PLT-6080 moving clustering to memberlist (#6499)

* PLT-6080 adding cluster discovery service

* Adding memberlist lib

* Adding memberlist lib

* WIP

* WIP

* WIP

* WIP

* Rolling back config changes

* Fixing make file

* Fixing config for cluster

* WIP

* Fixing system console for clustering

* Fixing default config

* Fixing config

* Fixing system console for clustering

* Tweaking hub setting

* Bumping up time

* merging vendor dir

* Updating vendor dir

* Fixing unit test

* Fixing bad merge

* Remove some testing code

* Moving comment

* PLT-6868 adding db ping retry

* Removing unused loc strings

* Adding defer to cancel

app/cluster_discovery.go

@@ -0,0 +1,77 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"fmt"
+	"time"
+
+	l4g "github.com/alecthomas/log4go"
+	"github.com/mattermost/platform/model"
+)
+
+const (
+	DISCOVERY_SERVICE_WRITE_PING = 60 * time.Second
+)
+
+type ClusterDiscoveryService struct {
+	model.ClusterDiscovery
+	stop chan bool
+}
+
+func NewClusterDiscoveryService() *ClusterDiscoveryService {
+	ds := &ClusterDiscoveryService{
+		ClusterDiscovery: model.ClusterDiscovery{},
+		stop:             make(chan bool),
+	}
+
+	return ds
+}
+
+func (me *ClusterDiscoveryService) Start() {
+
+	<-Srv.Store.ClusterDiscovery().Cleanup()
+
+	if cresult := <-Srv.Store.ClusterDiscovery().Exists(&me.ClusterDiscovery); cresult.Err != nil {
+		l4g.Error(fmt.Sprintf("ClusterDiscoveryService failed to check if row exists for %v with err=%v", me.ClusterDiscovery.ToJson(), cresult.Err))
+	} else {
+		if cresult.Data.(bool) {
+			if u := <-Srv.Store.ClusterDiscovery().Delete(&me.ClusterDiscovery); u.Err != nil {
+				l4g.Error(fmt.Sprintf("ClusterDiscoveryService failed to start clean for %v with err=%v", me.ClusterDiscovery.ToJson(), u.Err))
+			}
+		}
+	}
+
+	if result := <-Srv.Store.ClusterDiscovery().Save(&me.ClusterDiscovery); result.Err != nil {
+		l4g.Error(fmt.Sprintf("ClusterDiscoveryService failed to save for %v with err=%v", me.ClusterDiscovery.ToJson(), result.Err))
+		return
+	}
+
+	go func() {
+		l4g.Debug(fmt.Sprintf("ClusterDiscoveryService ping writer started for %v", me.ClusterDiscovery.ToJson()))
+		ticker := time.NewTicker(DISCOVERY_SERVICE_WRITE_PING)
+		defer func() {
+			ticker.Stop()
+			if u := <-Srv.Store.ClusterDiscovery().Delete(&me.ClusterDiscovery); u.Err != nil {
+				l4g.Error(fmt.Sprintf("ClusterDiscoveryService failed to cleanup for %v with err=%v", me.ClusterDiscovery.ToJson(), u.Err))
+			}
+			l4g.Debug(fmt.Sprintf("ClusterDiscoveryService ping writer stopped for %v", me.ClusterDiscovery.ToJson()))
+		}()
+
+		for {
+			select {
+			case <-ticker.C:
+				if u := <-Srv.Store.ClusterDiscovery().SetLastPingAt(&me.ClusterDiscovery); u.Err != nil {
+					l4g.Error(fmt.Sprintf("ClusterDiscoveryService failed to write ping for %v with err=%v", me.ClusterDiscovery.ToJson(), u.Err))
+				}
+			case <-me.stop:
+				return
+			}
+		}
+	}()
+}
+
+func (me *ClusterDiscoveryService) Stop() {
+	me.stop <- true
+}