Rewrite queue (#24505)

# ⚠️ Breaking

Many deprecated queue config options are removed (actually, they should
have been removed in 1.18/1.19).

If you see the fatal message when starting Gitea: "Please update your
app.ini to remove deprecated config options", please follow the error
messages to remove these options from your app.ini.

Example:

```
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].ISSUE_INDEXER_QUEUE_TYPE`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].UPDATE_BUFFER_LEN`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [F] Please update your app.ini to remove deprecated config options
```

Many options in `[queue]` are are dropped, including:
`WRAP_IF_NECESSARY`, `MAX_ATTEMPTS`, `TIMEOUT`, `WORKERS`,
`BLOCK_TIMEOUT`, `BOOST_TIMEOUT`, `BOOST_WORKERS`, they can be removed
from app.ini.

# The problem

The old queue package has some legacy problems:

* complexity: I doubt few people could tell how it works.
* maintainability: Too many channels and mutex/cond are mixed together,
too many different structs/interfaces depends each other.
* stability: due to the complexity & maintainability, sometimes there
are strange bugs and difficult to debug, and some code doesn't have test
(indeed some code is difficult to test because a lot of things are mixed
together).
* general applicability: although it is called "queue", its behavior is
not a well-known queue.
* scalability: it doesn't seem easy to make it work with a cluster
without breaking its behaviors.

It came from some very old code to "avoid breaking", however, its
technical debt is too heavy now. It's a good time to introduce a better
"queue" package.

# The new queue package

It keeps using old config and concept as much as possible.

* It only contains two major kinds of concepts:
    * The "base queue": channel, levelqueue, redis
* They have the same abstraction, the same interface, and they are
tested by the same testing code.
* The "WokerPoolQueue", it uses the "base queue" to provide "worker
pool" function, calls the "handler" to process the data in the base
queue.
* The new code doesn't do "PushBack"
* Think about a queue with many workers, the "PushBack" can't guarantee
the order for re-queued unhandled items, so in new code it just does
"normal push"
* The new code doesn't do "pause/resume"
* The "pause/resume" was designed to handle some handler's failure: eg:
document indexer (elasticsearch) is down
* If a queue is paused for long time, either the producers blocks or the
new items are dropped.
* The new code doesn't do such "pause/resume" trick, it's not a common
queue's behavior and it doesn't help much.
* If there are unhandled items, the "push" function just blocks for a
few seconds and then re-queue them and retry.
* The new code doesn't do "worker booster"
* Gitea's queue's handlers are light functions, the cost is only the
go-routine, so it doesn't make sense to "boost" them.
* The new code only use "max worker number" to limit the concurrent
workers.
* The new "Push" never blocks forever
* Instead of creating more and more blocking goroutines, return an error
is more friendly to the server and to the end user.

There are more details in code comments: eg: the "Flush" problem, the
strange "code.index" hanging problem, the "immediate" queue problem.

Almost ready for review.

TODO:

* [x] add some necessary comments during review
* [x] add some more tests if necessary
* [x] update documents and config options
* [x] test max worker / active worker
* [x] re-run the CI tasks to see whether any test is flaky
* [x] improve the `handleOldLengthConfiguration` to provide more
friendly messages
* [x] fine tune default config values (eg: length?)

## Code coverage:

![image](https://user-images.githubusercontent.com/2114189/236620635-55576955-f95d-4810-b12f-879026a3afdf.png)

14 files changed, 67 insertions, 94 deletions

diff --git a/services/actions/init.go b/services/actions/init.go
index 3fd03eeb6f..8a9a30084a 100644
--- a/services/actions/init.go
+++ b/services/actions/init.go
@@ -15,7 +15,7 @@ func Init() {
 		return
 	}
 
