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/app/platform/busy.go

@@ -0,0 +1,155 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package platform
+
+import (
+	"encoding/json"
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/server/channels/einterfaces"
+)
+
+const (
+	TimestampFormat = "Mon Jan 2 15:04:05 -0700 MST 2006"
+)
+
+// Busy represents the busy state of the server. A server marked busy
+// will have non-critical services disabled. If a Cluster is provided
+// any changes will be propagated to each node.
+type Busy struct {
+	busy    int32 // protected via atomic for fast IsBusy calls
+	mux     sync.RWMutex
+	timer   *time.Timer
+	expires time.Time
+
+	cluster einterfaces.ClusterInterface
+}
+
+// NewBusy creates a new Busy instance with optional cluster which will
+// be notified of busy state changes.
+func NewBusy(cluster einterfaces.ClusterInterface) *Busy {
+	return &Busy{cluster: cluster}
+}
+
+// IsBusy returns true if the server has been marked as busy.
+func (b *Busy) IsBusy() bool {
+	if b == nil {
+		return false
+	}
+	return atomic.LoadInt32(&b.busy) != 0
+}
+
+// Set marks the server as busy for dur duration and notifies cluster nodes.
+func (b *Busy) Set(dur time.Duration) {
+	b.mux.Lock()
+	defer b.mux.Unlock()
+
+	// minimum 1 second
+	if dur < (time.Second * 1) {
+		dur = time.Second * 1
+	}
+
+	b.setWithoutNotify(dur)
+
+	if b.cluster != nil {
+		sbs := &model.ServerBusyState{Busy: true, Expires: b.expires.Unix(), ExpiresTS: b.expires.UTC().Format(TimestampFormat)}
+		b.notifyServerBusyChange(sbs)
+	}
+}
+
+// must hold mutex
+func (b *Busy) setWithoutNotify(dur time.Duration) {
+	b.clearWithoutNotify()
+	atomic.StoreInt32(&b.busy, 1)
+	b.expires = time.Now().Add(dur)
+	b.timer = time.AfterFunc(dur, func() {
+		b.mux.Lock()
+		b.clearWithoutNotify()
+		b.mux.Unlock()
+	})
+}
+
+// ClearBusy marks the server as not busy and notifies cluster nodes.
+func (b *Busy) Clear() {
+	b.mux.Lock()
+	defer b.mux.Unlock()
+
+	b.clearWithoutNotify()
+
+	if b.cluster != nil {
+		sbs := &model.ServerBusyState{Busy: false, Expires: time.Time{}.Unix(), ExpiresTS: ""}
+		b.notifyServerBusyChange(sbs)
+	}
+}
+
+// must hold mutex
+func (b *Busy) clearWithoutNotify() {
+	if b.timer != nil {
+		b.timer.Stop() // don't drain timer.C channel for AfterFunc timers.
+	}
+	b.timer = nil
+	b.expires = time.Time{}
+	atomic.StoreInt32(&b.busy, 0)
+}
+
+// Expires returns the expected time that the server
+// will be marked not busy. This expiry can be extended
+// via additional calls to SetBusy.
+func (b *Busy) Expires() time.Time {
+	b.mux.RLock()
+	defer b.mux.RUnlock()
+	return b.expires
+}
+
+// notifyServerBusyChange informs all cluster members of a server busy state change.
+func (b *Busy) notifyServerBusyChange(sbs *model.ServerBusyState) {
+	if b.cluster == nil {
+		return
+	}
+	buf, _ := json.Marshal(sbs)
+	msg := &model.ClusterMessage{
+		Event:            model.ClusterEventBusyStateChanged,
+		SendType:         model.ClusterSendReliable,
+		WaitForAllToSend: true,
+		Data:             buf,
+	}
+	b.cluster.SendClusterMessage(msg)
+}
+
+// ClusterEventChanged is called when a CLUSTER_EVENT_BUSY_STATE_CHANGED is received.
+func (b *Busy) ClusterEventChanged(sbs *model.ServerBusyState) {
+	b.mux.Lock()
+	defer b.mux.Unlock()
+
+	if sbs.Busy {
+		expires := time.Unix(sbs.Expires, 0)
+		dur := time.Until(expires)
+		if dur > 0 {
+			b.setWithoutNotify(dur)
+		}
+	} else {
+		b.clearWithoutNotify()
+	}
+}
+
+func (b *Busy) ToJSON() ([]byte, error) {
+	b.mux.RLock()
+	defer b.mux.RUnlock()
+
+	sbs := &model.ServerBusyState{
+		Busy:      atomic.LoadInt32(&b.busy) != 0,
+		Expires:   b.expires.Unix(),
+		ExpiresTS: b.expires.UTC().Format(TimestampFormat),
+	}
+	sbsJSON, jsonErr := json.Marshal(sbs)
+	if jsonErr != nil {
+		return []byte{}, fmt.Errorf("failed to encode server busy state to JSON: %w", jsonErr)
+	}
+
+	return sbsJSON, nil
+}