Modifying an AS Group

Scenarios

You can modify an AS group if needed. The settings of the following parameters can be changed: Name, Max. Instances, Min. Instances, Expected Instances, Health Check Method, Health Check Interval, Instance Removal Policy, Cooldown Period, and Multi-AZ Scaling Policy.

Changing the value of Expected Instances will trigger a scaling action. AS will automatically increase or decrease the number of instances to the value of Expected Instances.

Constraints

• If the AS group is not enabled, contains no instance, and has no scaling action ongoing, you can modify Subnet configurations.
• If an AS group has no scaling action ongoing, you can modify its AZ and Load Balancing configurations.

Procedure

1. Log in to the AS console.
2. Modify an AS group.
   You can modify an AS group using either of the following methods:

   • Locate the row that contains the target AS group and choose More > Modify AS Group in the Operation column.

     

   • Click the name of the target AS group. In the upper right corner of the Overview page, click Modify AS Group.

     

3. In the displayed dialog box, modify the parameters of the AS group.
   Figure 1 Modifying AS group parameters
   

   

   Table 1 AS group parameters

   Parameter	Description	Example
   Name	Specifies the name of the AS group. The name contains 1 to 64 characters and consists of only letters, digits, underscores (_), and hyphens (-).	-
   Max. Instances	Specifies the maximum number of ECS instances in an AS group.	1
   Expected Instances	Specifies the expected number of ECS instances in an AS group. After an AS group is created, you can change this value, which will trigger a scaling action. The number of expected instances must be greater than or equal to the minimum number of instances and less than or equal to the maximum number of instances.	0
   Min. Instances	Specifies the minimum number of ECS instances in an AS group.	0
   Cooldown Period	A cooldown period (in seconds) is the period of time between two scaling actions. AS recounts the cooldown period after a scaling action is complete. During the cooldown period, AS denies all scaling requests triggered by alarm-based policies. Scaling requests triggered manually or by scheduled or periodic policies are not affected.	300
   AZ	An availability zone is also called an AZ. An AZ is a physical location with independent power supply and networks within a region. AZs in the same region can communicate with each other over an internal network. Different AZs are physically isolated. If you require high availability, create servers in different AZs. If you require low network latency, create servers in the same AZ.	-
   Multi-AZ Scaling Policy	This parameter can be set to Balanced or Sequenced. Balanced: When scaling out an AS group, the system preferentially distributes ECS instances evenly across AZs used by the AS group. If it fails in the target AZ, it automatically selects another AZ based on the sequenced policy. Sequenced: When scaling out an AS group, the system distributes ECS instances to the AZs according to the order in which AZs are specified. NOTE: This parameter is mandatory only when two or more AZs are selected.	Balanced
   Subnet	You can select up to five subnets. The AS group automatically binds all NICs to the created ECS instances. The first subnet is used by the primary NIC of an ECS instance by default, and other subnets are used by extension NICs of the ECS instance.	-
   Load Balancing	This parameter is optional. A load balancer automatically distributes traffic across all ECS instances in an AS group to balance their loads. It improves the fault tolerance of your applications and expands application capabilities. NOTE: Up to six load balancers can be added to an AS group. Only a created load balancer can be bound to an AS group, and the AS group and load balancer must be in the same VPC. Adding multiple load balancers allows you to monitor multiple services simultaneously, improving service scalability. If ELB health check is selected for Health Check Method, when any one of the listeners detects that an ECS instance becomes unhealthy, AS will replace it with a functional one. If you select Elastic load balancer, configure the following parameters: Load Balancer Backend ECS Group Backend Port: specifies the port on which a backend ECS listens for traffic. Weight: determines the portion of requests a backend ECS processes compared to other backend ECSs added to the same listener. IP Version: specifies the version of instance IP address to be associated with the load balancer. The value can be IPv4 or IPv6. For more information about load balancing, see Elastic Load Balance User Guide.	-
   Health Check Method	If an ECS instance fails a health check, AS replaces it with a new one. Health check methods: ECS health check: checks the ECS instance status. If an ECS instance is stopped or deleted, it is considered unhealthy. This method is selected by default. Using this method, the AS group periodically checks the status of each ECS instance. If an ECS instance is unhealthy, AS removes the ECS instance from the AS group. Both of the preceding health check methods remove unhealthy instances from an AS group. For more information about the rules regarding whether to delete instances, see Table 1.	-
   Health Check Interval	Specify the interval between health checks. You can set a health check interval (10 seconds, 1 minute, 5 minutes, 15 minutes, 1 hour, or 3 hours) based on service requirements.	5 minutes
   Health Check Grace Period	Specifies the health check grace period for instances in an AS group. The unit is seconds and the value range is 0 to 86,400. The default value is 600. The health check grace period starts only after an instance is added to an AS group and enabled. The AS group will start checking the instance status only after the grace period ends. This parameter is available only if the ELB health check method is selected for the AS group.	600
   Instance Removal Policy	Controls which instances are first to be removed during scale in. If specified conditions are met, scaling actions are triggered to remove instances by following the removal policy you choose. There are four instance removal policies for you to choose from: Oldest instance created from oldest AS configuration: The oldest instance created from the oldest configuration is removed from the AS group first. Newest instance created from oldest AS configuration: The newest instance created from the oldest configuration is removed from the AS group first. Oldest instance: The oldest instance is removed from the AS group first. Newest instance: The newest instance is removed from the AS group first. NOTE: Manually added ECS instances are the last to be removed. If AS does remove a manually added instance, it only removes the ECS instance from the AS group. It does not delete the instance. If multiple manually added ECS instances must be removed, AS preferentially removes the earliest-added instance first.	Oldest instance created from oldest AS configuration
   Enterprise Project	Specifies the enterprise project that the AS group belongs to. If an enterprise project is configured for an AS group, ECSs created in this AS group also belong to this enterprise project. If you do not specify an enterprise project, the default enterprise project will be used. NOTE: Value default indicates the default enterprise project. Resources that are not allocated to any enterprise projects under your account are displayed in the default enterprise project. Enterprise project is an upgraded version of IAM. It allocates and manages resources of different projects.	-
   Data Disk	If Data Disk is configured in the AS configuration used by the AS group, a data disk will be automatically created and attached to the ECS instances added during a scaling action to the AS group. If you select Delete, the data disks attached to an ECS instance will be deleted when the instance is removed from the AS group. Otherwise, the system only detaches the data disks from the ECS instance, but does not delete them when the instance is removed from the AS group.	-
   Agency	This parameter is optional. When your ECS resources in an AS group need to be shared with other accounts or delegated to professional personnel or teams for management, the tenant administrator can create an agency in IAM and grant the ECS management permissions to them. The delegated account can log in to the cloud system and switch to your account to manage resources. You do not need to share security credentials such as passwords with the account, ensuring the security of your account. If you have created an agency in IAM, select the agency from the drop-down list. For more information about agencies, see Delegating Another Account for Resource Management.	-

4. Click OK.