-	jobEmitterQueue = queue.CreateUniqueQueue("actions_ready_job", jobEmitterQueueHandle, new(jobUpdate))
+	jobEmitterQueue = queue.CreateUniqueQueue("actions_ready_job", jobEmitterQueueHandler)
 	go graceful.GetManager().RunWithShutdownFns(jobEmitterQueue.Run)
 
 	notification.RegisterNotifier(NewNotifier())
diff --git a/services/actions/job_emitter.go b/services/actions/job_emitter.go
index c6b6fc551e..f7ec615364 100644
--- a/services/actions/job_emitter.go
+++ b/services/actions/job_emitter.go
@@ -16,7 +16,7 @@ import (
 	"xorm.io/builder"
 )
 
-var jobEmitterQueue queue.UniqueQueue
+var jobEmitterQueue *queue.WorkerPoolQueue[*jobUpdate]
 
 type jobUpdate struct {
 	RunID int64
@@ -32,13 +32,12 @@ func EmitJobsIfReady(runID int64) error {
 	return err
 }
 
-func jobEmitterQueueHandle(data ...queue.Data) []queue.Data {
+func jobEmitterQueueHandler(items ...*jobUpdate) []*jobUpdate {
 	ctx := graceful.GetManager().ShutdownContext()
-	var ret []queue.Data
-	for _, d := range data {
-		update := d.(*jobUpdate)
+	var ret []*jobUpdate
+	for _, update := range items {
 		if err := checkJobsOfRun(ctx, update.RunID); err != nil {
-			ret = append(ret, d)
+			ret = append(ret, update)
 		}
 	}
 	return ret
diff --git a/services/automerge/automerge.go b/services/automerge/automerge.go
index 9946047640..f001a6ccc5 100644
--- a/services/automerge/automerge.go
+++ b/services/automerge/automerge.go
@@ -25,11 +25,11 @@ import (
 )
 
 // prAutoMergeQueue represents a queue to handle update pull request tests
-var prAutoMergeQueue queue.UniqueQueue
+var prAutoMergeQueue *queue.WorkerPoolQueue[string]
 
 // Init runs the task queue to that handles auto merges
 func Init() error {
-	prAutoMergeQueue = queue.CreateUniqueQueue("pr_auto_merge", handle, "")
+	prAutoMergeQueue = queue.CreateUniqueQueue("pr_auto_merge", handler)
 	if prAutoMergeQueue == nil {
 		return fmt.Errorf("Unable to create pr_auto_merge Queue")
 	}
@@ -38,12 +38,12 @@ func Init() error {
 }
 
 // handle passed PR IDs and test the PRs
-func handle(data ...queue.Data) []queue.Data {
-	for _, d := range data {
+func handler(items ...string) []string {
+	for _, s := range items {
 		var id int64
 		var sha string
-		if _, err := fmt.Sscanf(d.(string), "%d_%s", &id, &sha); err != nil {
-			log.Error("could not parse data from pr_auto_merge queue (%v): %v", d, err)
+		if _, err := fmt.Sscanf(s, "%d_%s", &id, &sha); err != nil {
+			log.Error("could not parse data from pr_auto_merge queue (%v): %v", s, err)
 			continue
 		}
 		handlePull(id, sha)
@@ -52,10 +52,8 @@ func handle(data ...queue.Data) []queue.Data {
 }
 
 func addToQueue(pr *issues_model.PullRequest, sha string) {
-	if err := prAutoMergeQueue.PushFunc(fmt.Sprintf("%d_%s", pr.ID, sha), func() error {
-		log.Trace("Adding pullID: %d to the pull requests patch checking queue with sha %s", pr.ID, sha)
-		return nil
-	}); err != nil {
+	log.Trace("Adding pullID: %d to the pull requests patch checking queue with sha %s", pr.ID, sha)
+	if err := prAutoMergeQueue.Push(fmt.Sprintf("%d_%s", pr.ID, sha)); err != nil {
 		log.Error("Error adding pullID: %d to the pull requests patch checking queue %v", pr.ID, err)
 	}
 }
diff --git a/services/convert/utils_test.go b/services/convert/utils_test.go
index d1ec5980ce..1ac03a3097 100644
--- a/services/convert/utils_test.go
+++ b/services/convert/utils_test.go
@@ -7,8 +7,6 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-
-	_ "github.com/mattn/go-sqlite3"
 )
 
 func TestToCorrectPageSize(t *testing.T) {
diff --git a/services/mailer/mailer.go b/services/mailer/mailer.go
index 3d878b7c8c..5aeda9ed79 100644
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@@ -378,7 +378,7 @@ func (s *dummySender) Send(from string, to []string, msg io.WriterTo) error {
 	return nil
 }
 
