结合CRaC技术实现JAVA类应用启动加速_容器计算服务(ACS)-阿里云帮助中心

Java类应用往往在启动时需要占用大量的资源进行预热（类加载及JIT编译）。成功运行后若遇到CrashBackOff事件导致Pod重启，应用重启又需要花费时间再次进行数据预热，这在生产环境中会不可避免地造成业务中断。容器计算服务 ACS（Container Compute Service）在实现柔性热变配以加速Java应用启动后，推出了基于CRaC技术的应用启动加速能力。本文介绍CRaC加速应用启动的原理，以及使用CRaC加速应用启动的场景。

背景信息

CRaC（Coordinated Restore at Checkpoint）技术是社区推出的一种用于提高Java类语言应用启动效率的技术，特别是在大型应用或者微服务架构。该技术通过优化程序的启动过程，将程序的数据和状态在特定点进行有效保存和恢复，从而减少重新加载和重建应用所需的时间。

工作原理

CRaC引入了“检查点”的概念，即从检查点原样恢复。通过将JVM的当前运行状态包括进程上下文、内存状态等进行持久化存储，相当于对JVM做了一次进程快照，这个状态称为CheckPoint。当业务进程异常退出后，服务可以通过快照文件快速恢复到运行状态。通过从检查点恢复的启动速度将明显快于传统的冷启动方式，从而减少应用启动时间。

CRaC基于CRIU（Checkpoint and Restore in Userspace）实现检查点和恢复功能。CRIU是一个在用户空间中实现检查点和恢复功能的项目，适用于Linux操作系统。CRaC在此基础上进行了增强和调整，结合容器柔性变配，可以进一步加快Java应用程序的启动速度。整体架构图如下。

技术优势

在ACS中使用CRaC技术，可以为您带来以下优势。

极简体验：简化了操作流程，快速上手并高效使用。
标准开放：遵循社区标准，确保兼容性和可扩展性。
极致弹性：通过智能调度和资源优化，确保应用在不同负载下的稳定性和性能。

注意事项

JDK版本限制：您需要将JDK更换为Alibaba Dragonwell 11的最新版本或者其他支持CRaC技术的JDK。
设置检查点：在代码或脚本中设置Checkpoint，属于侵入式修改，需要研发团队对CRaC技术有一定程度的了解。更多信息，请参见CRaC library。
- 所设置的检查点之前程序状态可重用。
- 所设置的检查点之前程序状态不可重用，在进程被恢复的时候，额外需要将这些状态数据或业务代码逻辑通过回调（Callback）的方式进行状态恢复。
为了配合柔性变配，最大化应用启动速度的优化效果，您可以为应用配置对应的JVM参数。具体操作，请参见Java应用启动加速的JVM参数配置。

场景实践

说明

本操作需要为ACS Pod开启特权模式，请提交工单开启。

场景一：对比使用/不使用CRaC技术在常规环境运行应用

本场景演示在不使用柔性变配的情况下，对比使用和不使用CRaC技术的Java应用Spring-Petclinic的启动耗时。

使用以下内容，创建spring-petclinic-crac.yaml。

展开查看YAML内容

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-petclinic-crac
  namespace: default
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: spring-petclinic-crac
  template:
    metadata:
      # annotations:  禁用柔性变配
      #   scaling.alibabacloud.com/enable-inplace-resource-resize: "true"
      creationTimestamp: null
      labels:
        alibabacloud.com/compute-class: general-purpose
        alibabacloud.com/compute-qos: default
        app: spring-petclinic-crac
    spec:
      containers:
      - env:
        # 程序被正常启动过程中，enable CRaC的CheckPoint能力
        - name: DO_CRAC_CHECKPOINT
          value: "true"
        # CheckPoint内容存在路径，针对容器环境建议是一个emptyDir
        - name: CRAC_IMAGE_DIR
          value: /home/crac
        image: registry-cn-hangzhou.ack.aliyuncs.com/ack-demo/quickstart-acs-petclinic-demo:alpha.3
        imagePullPolicy: IfNotPresent
        name: crac-container
        securityContext:
          privileged: true
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        resources:
          requests:
            cpu: "500m"          
            memory: "1Gi"        
          limits:
            cpu: "500m"          
            memory: "1Gi"
        volumeMounts:
        - mountPath: /home/crac
          name: crac-cache-volume
      restartPolicy: Always
      schedulerName: default-scheduler
      volumes:
      - emptyDir: {}
        name: crac-cache-volume

