aws ecs 使用application autoscaling自动扩缩ecs服务

news2024/11/18 19:59:10

参考资料

https://aws.amazon.com/cn/blogs/china/microservices-on-amazon-ecs-1/
https://aws.amazon.com/cn/blogs/china/microservices-on-amazon-ecs-2/
https://zhuanlan.zhihu.com/p/355383555
https://docs.amazonaws.cn/en_us/AmazonECS/latest/developerguide/service-auto-scaling.html

ecs在两个层面上支持自动扩缩，即实例层面和服务层面

关于实例层面的扩缩容，是通过为ecs集群设置capacity provider实现的，本质上其实是一个ec2 autoscaling 组，通过设置cw告警和事件，实现集群实例的扩缩容。这篇文档对原理解释的很清楚
关于服务层面的扩缩容，是通过application autoscaling 服务完成的，该服务可以与很多其他的aws服务集成，但是控制台无法查看此信息，可以通过describe-scalable-targets api查看

ecs支持通过autoscaling来自动扩缩服务中所需的任务数量，在服务创建过程或者更新过程中进行设置，界面如下，中国区缺少一些选项。

只能使用平均值发布cw指标
支持的自动伸缩策略有限，推荐 Target tracking 策略
用于自动扩缩的角色为AWSServiceRoleForApplicationAutoScaling _ ECSService
自动扩缩的起点并非设置的desired count，而是实际的任务数量
如果所需数量超过最大数，则首先调整实际数量到最大数，再按照缩放规则缩放。所需数量小于最小值时同理
支持从0扩展
在服务部署期间会停止缩容，但是扩容不会停止，除非主动暂停

在这里插入图片描述

自动扩容

为应用程序施压

$ webbench -c 100 -t 600  http://172.31.20.73/

在这里插入图片描述

由于cpu使用率超过50的目标值，导致cw触发告警并执行扩容操作

2023-02-27 09:18:47	State update	Alarm updated from In alarm to OK.
2023-02-27 09:06:47	Action	Successfully executed action arn:aws-cn:autoscaling:cn-north-1:xxxxxxxx:scalingPolicy:20be5a77-1b23-494c-a9d5-1d21aec6ed61:resource/ecs/service/workfargate/nginx-svc:policyName/testnginx-autoscale:createdBy/63002f92-e64f-484d-a9f5-1035324563ba

扩容后，service事件显示如下启动信息

Message: Successfully set desired count to 3. Change successfully fulfilled by ecs. Cause: monitor alarm TargetTracking-service/workfargate/nginx-svc-AlarmHigh-75d51541-0ab8-4db4-9606-6b204c846c6e in state ALARM triggered policy testnginx-autoscale

由于最大数量为5，因此扩容最大只能到5无法超过

自动缩容

由于cpu使用率过低，导致cw触发告警并执行缩减操作

2023-02-27 09:06:47	Action	Successfully executed action arn:aws-cn:autoscaling:cn-north-1:xxxxx:scalingPolicy:20be5a77-1b23-494c-a9d5-1d21aec6ed61:resource/ecs/service/workfargate/nginx-svc:policyName/testnginx-autoscale:createdBy/63002f92-e64f-484d-a9f5-1035324563ba
2023-02-27 09:06:47	State update	Alarm updated from Insufficient data to In alarm.

缩减后，停止pod的last status中会显示如下信息

STOPPED (Scaling activity initiated by (deployment ecs-svc/3120824563093745023))

在service的事件中存在以下记录

Message: Successfully set desired count to 1. Change successfully fulfilled by ecs. Cause: monitor alarm TargetTracking-service/workfargate/nginx-svc-AlarmLow-99c588d3-d004-42f6-a10d-67d20c48a4c1 in state ALARM triggered policy testnginx-autoscale

由于min数量为1，因此最小缩容到1个任务

缩减到0的事件

Message: Successfully set desired count to 0. Change successfully fulfilled by ecs. Cause: monitor alarm TargetTracking-service/workfargate/nginx-svc-AlarmLow-99c588d3-d004-42f6-a10d-67d20c48a4c1 in state ALARM triggered policy testnginx-autoscale

其他线索

由于服务数量是由application触发的扩缩容操作，通过cloudtrail查看触发的具体api操作

{
    "eventVersion": "1.08",
    "userIdentity": {
        "type": "AssumedRole",
        "principalId": "AROAQRIBWRJKAGUKQLRHZ:AutoScaling-UpdateDesiredCapacity",
        "arn": "arn:aws-cn:sts::xxxxxxx:assumed-role/AWSServiceRoleForApplicationAutoScaling_ECSService/AutoScaling-UpdateDesiredCapacity",
        "invokedBy": "ecs.application-autoscaling.amazonaws.com"
    },
    "eventSource": "ecs.amazonaws.com",
    "eventName": "UpdateService",
    "awsRegion": "cn-north-1",
    "sourceIPAddress": "ecs.application-autoscaling.amazonaws.com",
    "userAgent": "ecs.application-autoscaling.amazonaws.com",
    "requestParameters": {
        "cluster": "workfargate",
        "desiredCount": 3,
        "forceNewDeployment": false,
        "service": "nginx-svc"
    }
}