-var mailQueue queue.Queue
+var mailQueue *queue.WorkerPoolQueue[*Message]
 
 // Sender sender for sending mail synchronously
 var Sender gomail.Sender
@@ -401,9 +401,8 @@ func NewContext(ctx context.Context) {
 		Sender = &smtpSender{}
 	}
 
-	mailQueue = queue.CreateQueue("mail", func(data ...queue.Data) []queue.Data {
-		for _, datum := range data {
-			msg := datum.(*Message)
+	mailQueue = queue.CreateSimpleQueue("mail", func(items ...*Message) []*Message {
+		for _, msg := range items {
 			gomailMsg := msg.ToMessage()
 			log.Trace("New e-mail sending request %s: %s", gomailMsg.GetHeader("To"), msg.Info)
 			if err := gomail.Send(Sender, gomailMsg); err != nil {
@@ -413,7 +412,7 @@ func NewContext(ctx context.Context) {
 			}
 		}
 		return nil
-	}, &Message{})
+	})
 
 	go graceful.GetManager().RunWithShutdownFns(mailQueue.Run)
 
diff --git a/services/migrations/github.go b/services/migrations/github.go
index 26e8813536..3e63fddb6a 100644
--- a/services/migrations/github.go
+++ b/services/migrations/github.go
@@ -19,7 +19,6 @@ import (
 	base "code.gitea.io/gitea/modules/migration"
 	"code.gitea.io/gitea/modules/proxy"
 	"code.gitea.io/gitea/modules/structs"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/google/go-github/v51/github"
 	"golang.org/x/oauth2"
@@ -164,7 +163,7 @@ func (g *GithubDownloaderV3) waitAndPickClient() {
 		timer := time.NewTimer(time.Until(g.rates[g.curClientIdx].Reset.Time))
 		select {
 		case <-g.ctx.Done():
-			util.StopTimer(timer)
+			timer.Stop()
 			return
 		case <-timer.C:
 		}
diff --git a/services/mirror/mirror.go b/services/mirror/mirror.go
index 9e569a70e3..35ba09521b 100644
--- a/services/mirror/mirror.go
+++ b/services/mirror/mirror.go
@@ -120,9 +120,8 @@ func Update(ctx context.Context, pullLimit, pushLimit int) error {
 	return nil
 }
 
-func queueHandle(data ...queue.Data) []queue.Data {
-	for _, datum := range data {
-		req := datum.(*mirror_module.SyncRequest)
+func queueHandler(items ...*mirror_module.SyncRequest) []*mirror_module.SyncRequest {
+	for _, req := range items {
 		doMirrorSync(graceful.GetManager().ShutdownContext(), req)
 	}
 	return nil
@@ -130,5 +129,5 @@ func queueHandle(data ...queue.Data) []queue.Data {
 
 // InitSyncMirrors initializes a go routine to sync the mirrors
 func InitSyncMirrors() {
-	mirror_module.StartSyncMirrors(queueHandle)
+	mirror_module.StartSyncMirrors(queueHandler)
 }
diff --git a/services/pull/check.go b/services/pull/check.go
index 02d9015414..8bc2bdff1d 100644
--- a/services/pull/check.go
+++ b/services/pull/check.go
@@ -30,7 +30,7 @@ import (
 )
 
