[GitHub] [incubator-yunikorn-k8shim] HuangTing-Yao commented on a change in pull request #219: [YUNIKORN-2] gang scheduling shim side implementation

[GitBox <gi...@apache.org>]

HuangTing-Yao commented on a change in pull request #219:
URL: https://github.com/apache/incubator-yunikorn-k8shim/pull/219#discussion_r558814340



##########
File path: pkg/cache/placeholder_manager.go
##########
@@ -0,0 +1,167 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package cache
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"go.uber.org/zap"
+	v1 "k8s.io/api/core/v1"
+
+	"github.com/apache/incubator-yunikorn-k8shim/pkg/client"
+	"github.com/apache/incubator-yunikorn-k8shim/pkg/common/utils"
+	"github.com/apache/incubator-yunikorn-k8shim/pkg/log"
+)
+
+// placeholder manager is a service to manage the lifecycle of app placeholders
+type PlaceholderManager struct {
+	clients   *client.Clients
+	orphanPod map[string]*v1.Pod
+	stopChan  chan struct{}
+	running   atomic.Value
+	sync.RWMutex
+}
+
+var placeholderMgr *PlaceholderManager
+var once sync.Once
+
+func NewPlaceholderManager(clients *client.Clients) *PlaceholderManager {
+	var r atomic.Value
+	r.Store(false)
+	placeholderMgr = &PlaceholderManager{
+		clients: clients,
+		running: r,
+	}
+	return placeholderMgr
+}
+
+func GetPlaceholderManager() *PlaceholderManager {
+	once.Do(func() {
+		if placeholderMgr == nil {
+			log.Logger().Fatal("PlaceholderManager is not initiated")
+		}
+	})
+	return placeholderMgr
+}
+
+func (mgr *PlaceholderManager) createAppPlaceholders(app *Application) error {
+	mgr.Lock()
+	defer mgr.Unlock()
+
+	// iterate all task groups, create placeholders for all the min members
+	for _, tg := range app.getTaskGroups() {
+		for i := int32(0); i < tg.MinMember; i++ {
+			placeholderName := utils.GeneratePlaceholderName(tg.Name, app.GetApplicationID(), i)
+			placeholder := newPlaceholder(placeholderName, app, tg)
+			// create the placeholder on K8s
+			_, err := mgr.clients.KubeClient.Create(placeholder.pod)
+			if err != nil {
+				// if failed to create the place holder pod
+				// caller should handle this error
+				log.Logger().Error("failed to create placeholder pod",
+					zap.Error(err))
+				return err
+			}
+			log.Logger().Info("placeholder created",
+				zap.String("placeholder", placeholder.String()))
+		}
+	}
+
+	return nil
+}
+
+// clean up all the placeholders for an application
+func (mgr *PlaceholderManager) CleanUp(app *Application) {
+	log.Logger().Info("start to clean up app placeholders",
+		zap.String("appID", app.GetApplicationID()))
+	for taskID, task := range app.taskMap {
+		if task.GetTaskPlaceholder() {
+			// remove pod
+			err := mgr.clients.KubeClient.Delete(task.pod)
+			if err != nil {
+				log.Logger().Error("failed to clean up placeholder pod",
+					zap.Error(err))
+				mgr.orphanPod[taskID] = task.pod
+			}
+		}
+	}
+	log.Logger().Info("finish to clean up app placeholders",
+		zap.String("appID", app.GetApplicationID()))
+}
+
+func (mgr *PlaceholderManager) cleanOrphanPlaceholders() {
+	mgr.Lock()
+	defer mgr.Unlock()
+	for taskID, pod := range mgr.orphanPod {
+		log.Logger().Debug("start to clean up orphan pod",
+			zap.String("taskID", taskID),
+			zap.String("podName", pod.Name))
+		err := mgr.clients.KubeClient.Delete(pod)
+		if err != nil {
+			log.Logger().Warn("failed to clean up orphan pod", zap.Error(err))
+		} else {
+			delete(mgr.orphanPod, taskID)
+		}
+	}
+}
+
+func (mgr *PlaceholderManager) Start() {
+	log.Logger().Info("starting the Placeholder Manager")
+	mgr.stopChan = make(chan struct{})
+	if mgr.isRunning() {
+		log.Logger().Info("The placeholder manager has been started")
+		return
+	}
+	mgr.setRunning(true)
+	go func() {
+		for {
+			select {
+			case <-mgr.stopChan:
+				log.Logger().Info("PlaceholderManager has been stopped")
+				mgr.setRunning(false)
+				return
+			default:
+				// clean orphan placeholders every 5 seconds
+				log.Logger().Info("clean up orphan pod")
+				mgr.cleanOrphanPlaceholders()
+				time.Sleep(5 * time.Second)
+			}
+		}
+	}()
+}
+
+func (mgr *PlaceholderManager) Stop() {
+	if !mgr.isRunning() {
+		log.Logger().Info("The placeholder manager has been stopped")
+		return
+	}
+	log.Logger().Info("stopping the Placeholder Manager")
+	mgr.stopChan <- struct{}{}
+	time.Sleep(3 * time.Second)

Review comment:
       When we send the `struct{}{}` to  `stopChan`, the `Start()` might not set Running to false immediately.
   Or we can move sleep to `TestPlaceholderManagerStartStop()`, which is located in `placeholder_manager_test.go`.




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