MM-11243: Make Elasticsearch work after enabling without restart. (#9146)

* MM-11243: Make Elasticsearch work after enabling without restart.

* Also cope with config vars changing whilst enabled.

app/app.go

@@ -680,3 +680,54 @@ func (a *App) DoEmojisPermissionsMigration() {
 		mlog.Critical(fmt.Sprint(result.Err))
 	}
 }
+
+func (a *App) StartElasticsearch() {
+	a.Go(func() {
+		if err := a.Elasticsearch.Start(); err != nil {
+			mlog.Error(err.Error())
+		}
+	})
+
+	a.AddConfigListener(func(oldConfig *model.Config, newConfig *model.Config) {
+		if *oldConfig.ElasticsearchSettings.EnableIndexing == false && *newConfig.ElasticsearchSettings.EnableIndexing == true {
+			a.Go(func() {
+				if err := a.Elasticsearch.Start(); err != nil {
+					mlog.Error(err.Error())
+				}
+			})
+		} else if *oldConfig.ElasticsearchSettings.EnableIndexing == true && *newConfig.ElasticsearchSettings.EnableIndexing == false {
+			a.Go(func() {
+				if err := a.Elasticsearch.Stop(); err != nil {
+					mlog.Error(err.Error())
+				}
+			})
+		} else if *oldConfig.ElasticsearchSettings.Password != *newConfig.ElasticsearchSettings.Password || *oldConfig.ElasticsearchSettings.Username != *newConfig.ElasticsearchSettings.Username || *oldConfig.ElasticsearchSettings.ConnectionUrl != *newConfig.ElasticsearchSettings.ConnectionUrl || *oldConfig.ElasticsearchSettings.Sniff != *newConfig.ElasticsearchSettings.Sniff {
+			a.Go(func() {
+				if *oldConfig.ElasticsearchSettings.EnableIndexing == true {
+					if err := a.Elasticsearch.Stop(); err != nil {
+						mlog.Error(err.Error())
+					}
+					if err := a.Elasticsearch.Start(); err != nil {
+						mlog.Error(err.Error())
+					}
+				}
+			})
+		}
+	})
+
+	a.AddLicenseListener(func() {
+		if a.License() != nil {
+			a.Go(func() {
+				if err := a.Elasticsearch.Start(); err != nil {
+					mlog.Error(err.Error())
+				}
+			})
+		} else {
+			a.Go(func() {
+				if err := a.Elasticsearch.Stop(); err != nil {
+					mlog.Error(err.Error())
+				}
+			})
+		}
+	})
+}

cmd/mattermost/commands/server.go

@@ -176,11 +176,7 @@ func runServer(configFileLocation string, disableConfigWatch bool, usedPlatform
 	}
 
 	if a.Elasticsearch != nil {
-		a.Go(func() {
+		a.StartElasticsearch()
-			if err := a.Elasticsearch.Start(); err != nil {
-				mlog.Error(err.Error())
-			}
-		})
 	}
 
 	if *a.Config().JobSettings.RunJobs {

einterfaces/elasticsearch.go

@@ -11,6 +11,7 @@ import (
 
 type ElasticsearchInterface interface {
 	Start() *model.AppError
+	Stop() *model.AppError
 	IndexPost(post *model.Post, teamId string) *model.AppError
 	SearchPosts(channels *model.ChannelList, searchParams []*model.SearchParams) ([]string, model.PostSearchMatches, *model.AppError)
 	DeletePost(post *model.Post) *model.AppError

i18n/en.json

@@ -167,6 +167,14 @@
     "id": "api.channel.join_channel.already_deleted.app_error",
     "translation": "Channel is already deleted"
   },
+  {
+    "id": "ent.elasticsearch.start.already_started.app_error",
+    "translation": "Elasticsearch is already started"
+  },
+  {
+    "id": "ent.elasticsearch.stop.already_stopped.app_error",
+    "translation": "Elasticsearch is already stopped"
+  },
   {
     "id": "api.channel.join_channel.permissions.app_error",
     "translation": "You do not have the appropriate permissions"