 // prPatchCheckerQueue represents a queue to handle update pull request tests
-var prPatchCheckerQueue queue.UniqueQueue
+var prPatchCheckerQueue *queue.WorkerPoolQueue[string]
 
 var (
 	ErrIsClosed              = errors.New("pull is closed")
@@ -44,16 +44,14 @@ var (
 
 // AddToTaskQueue adds itself to pull request test task queue.
 func AddToTaskQueue(pr *issues_model.PullRequest) {
-	err := prPatchCheckerQueue.PushFunc(strconv.FormatInt(pr.ID, 10), func() error {
-		pr.Status = issues_model.PullRequestStatusChecking
-		err := pr.UpdateColsIfNotMerged(db.DefaultContext, "status")
-		if err != nil {
-			log.Error("AddToTaskQueue(%-v).UpdateCols.(add to queue): %v", pr, err)
-		} else {
-			log.Trace("Adding %-v to the test pull requests queue", pr)
-		}
-		return err
-	})
+	pr.Status = issues_model.PullRequestStatusChecking
+	err := pr.UpdateColsIfNotMerged(db.DefaultContext, "status")
+	if err != nil {
+		log.Error("AddToTaskQueue(%-v).UpdateCols.(add to queue): %v", pr, err)
+		return
+	}
+	log.Trace("Adding %-v to the test pull requests queue", pr)
+	err = prPatchCheckerQueue.Push(strconv.FormatInt(pr.ID, 10))
 	if err != nil && err != queue.ErrAlreadyInQueue {
 		log.Error("Error adding %-v to the test pull requests queue: %v", pr, err)
 	}
@@ -315,10 +313,8 @@ func InitializePullRequests(ctx context.Context) {
 		case <-ctx.Done():
 			return
 		default:
-			if err := prPatchCheckerQueue.PushFunc(strconv.FormatInt(prID, 10), func() error {
-				log.Trace("Adding PR[%d] to the pull requests patch checking queue", prID)
-				return nil
-			}); err != nil {
+			log.Trace("Adding PR[%d] to the pull requests patch checking queue", prID)
+			if err := prPatchCheckerQueue.Push(strconv.FormatInt(prID, 10)); err != nil {
 				log.Error("Error adding PR[%d] to the pull requests patch checking queue %v", prID, err)
 			}
 		}
@@ -326,10 +322,9 @@ func InitializePullRequests(ctx context.Context) {
 }
 
 // handle passed PR IDs and test the PRs
-func handle(data ...queue.Data) []queue.Data {
-	for _, datum := range data {
-		id, _ := strconv.ParseInt(datum.(string), 10, 64)
-
+func handler(items ...string) []string {
+	for _, s := range items {
+		id, _ := strconv.ParseInt(s, 10, 64)
 		testPR(id)
 	}
 	return nil
@@ -389,7 +384,7 @@ func CheckPRsForBaseBranch(baseRepo *repo_model.Repository, baseBranchName strin
 
 // Init runs the task queue to test all the checking status pull requests
 func Init() error {
-	prPatchCheckerQueue = queue.CreateUniqueQueue("pr_patch_checker", handle, "")
+	prPatchCheckerQueue = queue.CreateUniqueQueue("pr_patch_checker", handler)
 
 	if prPatchCheckerQueue == nil {
 		return fmt.Errorf("Unable to create pr_patch_checker Queue")
diff --git a/services/pull/check_test.go b/services/pull/check_test.go
index 590065250f..52209b4d35 100644
--- a/services/pull/check_test.go
+++ b/services/pull/check_test.go
@@ -12,6 +12,7 @@ import (
 	issues_model "code.gitea.io/gitea/models/issues"
 	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/modules/queue"
+	"code.gitea.io/gitea/modules/setting"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -20,27 +21,18 @@ func TestPullRequest_AddToTaskQueue(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
 
