Purge event hooks after USR1 reload, fix #2044 (#2047)

* caddy: Purge event hooks after USR1 reload

* caddy: Remove event hook purge logging

* caddy: Remove deleteEventHook

* caddy: use old event hooks in case of an unsuccessful restart

* caddy: implement restoreEventHooks

plugins.go

@@ -39,7 +39,7 @@ var (
 
 	// eventHooks is a map of hook name to Hook. All hooks plugins
 	// must have a name.
-	eventHooks = sync.Map{}
+	eventHooks = &sync.Map{}
 
 	// parsingCallbacks maps server type to map of directive
 	// to list of callback functions. These aren't really
@@ -271,6 +271,36 @@ func EmitEvent(event EventName, info interface{}) {
 	})
 }
 
+// cloneEventHooks return a clone of the event hooks *sync.Map
+func cloneEventHooks() *sync.Map {
+	c := &sync.Map{}
+	eventHooks.Range(func(k, v interface{}) bool {
+		c.Store(k, v)
+		return true
+	})
+	return c
+}
+
+// purgeEventHooks purges all event hooks from the map
+func purgeEventHooks() {
+	eventHooks.Range(func(k, _ interface{}) bool {
+		eventHooks.Delete(k)
+		return true
+	})
+}
+
+// restoreEventHooks restores eventHooks with a provided *sync.Map
+func restoreEventHooks(m *sync.Map) {
+	// Purge old event hooks
+	purgeEventHooks()
+
+	// Restore event hooks
+	m.Range(func(k, v interface{}) bool {
+		eventHooks.Store(k, v)
+		return true
+	})
+}
+
 // ParsingCallback is a function that is called after
 // a directive's setup functions have been executed
 // for all the server blocks.

sigtrap_posix.go

@@ -76,9 +76,17 @@ func trapSignalsPosix() {
 					caddyfileToUse = newCaddyfile
 				}
 
+				// Backup old event hooks
+				oldEventHooks := cloneEventHooks()
+
+				// Purge the old event hooks
+				purgeEventHooks()
+
 				// Kick off the restart; our work is done
 				_, err = inst.Restart(caddyfileToUse)
 				if err != nil {
+					restoreEventHooks(oldEventHooks)
+
 					log.Printf("[ERROR] SIGUSR1: %v", err)
 				}