Clear up old Actions logs (#31735)

Part of #24256.

Clear up old action logs to free up storage space.

Users will see a message indicating that the log has been cleared if
they view old tasks.

<img width="1361" alt="image"
src="https://github.com/user-attachments/assets/9f0f3a3a-bc5a-402f-90ca-49282d196c22">

Docs: https://gitea.com/gitea/docs/pulls/40

---------

Co-authored-by: silverwind <me@silverwind.io>
(cherry picked from commit 687c1182482ad9443a5911c068b317a91c91d586)

Conflicts:
	custom/conf/app.example.ini
	routers/web/repo/actions/view.go
  trivial context conflict

models/actions/task.go

@@ -35,7 +35,7 @@ type ActionTask struct {
 	RunnerID int64              `xorm:"index"`
 	Status   Status             `xorm:"index"`
 	Started  timeutil.TimeStamp `xorm:"index"`
-	Stopped  timeutil.TimeStamp
+	Stopped  timeutil.TimeStamp `xorm:"index(stopped_log_expired)"`
 
 	RepoID            int64  `xorm:"index"`
 	OwnerID           int64  `xorm:"index"`
@@ -51,8 +51,8 @@ type ActionTask struct {
 	LogInStorage bool       // read log from database or from storage
 	LogLength    int64      // lines count
 	LogSize      int64      // blob size
-	LogIndexes   LogIndexes `xorm:"LONGBLOB"` // line number to offset
-	LogExpired   bool       // files that are too old will be deleted
+	LogIndexes   LogIndexes `xorm:"LONGBLOB"`                   // line number to offset
+	LogExpired   bool       `xorm:"index(stopped_log_expired)"` // files that are too old will be deleted
 
 	Created timeutil.TimeStamp `xorm:"created"`
 	Updated timeutil.TimeStamp `xorm:"updated index"`
@@ -470,6 +470,16 @@ func StopTask(ctx context.Context, taskID int64, status Status) error {
 	return nil
 }
 
+func FindOldTasksToExpire(ctx context.Context, olderThan timeutil.TimeStamp, limit int) ([]*ActionTask, error) {
+	e := db.GetEngine(ctx)
+
+	tasks := make([]*ActionTask, 0, limit)
+	// Check "stopped > 0" to avoid deleting tasks that are still running
+	return tasks, e.Where("stopped > 0 AND stopped < ? AND log_expired = ?", olderThan, false).
+		Limit(limit).
+		Find(&tasks)
+}
+
 func isSubset(set, subset []string) bool {
 	m := make(container.Set[string], len(set))
 	for _, v := range set {

models/migrations/migrations.go

@@ -597,6 +597,8 @@ var migrations = []Migration{
 	NewMigration("Add force-push branch protection support", v1_23.AddForcePushBranchProtection),
 	// v301 -> v302
 	NewMigration("Add skip_secondary_authorization option to oauth2 application table", v1_23.AddSkipSecondaryAuthColumnToOAuth2ApplicationTable),
+	// v302 -> v303
+	NewMigration("Add index to action_task stopped log_expired", v1_23.AddIndexToActionTaskStoppedLogExpired),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v1_23/v302.go

@@ -0,0 +1,18 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_23 //nolint
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func AddIndexToActionTaskStoppedLogExpired(x *xorm.Engine) error {
+	type ActionTask struct {
+		Stopped    timeutil.TimeStamp `xorm:"index(stopped_log_expired)"`
+		LogExpired bool               `xorm:"index(stopped_log_expired)"`
+	}
+	return x.Sync(new(ActionTask))
+}