 	idChan := make(chan int64, 10)
-
-	q, err := queue.NewChannelUniqueQueue(func(data ...queue.Data) []queue.Data {
-		for _, datum := range data {
-			id, _ := strconv.ParseInt(datum.(string), 10, 64)
+	testHandler := func(items ...string) []string {
+		for _, s := range items {
+			id, _ := strconv.ParseInt(s, 10, 64)
 			idChan <- id
 		}
 		return nil
-	}, queue.ChannelUniqueQueueConfiguration{
-		WorkerPoolConfiguration: queue.WorkerPoolConfiguration{
-			QueueLength: 10,
-			BatchLength: 1,
-			Name:        "temporary-queue",
-		},
-		Workers: 1,
-	}, "")
-	assert.NoError(t, err)
-
-	queueShutdown := []func(){}
-	queueTerminate := []func(){}
+	}
 
-	prPatchCheckerQueue = q.(queue.UniqueQueue)
+	cfg, err := setting.GetQueueSettings(setting.CfgProvider, "pr_patch_checker")
+	assert.NoError(t, err)
+	prPatchCheckerQueue, err = queue.NewWorkerPoolQueueBySetting("pr_patch_checker", cfg, testHandler, true)
+	assert.NoError(t, err)
 
 	pr := unittest.AssertExistsAndLoadBean(t, &issues_model.PullRequest{ID: 2})
 	AddToTaskQueue(pr)
@@ -54,7 +46,8 @@ func TestPullRequest_AddToTaskQueue(t *testing.T) {
 	assert.True(t, has)
 	assert.NoError(t, err)
 
-	prPatchCheckerQueue.Run(func(shutdown func()) {
+	var queueShutdown, queueTerminate []func()
+	go prPatchCheckerQueue.Run(func(shutdown func()) {
 		queueShutdown = append(queueShutdown, shutdown)
 	}, func(terminate func()) {
 		queueTerminate = append(queueTerminate, terminate)
diff --git a/services/repository/archiver/archiver.go b/services/repository/archiver/archiver.go
index 1da4425cfc..1c514a4112 100644
--- a/services/repository/archiver/archiver.go
+++ b/services/repository/archiver/archiver.go
@@ -295,26 +295,21 @@ func ArchiveRepository(request *ArchiveRequest) (*repo_model.RepoArchiver, error
 	return doArchive(request)
 }
 
-var archiverQueue queue.UniqueQueue
+var archiverQueue *queue.WorkerPoolQueue[*ArchiveRequest]
 
 // Init initlize archive
 func Init() error {
-	handler := func(data ...queue.Data) []queue.Data {
-		for _, datum := range data {
-			archiveReq, ok := datum.(*ArchiveRequest)
-			if !ok {
-				log.Error("Unable to process provided datum: %v - not possible to cast to IndexerData", datum)
-				continue
-			}
+	handler := func(items ...*ArchiveRequest) []*ArchiveRequest {
+		for _, archiveReq := range items {
 			log.Trace("ArchiverData Process: %#v", archiveReq)
 			if _, err := doArchive(archiveReq); err != nil {
-				log.Error("Archive %v failed: %v", datum, err)
+				log.Error("Archive %v failed: %v", archiveReq, err)
 			}
 		}
 		return nil
 	}
 
-	archiverQueue = queue.CreateUniqueQueue("repo-archive", handler, new(ArchiveRequest))
+	archiverQueue = queue.CreateUniqueQueue("repo-archive", handler)
 	if archiverQueue == nil {
 		return errors.New("unable to create codes indexer queue")
 	}
diff --git a/services/repository/push.go b/services/repository/push.go
index 7f174c71b3..c7ea8f336e 100644
--- a/services/repository/push.go
+++ b/services/repository/push.go
@@ -29,12 +29,11 @@ import (
 )
 
 // pushQueue represents a queue to handle update pull request tests
-var pushQueue queue.Queue
+var pushQueue *queue.WorkerPoolQueue[[]*repo_module.PushUpdateOptions]
 