使用以下内容，创建spring-petclinic.yaml。

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-petclinic
  namespace: default
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: spring-petclinic
  template:
    metadata:
      # annotations:  禁用柔性变配
      #   scaling.alibabacloud.com/enable-inplace-resource-resize: "true"
      creationTimestamp: null
      labels:
        alibabacloud.com/compute-class: general-purpose
        alibabacloud.com/compute-qos: default
        app: spring-petclinic
    spec:
      containers:
      - name: crac-container
        image: registry-cn-hangzhou.ack.aliyuncs.com/ack-demo/quickstart-acs-petclinic-demo:alpha.3
        imagePullPolicy: IfNotPresent
        securityContext:
          privileged: true
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        resources:
          requests:
            cpu: "500m"          
            memory: "1Gi"        
          limits:
            cpu: "500m"          
            memory: "1Gi"
      restartPolicy: Always
      schedulerName: default-scheduler

部署应用。

kubectl apply -f spring-petclinic-crac.yaml && kubectl apply -f spring-petclinic.yaml

验证启动速度。

查看两个Deployment的运行状态。

kubectl get pod | grep spring-petclinic

预期输出：

spring-petclinic-64cb7xxxxx-xxxxx        1/1     Running   0   110m
spring-petclinic-crac-574cdxxxxx-xxxxx   1/1     Running   0   47m

查看两个Deployment的启动日志。

kubectl logs spring-petclinic-64cb7xxxxx-xxxxx --tail=5 && \
echo -e "\033[31m↑↑↑ No crac ↑↑↑\033[0m-------------------\033[32m↓↓↓ With crac ↓↓↓\033[0m" && \
kubectl logs spring-petclinic-crac-574cdxxxxx-xxxxx --tail=5

预期输出：

2025-01-21 06:50:34.521  INFO 9 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 13 endpoint(s) beneath base path '/actuator'
2025-01-21 06:50:35.035  INFO 9 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-01-21 06:50:35.036  INFO 9 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2025-01-21 06:50:37.022  INFO 9 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2025-01-21 06:50:37.098  INFO 9 --- [           main] o.s.s.petclinic.PetClinicApplication     : Started PetClinicApplication in 26.587 seconds (JVM running for 28.57)
↑↑↑ No crac ↑↑↑-------------------↓↓↓ With crac ↓↓↓
2025-01-21 06:50:38.312  INFO 109 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 13 endpoint(s) beneath base path '/actuator'
2025-01-21 06:50:38.628  INFO 109 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-01-21 06:50:38.629  INFO 109 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2025-01-21 06:50:40.700  INFO 109 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2025-01-21 06:50:40.792  INFO 109 --- [           main] o.s.s.petclinic.PetClinicApplication     : Started PetClinicApplication in 27.941 seconds (JVM running for 31.305)

为使用CRaC的工作负载创建checkpoint。
```
kubectl exec -it spring-petclinic-crac-574cdxxxxx-xxxxx  -- sh -c './checkpoint.sh'
```
说明
此处以演示为目的，因此将创建checkpoint的动作单独列出来。在实际生产环境中，您可以将创建checkpoint的动作自动化到应用容器中，以简化操作。

