+		return os.Remove(pidfile)
 	}
 	return nil
 }

modules/caddyhttp/reverseproxy/selectionpolicies.go

@@ -401,6 +401,9 @@ func leastRequests(upstreams []*Upstream) *Upstream {
 			best = append(best, upstream)
 		}
 	}
+	if len(best) == 0 {
+		return nil
+	}
 	return best[weakrand.Intn(len(best))]
 }
 

modules/caddyhttp/templates/tplcontext_test.go

@@ -90,7 +90,7 @@ func TestCookie(t *testing.T) {
 		},
 		{
 			// cookie with optional fields
-			cookie:     &http.Cookie{Name: "cookie", Value: "cookieValue", Path: "/path", Domain: "https://localhost", Expires: (time.Now().Add(10 * time.Minute)), MaxAge: 120},
+			cookie:     &http.Cookie{Name: "cookie", Value: "cookieValue", Path: "/path", Domain: "https://localhost", Expires: time.Now().Add(10 * time.Minute), MaxAge: 120},
 			cookieName: "cookie",
 			expect:     "cookieValue",
 		},