Improve plugin hook cyclic detection (#4625)

* Move and rename HookTriggerEnum into separate package
* Move visited plugin hook handler code
* Allow up to ten plugin hook loops

pkg/plugin/plugins.go

@@ -21,6 +21,7 @@ import (
 	"github.com/stashapp/stash/pkg/logger"
 	"github.com/stashapp/stash/pkg/models"
 	"github.com/stashapp/stash/pkg/plugin/common"
+	"github.com/stashapp/stash/pkg/plugin/hook"
 	"github.com/stashapp/stash/pkg/session"
 	"github.com/stashapp/stash/pkg/sliceutil"
 	"github.com/stashapp/stash/pkg/txn"
@@ -356,7 +357,7 @@ func waitForTask(ctx context.Context, task Task) error {
 	return nil
 }
 
-func (c Cache) ExecutePostHooks(ctx context.Context, id int, hookType HookTriggerEnum, input interface{}, inputFields []string) {
+func (c Cache) ExecutePostHooks(ctx context.Context, id int, hookType hook.TriggerEnum, input interface{}, inputFields []string) {
 	if err := c.executePostHooks(ctx, hookType, common.HookContext{
 		ID:          id,
 		Type:        hookType.String(),
@@ -367,7 +368,7 @@ func (c Cache) ExecutePostHooks(ctx context.Context, id int, hookType HookTrigge
 	}
 }
 
-func (c Cache) RegisterPostHooks(ctx context.Context, id int, hookType HookTriggerEnum, input interface{}, inputFields []string) {
+func (c Cache) RegisterPostHooks(ctx context.Context, id int, hookType hook.TriggerEnum, input interface{}, inputFields []string) {
 	txn.AddPostCommitHook(ctx, func(ctx context.Context) {
 		c.ExecutePostHooks(ctx, id, hookType, input, inputFields)
 	})
@@ -379,23 +380,28 @@ func (c Cache) ExecuteSceneUpdatePostHooks(ctx context.Context, input models.Sce
 		logger.Errorf("error converting id in SceneUpdatePostHooks: %v", err)
 		return
 	}
-	c.ExecutePostHooks(ctx, id, SceneUpdatePost, input, inputFields)
+	c.ExecutePostHooks(ctx, id, hook.SceneUpdatePost, input, inputFields)
 }
 
-func (c Cache) executePostHooks(ctx context.Context, hookType HookTriggerEnum, hookContext common.HookContext) error {
-	visitedPlugins := session.GetVisitedPlugins(ctx)
+// maxCyclicLoopDepth is the maximum number of identical plugin hook calls that
+// can be made before a cyclic loop is detected. It is set to an arbitrary value
+// that should not be hit under normal circumstances.
+const maxCyclicLoopDepth = 10
+
+func (c Cache) executePostHooks(ctx context.Context, hookType hook.TriggerEnum, hookContext common.HookContext) error {
+	visitedPluginHookCounts := getVisitedPluginHookCounts(ctx)
 
 	for _, p := range c.enabledPlugins() {
 		hooks := p.getHooks(hookType)
 		// don't revisit a plugin we've already visited
 		// only log if there's hooks that we're skipping
-		if len(hooks) > 0 && sliceutil.Contains(visitedPlugins, p.id) {
-			logger.Debugf("plugin ID '%s' already triggered, not re-triggering", p.id)
+		if len(hooks) > 0 && visitedPluginHookCounts.For(p.id, hookType) >= maxCyclicLoopDepth {
+			logger.Debugf("cyclic loop detected: plugin ID '%s' hook %s, not re-triggering", p.id, hookType)
 			continue
 		}
 
 		for _, h := range hooks {
-			newCtx := session.AddVisitedPlugin(ctx, p.id)
+			newCtx := session.AddVisitedPluginHook(ctx, p.id, hookType)
 			serverConnection := c.makeServerConnection(newCtx)
 
 			pluginInput := buildPluginInput(&p, &h.OperationConfig, serverConnection, nil)
@@ -434,6 +440,46 @@ func (c Cache) executePostHooks(ctx context.Context, hookType HookTriggerEnum, h
 	return nil
 }
 
+type visitedPluginHookCount struct {
+	session.VisitedPluginHook
+	Count int
+}
+
+type visitedPluginHookCounts []visitedPluginHookCount
+
+func (v visitedPluginHookCounts) For(pluginID string, hookType hook.TriggerEnum) int {
+	for _, c := range v {
+		if c.VisitedPluginHook.PluginID == pluginID && c.VisitedPluginHook.HookType == hookType {
+			return c.Count
+		}
+	}
+	return 0
+}
+
+func getVisitedPluginHookCounts(ctx context.Context) visitedPluginHookCounts {
+	visitedPluginHooks := session.GetVisitedPluginHooks(ctx)
+
+	visitedPluginHookCounts := make([]visitedPluginHookCount, 0)
+	for _, p := range visitedPluginHooks {
+		found := false
+		for i, v := range visitedPluginHookCounts {
+			if v.VisitedPluginHook == p {
+				visitedPluginHookCounts[i].Count++
+				found = true
+				break
+			}
+		}
+		if !found {
+			visitedPluginHookCounts = append(visitedPluginHookCounts, visitedPluginHookCount{
+				VisitedPluginHook: p,
+				Count:             1,
+			})
+		}
+	}
+
+	return visitedPluginHookCounts
+}
+
 func (c Cache) getPlugin(pluginID string) *Config {
 	for _, s := range c.plugins {
 		if s.id == pluginID {