模拟异常退出。

kubectl exec -it spring-petclinic-64cb7xxxxx-xxxxx -- sh -c 'pid=`ps -ef | pgrep java` && kill -9 $pid' 
kubectl exec -it spring-petclinic-crac-574cdxxxxx-xxxxx -- sh -c 'pid=`ps -ef | pgrep java` && kill -9 $pid'

再次查看两个Deployment的日志。

kubectl logs spring-petclinic-64cb7xxxxx-xxxxx --tail=5 && \
echo -e "\033[31m↑↑↑ No crac ↑↑↑\033[0m-------------------\033[32m↓↓↓ With crac ↓↓↓\033[0m" && \
kubectl exec -it  spring-petclinic-crac-574cdxxxxx-xxxxx -- sh -c 'cat /home/app/app_start.log'

说明

使用Checkpoint restore的方式重启应用不会输出应用的日志，因此示例镜像中预置了计算restore时间的函数，此处使用读取函数输出的日志文件。

预期输出：

2025-01-21 02:32:36.254  INFO 9 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 13 endpoint(s) beneath base path '/actuator'
2025-01-21 02:32:36.821  INFO 9 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-01-21 02:32:36.822  INFO 9 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2025-01-21 02:32:38.858  INFO 9 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2025-01-21 02:32:38.950  INFO 9 --- [           main] o.s.s.petclinic.PetClinicApplication     : Started PetClinicApplication in 26.558 seconds (JVM running for 28.644)
↑↑↑ No crac ↑↑↑-------------------↓↓↓ With crac ↓↓↓
Checking application start at Thu Jan 21 02:32:54 UTC 2025
Start PetClinic Cost : 417 ms
Application started successfully at Thu Jan 21 02:32:54 UTC 2025
===========================================

可以看到，使用两个Deployment首次启动的时间几乎一致。在重启后，使用CRaC技术的Deployment启动速度远快于普通启动的Deployment。

场景二：对比使用CRaC技术在启用/不启用变配的环境下运行应用

本场景演示使用CRaC技术的Java应用在使用和不使用柔性变配的情况下的启动耗时。

使用以下内容，创建spring-petclinic-crac-resize.yaml。

展开查看YAML内容

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-petclinic-crac-resize
  namespace: default
spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: spring-petclinic-crac-resize
  template:
    metadata:
      annotations:  
        scaling.alibabacloud.com/enable-inplace-resource-resize: "true" # 开启柔性变配
        alibabacloud.com/startup-cpu-burst-factor: '2' #设置启动扩容倍数为2
        alibabacloud.com/startup-cpu-burst-duration-seconds: "30" #不填则默认在Pod Ready后30秒自动降配
      creationTimestamp: null
      labels:
        alibabacloud.com/compute-class: general-purpose
        alibabacloud.com/compute-qos: default
        app: spring-petclinic-crac-resize
    spec:
      containers:
      - env:
        # 程序被正常启动过程中，enable CRaC的CheckPoint能力
        - name: DO_CRAC_CHECKPOINT
          value: "true"
        # CheckPoint内容存在路径，针对容器环境建议是一个emptyDir
        - name: CRAC_IMAGE_DIR
          value: /home/crac
        image: registry-cn-hangzhou.ack.aliyuncs.com/ack-demo/quickstart-acs-petclinic-demo:alpha.3
        imagePullPolicy: IfNotPresent
        name: crac-container
        securityContext:
          privileged: true
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        resources:
          requests:
            cpu: "500m"          
            memory: "1Gi"        
          limits:
            cpu: "500m"          
            memory: "1Gi"
        volumeMounts:
        - mountPath: /home/crac
          name: crac-cache-volume
        readinessProbe:
            tcpSocket:
              port: 8080
            initialDelaySeconds: 20
            periodSeconds: 10
      restartPolicy: Always
      schedulerName: default-scheduler
      volumes:
      - emptyDir: {}
        name: crac-cache-volume