 // handle passed PR IDs and test the PRs
-func handle(data ...queue.Data) []queue.Data {
-	for _, datum := range data {
-		opts := datum.([]*repo_module.PushUpdateOptions)
+func handler(items ...[]*repo_module.PushUpdateOptions) [][]*repo_module.PushUpdateOptions {
+	for _, opts := range items {
 		if err := pushUpdates(opts); err != nil {
 			log.Error("pushUpdate failed: %v", err)
 		}
@@ -43,7 +42,7 @@ func handle(data ...queue.Data) []queue.Data {
 }
 
 func initPushQueue() error {
-	pushQueue = queue.CreateQueue("push_update", handle, []*repo_module.PushUpdateOptions{})
+	pushQueue = queue.CreateSimpleQueue("push_update", handler)
 	if pushQueue == nil {
 		return errors.New("unable to create push_update Queue")
 	}
diff --git a/services/task/task.go b/services/task/task.go
index 41bc07f2f6..4f1ba3a60b 100644
--- a/services/task/task.go
+++ b/services/task/task.go
@@ -23,7 +23,7 @@ import (
 )
 
 // taskQueue is a global queue of tasks
-var taskQueue queue.Queue
+var taskQueue *queue.WorkerPoolQueue[*admin_model.Task]
 
 // Run a task
 func Run(t *admin_model.Task) error {
@@ -37,7 +37,7 @@ func Run(t *admin_model.Task) error {
 
 // Init will start the service to get all unfinished tasks and run them
 func Init() error {
-	taskQueue = queue.CreateQueue("task", handle, &admin_model.Task{})
+	taskQueue = queue.CreateSimpleQueue("task", handler)
 
 	if taskQueue == nil {
 		return fmt.Errorf("Unable to create Task Queue")
@@ -48,9 +48,8 @@ func Init() error {
 	return nil
 }
 
-func handle(data ...queue.Data) []queue.Data {
-	for _, datum := range data {
-		task := datum.(*admin_model.Task)
+func handler(items ...*admin_model.Task) []*admin_model.Task {
+	for _, task := range items {
 		if err := Run(task); err != nil {
 			log.Error("Run task failed: %v", err)
 		}
diff --git a/services/webhook/deliver.go b/services/webhook/deliver.go
index 31246c1555..e817783e55 100644
--- a/services/webhook/deliver.go
+++ b/services/webhook/deliver.go
@@ -283,7 +283,7 @@ func Init() error {
 		},
 	}
 
-	hookQueue = queue.CreateUniqueQueue("webhook_sender", handle, int64(0))
+	hookQueue = queue.CreateUniqueQueue("webhook_sender", handler)
 	if hookQueue == nil {
 		return fmt.Errorf("Unable to create webhook_sender Queue")
 	}
diff --git a/services/webhook/webhook.go b/services/webhook/webhook.go
index b862d5bff1..3cd9deafd8 100644
--- a/services/webhook/webhook.go
+++ b/services/webhook/webhook.go
@@ -77,7 +77,7 @@ func IsValidHookTaskType(name string) bool {
 }
 
 // hookQueue is a global queue of web hooks
-var hookQueue queue.UniqueQueue
+var hookQueue *queue.WorkerPoolQueue[int64]
 
 // getPayloadBranch returns branch for hook event, if applicable.
 func getPayloadBranch(p api.Payloader) string {
@@ -105,13 +105,13 @@ type EventSource struct {
 }
 
 // handle delivers hook tasks
-func handle(data ...queue.Data) []queue.Data {
+func handler(items ...int64) []int64 {
 	ctx := graceful.GetManager().HammerContext()
 
-	for _, taskID := range data {
-		task, err := webhook_model.GetHookTaskByID(ctx, taskID.(int64))
+	for _, taskID := range items {
+		task, err := webhook_model.GetHookTaskByID(ctx, taskID)
 		if err != nil {
-			log.Error("GetHookTaskByID[%d] failed: %v", taskID.(int64), err)
+			log.Error("GetHookTaskByID[%d] failed: %v", taskID, err)
 			continue
 		}