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)

3 files changed, 76 insertions, 220 deletions

diff --git a/templates/admin/monitor.tmpl b/templates/admin/monitor.tmpl
index 1ab6b75a1e..6a13b7b552 100644
--- a/templates/admin/monitor.tmpl
+++ b/templates/admin/monitor.tmpl
@@ -1,36 +1,7 @@
 {{template "admin/layout_head" (dict "ctxData" . "pageClass" "admin monitor")}}
 	<div class="admin-setting-content">
 		{{template "admin/cron" .}}
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queues"}}
-		</h4>
-		<div class="ui attached table segment">
-			<table class="ui very basic striped table unstackable">
-				<thead>
-					<tr>
-						<th>{{.locale.Tr "admin.monitor.queue.name"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.type"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.exemplar"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.numberinqueue"}}</th>
-						<th></th>
-					</tr>
-				</thead>
-				<tbody>
-					{{range .Queues}}
-						<tr>
-							<td>{{.Name}}</td>
-							<td>{{.Type}}</td>
-							<td>{{.ExemplarType}}</td>
-							<td>{{$sum := .NumberOfWorkers}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
-							<td>{{$sum = .NumberInQueue}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
-							<td><a href="{{$.Link}}/queue/{{.QID}}" class="button">{{if lt $sum 0}}{{$.locale.Tr "admin.monitor.queue.review"}}{{else}}{{$.locale.Tr "admin.monitor.queue.review_add"}}{{end}}</a>
-						</tr>
-					{{end}}
-				</tbody>
-			</table>
-		</div>
-
+		{{template "admin/queue" .}}
 		{{template "admin/process" .}}
 	</div>
 
diff --git a/templates/admin/queue.tmpl b/templates/admin/queue.tmpl
index 84eb8892ef..5bd507e69f 100644
--- a/templates/admin/queue.tmpl
+++ b/templates/admin/queue.tmpl
@@ -1,192 +1,29 @@
-{{template "admin/layout_head" (dict "ctxData" . "pageClass" "admin monitor")}}
-	<div class="admin-setting-content">
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue" .Queue.Name}}
-		</h4>
-		<div class="ui attached table segment">
-			<table class="ui very basic striped table">
-				<thead>
-					<tr>
-						<th>{{.locale.Tr "admin.monitor.queue.name"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.type"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.exemplar"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.maxnumberworkers"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.numberinqueue"}}</th>
-					</tr>
-				</thead>
-				<tbody>
-					<tr>
-						<td>{{.Queue.Name}}</td>
-						<td>{{.Queue.Type}}</td>
-						<td>{{.Queue.ExemplarType}}</td>
-						<td>{{$sum := .Queue.NumberOfWorkers}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
-						<td>{{if lt $sum 0}}-{{else}}{{.Queue.MaxNumberOfWorkers}}{{end}}</td>
-						<td>{{$sum = .Queue.NumberInQueue}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
-					</tr>
-				</tbody>
-			</table>
-		</div>
-		{{if lt $sum 0}}
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.nopool.title"}}
-		</h4>
-		<div class="ui attached segment">
-			{{if eq .Queue.Type "wrapped"}}
-			<p>{{.locale.Tr "admin.monitor.queue.wrapped.desc"}}</p>
-			{{else if eq .Queue.Type "persistable-channel"}}
-			<p>{{.locale.Tr "admin.monitor.queue.persistable-channel.desc"}}</p>
-			{{else}}
-			<p>{{.locale.Tr "admin.monitor.queue.nopool.desc"}}</p>
-			{{end}}
-		</div>
-		{{else}}
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.settings.title"}}
-		</h4>
-		<div class="ui attached segment">
-			<p>{{.locale.Tr "admin.monitor.queue.settings.desc"}}</p>
-			<form method="POST" action="{{.Link}}/set">
-				{{$.CsrfTokenHtml}}
-				<div class="ui form">
-					<div class="inline field">
-						<label for="max-number">{{.locale.Tr "admin.monitor.queue.settings.maxnumberworkers"}}</label>
-						<input name="max-number" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.settings.maxnumberworkers.placeholder" .Queue.MaxNumberOfWorkers}}">
-					</div>
-					<div class="inline field">
-						<label for="timeout">{{.locale.Tr "admin.monitor.queue.settings.timeout"}}</label>
-						<input name="timeout" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.settings.timeout.placeholder" .Queue.BoostTimeout}}">
