Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/jobs/workers.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package jobs
+
+import (
+	"errors"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/server/platform/services/configservice"
+	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+)
+
+type Workers struct {
+	ConfigService configservice.ConfigService
+	Watcher       *Watcher
+
+	workers map[string]model.Worker
+
+	listenerId string
+	running    bool
+}
+
+var (
+	ErrWorkersNotRunning    = errors.New("job workers are not running")
+	ErrWorkersRunning       = errors.New("job workers are running")
+	ErrWorkersUninitialized = errors.New("job workers are not initialized")
+)
+
+func NewWorkers(configService configservice.ConfigService) *Workers {
+	return &Workers{
+		ConfigService: configService,
+		workers:       make(map[string]model.Worker),
+	}
+}
+
+func (workers *Workers) AddWorker(name string, worker model.Worker) {
+	workers.workers[name] = worker
+}
+
+func (workers *Workers) Get(name string) model.Worker {
+	return workers.workers[name]
+}
+
+// Start starts the workers. This call is not safe for concurrent use.
+// Synchronization should be implemented by the caller.
+func (workers *Workers) Start() {
+	mlog.Info("Starting workers")
+
+	for _, w := range workers.workers {
+		if w.IsEnabled(workers.ConfigService.Config()) {
+			go w.Run()
+		}
+	}
+
+	go workers.Watcher.Start()
+
+	workers.listenerId = workers.ConfigService.AddConfigListener(workers.handleConfigChange)
+	workers.running = true
+}
+
+func (workers *Workers) handleConfigChange(oldConfig *model.Config, newConfig *model.Config) {
+	mlog.Debug("Workers received config change.")
+
+	for _, w := range workers.workers {
+		if w.IsEnabled(oldConfig) && !w.IsEnabled(newConfig) {
+			w.Stop()
+		}
+		if !w.IsEnabled(oldConfig) && w.IsEnabled(newConfig) {
+			go w.Run()
+		}
+	}
+}
+
+// Stop stops the workers. This call is not safe for concurrent use.
+// Synchronization should be implemented by the caller.
+func (workers *Workers) Stop() {
+	workers.ConfigService.RemoveConfigListener(workers.listenerId)
+
+	workers.Watcher.Stop()
+
+	for _, w := range workers.workers {
+		if w.IsEnabled(workers.ConfigService.Config()) {
+			w.Stop()
+		}
+	}
+
+	workers.running = false
+
+	mlog.Info("Stopped workers")
+}