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)

1 files changed, 212 insertions, 0 deletions

diff --git a/modules/testlogger/testlogger.go b/modules/testlogger/testlogger.go
new file mode 100644
index 0000000000..bf912f41dc
--- /dev/null
+++ b/modules/testlogger/testlogger.go
@@ -0,0 +1,212 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package testlogger
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/queue"
+)
+
+var (
+	prefix    string
+	SlowTest  = 10 * time.Second
+	SlowFlush = 5 * time.Second
+)
+
+// TestLogger is a logger which will write to the testing log
+type TestLogger struct {
+	log.WriterLogger
+}
+
+var WriterCloser = &testLoggerWriterCloser{}
+
+type testLoggerWriterCloser struct {
+	sync.RWMutex
+	t []*testing.TB
+}
+
+func (w *testLoggerWriterCloser) pushT(t *testing.TB) {
+	w.Lock()
+	w.t = append(w.t, t)
+	w.Unlock()
+}
+
+func (w *testLoggerWriterCloser) Write(p []byte) (int, error) {
+	// There was a data race problem: the logger system could still try to output logs after the runner is finished.
+	// So we must ensure that the "t" in stack is still valid.
+	w.RLock()
+	defer w.RUnlock()
+
+	var t *testing.TB
+	if len(w.t) > 0 {
+		t = w.t[len(w.t)-1]
+	}
+
+	if len(p) > 0 && p[len(p)-1] == '\n' {
+		p = p[:len(p)-1]
+	}
+
+	if t == nil || *t == nil {
+		return fmt.Fprintf(os.Stdout, "??? [Unknown Test] %s\n", p)
+	}
+
+	defer func() {
+		err := recover()
+		if err == nil {
+			return
+		}
+		var errString string
+		errErr, ok := err.(error)
+		if ok {
+			errString = errErr.Error()
+		} else {
+			errString, ok = err.(string)
+		}
+		if !ok {
+			panic(err)
+		}
+		if !strings.HasPrefix(errString, "Log in goroutine after ") {
+			panic(err)
+		}
+	}()
+
+	(*t).Log(string(p))
+	return len(p), nil
+}
+
+func (w *testLoggerWriterCloser) popT() {
+	w.Lock()
+	if len(w.t) > 0 {
+		w.t = w.t[:len(w.t)-1]
+	}
+	w.Unlock()
+}
+
+func (w *testLoggerWriterCloser) Close() error {
+	return nil
+}
+
+func (w *testLoggerWriterCloser) Reset() {
+	w.Lock()
+	if len(w.t) > 0 {
+		for _, t := range w.t {
+			if t == nil {
+				continue
+			}
+			fmt.Fprintf(os.Stdout, "Unclosed logger writer in test: %s", (*t).Name())
+			(*t).Errorf("Unclosed logger writer in test: %s", (*t).Name())
+		}
+		w.t = nil
+	}
+	w.Unlock()
+}
+
+// PrintCurrentTest prints the current test to os.Stdout
+func PrintCurrentTest(t testing.TB, skip ...int) func() {
+	start := time.Now()
+	actualSkip := 1
+	if len(skip) > 0 {
+		actualSkip = skip[0]
+	}
+	_, filename, line, _ := runtime.Caller(actualSkip)
+
+	if log.CanColorStdout {
+		fmt.Fprintf(os.Stdout, "=== %s (%s:%d)\n", fmt.Formatter(log.NewColoredValue(t.Name())), strings.TrimPrefix(filename, prefix), line)
+	} else {
+		fmt.Fprintf(os.Stdout, "=== %s (%s:%d)\n", t.Name(), strings.TrimPrefix(filename, prefix), line)
+	}
+	WriterCloser.pushT(&t)
+	return func() {
+		took := time.Since(start)
+		if took > SlowTest {
+			if log.CanColorStdout {
+				fmt.Fprintf(os.Stdout, "+++ %s is a slow test (took %v)\n", fmt.Formatter(log.NewColoredValue(t.Name(), log.Bold, log.FgYellow)), fmt.Formatter(log.NewColoredValue(took, log.Bold, log.FgYellow)))
+			} else {
+				fmt.Fprintf(os.Stdout, "+++ %s is a slow test (took %v)\n", t.Name(), took)
+			}
+		}
+		timer := time.AfterFunc(SlowFlush, func() {
+			if log.CanColorStdout {
+				fmt.Fprintf(os.Stdout, "+++ %s ... still flushing after %v ...\n", fmt.Formatter(log.NewColoredValue(t.Name(), log.Bold, log.FgRed)), SlowFlush)
+			} else {
+				fmt.Fprintf(os.Stdout, "+++ %s ... still flushing after %v ...\n", t.Name(), SlowFlush)
+			}
+		})
+		if err := queue.GetManager().FlushAll(context.Background(), time.Minute); err != nil {
+			t.Errorf("Flushing queues failed with error %v", err)
+		}
+		timer.Stop()
+		flushTook := time.Since(start) - took
+		if flushTook > SlowFlush {
+			if log.CanColorStdout {
+				fmt.Fprintf(os.Stdout, "+++ %s had a slow clean-up flush (took %v)\n", fmt.Formatter(log.NewColoredValue(t.Name(), log.Bold, log.FgRed)), fmt.Formatter(log.NewColoredValue(flushTook, log.Bold, log.FgRed)))
+			} else {
+				fmt.Fprintf(os.Stdout, "+++ %s had a slow clean-up flush (took %v)\n", t.Name(), flushTook)
+			}
+		}
+		WriterCloser.popT()
+	}
+}
+
+// Printf takes a format and args and prints the string to os.Stdout
+func Printf(format string, args ...interface{}) {
+	if log.CanColorStdout {
+		for i := 0; i < len(args); i++ {
+			args[i] = log.NewColoredValue(args[i])
+		}
+	}
+	fmt.Fprintf(os.Stdout, "\t"+format, args...)
+}
+
+// NewTestLogger creates a TestLogger as a log.LoggerProvider
+func NewTestLogger() log.LoggerProvider {
+	logger := &TestLogger{}
+	logger.Colorize = log.CanColorStdout
+	logger.Level = log.TRACE
+	return logger
+}
+
+// Init inits connection writer with json config.
+// json config only need key "level".
+func (log *TestLogger) Init(config string) error {
+	err := json.Unmarshal([]byte(config), log)
+	if err != nil {
+		return err
+	}
+	log.NewWriterLogger(WriterCloser)
+	return nil
+}
+
+// Flush when log should be flushed
+func (log *TestLogger) Flush() {
+}
+
+// ReleaseReopen does nothing
+func (log *TestLogger) ReleaseReopen() error {
+	return nil
+}
+
+// GetName returns the default name for this implementation
+func (log *TestLogger) GetName() string {
+	return "test"
+}
+
+func init() {
+	const relFilePath = "modules/testlogger/testlogger.go"
+	_, filename, _, _ := runtime.Caller(0)
+	if !strings.HasSuffix(filename, relFilePath) {
+		panic("source code file path doesn't match expected: " + relFilePath)
+	}
+	prefix = strings.TrimSuffix(filename, relFilePath)
+}