-					</div>
-					<div class="inline field">
-						<label for="number">{{.locale.Tr "admin.monitor.queue.settings.numberworkers"}}</label>
-						<input name="number" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.settings.numberworkers.placeholder" .Queue.BoostWorkers}}">
-					</div>
-					<div class="inline field">
-						<label>{{.locale.Tr "admin.monitor.queue.settings.blocktimeout"}}</label>
-						<span>{{.locale.Tr "admin.monitor.queue.settings.blocktimeout.value" .Queue.BlockTimeout}}</span>
-					</div>
-					<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.settings.submit"}}</button>
-				</div>
-			</form>
-		</div>
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.pool.addworkers.title"}}
-		</h4>
-		<div class="ui attached segment">
-			<p>{{.locale.Tr "admin.monitor.queue.pool.addworkers.desc"}}</p>
-			<form method="POST" action="{{.Link}}/add">
-				{{$.CsrfTokenHtml}}
-				<div class="ui form">
-					<div class="fields">
-						<div class="field">
-							<label>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</label>
-							<input name="number" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.pool.addworkers.numberworkers.placeholder"}}">
-						</div>
-						<div class="field">
-							<label>{{.locale.Tr "admin.monitor.queue.pool.timeout"}}</label>
-							<input name="timeout" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.pool.addworkers.timeout.placeholder"}}">
-						</div>
-					</div>
-					<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.pool.addworkers.submit"}}</button>
-				</div>
-			</form>
-		</div>
-		{{if .Queue.Pausable}}
-			{{if .Queue.IsPaused}}
-				<h4 class="ui top attached header">
-					{{.locale.Tr "admin.monitor.queue.pool.resume.title"}}
-				</h4>
-				<div class="ui attached segment">
-					<p>{{.locale.Tr "admin.monitor.queue.pool.resume.desc"}}</p>
-					<form method="POST" action="{{.Link}}/resume">
-						{{$.CsrfTokenHtml}}
-						<div class="ui form">
-							<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.pool.resume.submit"}}</button>
-						</div>
-					</form>
-				</div>
-			{{else}}
-				<h4 class="ui top attached header">
-					{{.locale.Tr "admin.monitor.queue.pool.pause.title"}}
-				</h4>
-				<div class="ui attached segment">
-					<p>{{.locale.Tr "admin.monitor.queue.pool.pause.desc"}}</p>
-					<form method="POST" action="{{.Link}}/pause">
-						{{$.CsrfTokenHtml}}
-						<div class="ui form">
-							<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.pool.pause.submit"}}</button>
-						</div>
-					</form>
-				</div>
-			{{end}}
+<h4 class="ui top attached header">
+	{{.locale.Tr "admin.monitor.queues"}}
+</h4>
+<div class="ui attached table segment">
+	<table class="ui very basic striped table unstackable">
+		<thead>
+		<tr>
+			<th>{{.locale.Tr "admin.monitor.queue.name"}}</th>
+			<th>{{.locale.Tr "admin.monitor.queue.type"}}</th>
+			<th>{{.locale.Tr "admin.monitor.queue.exemplar"}}</th>
+			<th>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</th>
+			<th>{{.locale.Tr "admin.monitor.queue.numberinqueue"}}</th>
+			<th></th>
+		</tr>
+		</thead>
+		<tbody>
+		{{range $qid, $q := .Queues}}
+		<tr>
+			<td>{{$q.GetName}}</td>
+			<td>{{$q.GetType}}</td>
+			<td>{{$q.GetItemTypeName}}</td>
+			<td>{{$sum := $q.GetWorkerNumber}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
+			<td>{{$sum = $q.GetQueueItemNumber}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
+			<td><a href="{{$.Link}}/queue/{{$qid}}" class="button">{{if lt $sum 0}}{{$.locale.Tr "admin.monitor.queue.review"}}{{else}}{{$.locale.Tr "admin.monitor.queue.review_add"}}{{end}}</a>
+		</tr>
 		{{end}}
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.pool.flush.title"}}
-		</h4>
-		<div class="ui attached segment">
-			<p>{{.locale.Tr "admin.monitor.queue.pool.flush.desc"}}</p>
-			<form method="POST" action="{{.Link}}/flush">
-				{{$.CsrfTokenHtml}}
-				<div class="ui form">
-					<div class="fields">
-						<div class="field">
-							<label>{{.locale.Tr "admin.monitor.queue.pool.timeout"}}</label>
-							<input name="timeout" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.pool.addworkers.timeout.placeholder"}}">