对比不使用变配的Deployment，这里使用场景一的spring-petclinic-crac.yaml。

部署应用。

kubectl apply -f spring-petclinic-crac-resize.yaml

验证启动速度。

查看两个Deployment的运行状态。

kubectl get pod | grep spring-petclinic-crac

预期输出：

spring-petclinic-crac-574cdxxxxx-xxxxx          1/1     Running   0          29m
spring-petclinic-crac-resize-6474cxxxxx-xxxxx   1/1     Running   0          32m

查看两个Deployment的启动日志。

kubectl logs spring-petclinic-crac-574cdxxxxx-xxxxx --tail=5 && \
echo -e "\033[31m↑↑↑ No resize ↑↑↑\033[0m-------------------\033[32m↓↓↓ With resize ↓↓↓\033[0m" && \
kubectl logs spring-petclinic-crac-resize-6474cxxxxx-xxxxx --tail=5

预期输出：

2025-01-23 05:50:16.564  INFO 109 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 13 endpoint(s) beneath base path '/actuator'
2025-01-23 05:50:17.346  INFO 109 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-01-23 05:50:17.347  INFO 109 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2025-01-23 05:50:19.848  INFO 109 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2025-01-23 05:50:19.936  INFO 109 --- [           main] o.s.s.petclinic.PetClinicApplication     : Started PetClinicApplication in 38.912 seconds (JVM running for 43.614)
↑↑↑ No resize ↑↑↑-------------------↓↓↓ With resize ↓↓↓
2025-01-23 05:48:28.334  INFO 108 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 13 endpoint(s) beneath base path '/actuator'
2025-01-23 05:48:28.793  INFO 108 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2025-01-23 05:48:28.794  INFO 108 --- [           main] DeferredRepositoryInitializationListener : Triggering deferred initialization of Spring Data repositories…
2025-01-23 05:48:29.940  INFO 108 --- [           main] DeferredRepositoryInitializationListener : Spring Data repositories initialized!
2025-01-23 05:48:29.981  INFO 108 --- [           main] o.s.s.petclinic.PetClinicApplication     : Started PetClinicApplication in 19.449 seconds (JVM running for 22.339)

可以看到，启用柔性变配后应用的首次启动时间大幅缩短。

为工作负载创建checkpoint。

kubectl exec -it spring-petclinic-crac-574cdxxxxx-xxxxx  -- sh -c './checkpoint.sh' 
kubectl exec -it spring-petclinic-crac-resize-6474cxxxxx-xxxxx  -- sh -c './checkpoint.sh'

模拟异常退出。

kubectl exec -it spring-petclinic-crac-574cdxxxxx-xxxxx -- sh -c 'pid=`ps -ef | pgrep java` && kill -9 $pid' 
kubectl exec -it spring-petclinic-crac-resize-6474cxxxxx-xxxxx -- sh -c 'pid=`ps -ef | pgrep java` && kill -9 $pid'

再次查看两个Deployment的日志。

kubectl exec -it spring-petclinic-crac-574cdxxxxx-xxxxx -- sh -c 'cat /home/app/app_start.log' && \
echo -e "\033[31m↑↑↑ No crac ↑↑↑\033[0m-------------------\033[32m↓↓↓ With crac ↓↓↓\033[0m" && \
kubectl exec -it spring-petclinic-crac-resize-6474cxxxxx-xxxxx -- sh -c 'cat /home/app/app_start.log'

预期输出：

Checking application start at Thu Jan 23 05:56:34 UTC 2025
Start PetClinic Cost : 440 ms
Application started successfully at Thu Jan 23 05:56:34 UTC 2025
===========================================
↑↑↑ No resize ↑↑↑-------------------↓↓↓ With resize ↓↓↓
Checking application start at Thu Jan 23 05:56:45 UTC 2025
Start PetClinic Cost : 349 ms
Application started successfully at Thu Jan 23 05:56:46 UTC 2025
===========================================

可以看到，同时使用CRaC技术，启用变配后启动速度同样比不启用变配的启动速度快。