-						</div>
-					</div>
-					<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.pool.flush.submit"}}</button>
-				</div>
-			</form>
-		</div>
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.pool.workers.title"}}
-		</h4>
-		<div class="ui attached table segment">
-			<table class="ui very basic striped table">
-				<thead>
-					<tr>
-						<th>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</th>
-						<th>{{.locale.Tr "admin.monitor.start"}}</th>
-						<th>{{.locale.Tr "admin.monitor.queue.pool.timeout"}}</th>
-						<th></th>
-					</tr>
-				</thead>
-				<tbody>
-					{{range .Queue.Workers}}
-					<tr>
-						<td>{{.Workers}}{{if .IsFlusher}}<span title="{{$.locale.Tr "admin.monitor.queue.flush"}}">{{svg "octicon-sync"}}</span>{{end}}</td>
-						<td>{{DateTime "full" .Start}}</td>
-						<td>{{if .HasTimeout}}{{DateTime "full" .Timeout}}{{else}}-{{end}}</td>
-						<td>
-							<a class="delete-button" href="" data-url="{{$.Link}}/cancel/{{.PID}}" data-id="{{.PID}}" data-name="{{.Workers}}" title="{{$.locale.Tr "remove"}}">{{svg "octicon-trash"}}</a>
-						</td>
-					</tr>
-					{{else}}
-						<tr>
-							<td colspan="4">{{.locale.Tr "admin.monitor.queue.pool.workers.none"}}
-						</tr>
-					{{end}}
-				</tbody>
-			</table>
-		</div>
-		{{end}}
-		<h4 class="ui top attached header">
-			{{.locale.Tr "admin.monitor.queue.configuration"}}
-		</h4>
-		<div class="ui attached segment">
-			<pre>{{JsonUtils.PrettyIndent .Queue.Configuration}}</pre>
-		</div>
-	</div>
-
-<div class="ui g-modal-confirm delete modal">
-	<div class="header">
-		{{.locale.Tr "admin.monitor.queue.pool.cancel"}}
-	</div>
-	<div class="content">
-		<p>{{$.locale.Tr "admin.monitor.queue.pool.cancel_notices" `<span class="name"></span>` | Safe}}</p>
-		<p>{{$.locale.Tr "admin.monitor.queue.pool.cancel_desc"}}</p>
-	</div>
-	{{template "base/modal_actions_confirm" .}}
+		</tbody>
+	</table>
 </div>
-
-{{template "admin/layout_footer" .}}
diff --git a/templates/admin/queue_manage.tmpl b/templates/admin/queue_manage.tmpl
new file mode 100644
index 0000000000..60d6b426b9
--- /dev/null
+++ b/templates/admin/queue_manage.tmpl
@@ -0,0 +1,48 @@
+{{template "admin/layout_head" (dict "ctxData" . "pageClass" "admin monitor")}}
+	<div class="admin-setting-content">
+		<h4 class="ui top attached header">
+			{{.locale.Tr "admin.monitor.queue" .Queue.GetName}}
+		</h4>
+		<div class="ui attached table segment">
+			<table class="ui very basic striped table">
+				<thead>
+					<tr>
+						<th>{{.locale.Tr "admin.monitor.queue.name"}}</th>
+						<th>{{.locale.Tr "admin.monitor.queue.type"}}</th>
+						<th>{{.locale.Tr "admin.monitor.queue.exemplar"}}</th>
+						<th>{{.locale.Tr "admin.monitor.queue.numberworkers"}}</th>
+						<th>{{.locale.Tr "admin.monitor.queue.maxnumberworkers"}}</th>
+						<th>{{.locale.Tr "admin.monitor.queue.numberinqueue"}}</th>
+					</tr>
+				</thead>
+				<tbody>
+					<tr>
+						<td>{{.Queue.GetName}}</td>
+						<td>{{.Queue.GetType}}</td>
+						<td>{{.Queue.GetItemTypeName}}</td>
+						<td>{{$sum := .Queue.GetWorkerNumber}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
+						<td>{{if lt $sum 0}}-{{else}}{{.Queue.GetWorkerMaxNumber}}{{end}}</td>
+						<td>{{$sum = .Queue.GetQueueItemNumber}}{{if lt $sum 0}}-{{else}}{{$sum}}{{end}}</td>
+					</tr>
+				</tbody>
+			</table>
+		</div>
+
+		<h4 class="ui top attached header">
+			{{.locale.Tr "admin.monitor.queue.settings.title"}}
+		</h4>
+		<div class="ui attached segment">
+			<p>{{.locale.Tr "admin.monitor.queue.settings.desc"}}</p>
+			<form method="POST" action="{{.Link}}/set">
+				{{$.CsrfTokenHtml}}
+				<div class="ui form">
+					<div class="inline field">
+						<label for="max-number">{{.locale.Tr "admin.monitor.queue.settings.maxnumberworkers"}}</label>
+						<input name="max-number" type="text" placeholder="{{.locale.Tr "admin.monitor.queue.settings.maxnumberworkers.placeholder" .Queue.GetWorkerMaxNumber}}">
+					</div>
+					<button class="ui submit button">{{.locale.Tr "admin.monitor.queue.settings.submit"}}</button>
+				</div>
+			</form>
+		</div>
+	</div>
+{{template "admin/layout_footer" .}}