Creating an AS Group

An AS group consists of a collection of ECS instances and AS policies that have similar attributes and apply to the same application scenario. An AS group is the basis for enabling or disabling AS policies and performing scaling actions. The pre-configured AS policy automatically adds or deletes instances to or from an AS group, or maintains a fixed number of instances in an AS group.

When creating an AS group, specify an AS configuration for it. Additionally, add one or more AS policies for the AS group.

Creating an AS group involves the configuration of the maximum, minimum, and expected numbers of instances and the associated load balancer.

ECS types available in different AZs may vary. When creating an AS group, choose an AS configuration that uses an ECS type available in the AZs used by the AS group.

• If the ECS type specified in the AS configuration is not available in any of the AZs used by the AS group, the following situations will occur:
  • If the AS group is disabled, it cannot be enabled.
  • If the AS group is enabled, its status will become abnormal when instances are added to it.
• If the ECS type specified in the AS configuration is only available in certain AZs used by the AS group, the ECS instances added by a scaling action are only deployed in the AZs where that ECS type is available. As a result, the instances in the AS group may not be evenly distributed.
• Before creating an AS group, you need to create the desired AS configuration.

1. Log in to the management console.
2. Click in the upper left corner to select a region and a project.
3. Under Compute, click Auto Scaling. In the navigation pane on the left, choose Instance Scaling.
4. On the Instance Scaling page, click Create AS Group.
5. Configure parameters, such as Name, Max. Instances, Min. Instances, and Expected Instances. Table 1 describes the key AS group parameters.
   Table 1 AS group parameters

   Parameter	Description	Example
   Region	A region is where the AS group is deployed.	-
   AZ	An AZ is a physical location where resources use independent power supply and networks. AZs are physically isolated but interconnected through an internal network. 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 needs to be configured when two or more AZs are selected.	Balanced
   Name	Specifies the name of the AS group to be created. 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
   AS Configuration	Specifies the required AS configuration for the AS group. An AS configuration defines the specifications of the ECS instances to be added to an AS group. The specifications include the ECS image and system disk size. You need to create the required AS configuration before creating an AS group.	-
   VPC	Provides a network for your ECS instances. All ECS instances in the AS group are deployed in this VPC.	-
   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.	-
   Source/Destination Check	Specifies whether the system checks the correctness of the source IP addresses contained in the packets sent by ECS instances. If this function is disabled, an ECS can process traffic not destined specially for it. Disable this function if the ECS functions as a SNAT server or has a virtual IP address bound. If this function is enabled, the system checks whether source IP addresses contained in the packets sent by ECS instances are correct. If the IP addresses are incorrect, the system does not allow the ECS instances to send the packets. This prevents packet spoofing and improves system security. By default, this function is enabled.	-
   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. After multiple load balancers are added to an AS group, multiple services can be concurrently listened to, thereby 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. For more information about load balancing, see Elastic Load Balance User Guide.	-
   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
   EIP	If EIP has been selected in the AS configuration of the AS group, an EIP is automatically bound to the ECS instance added by a scaling action to the AS group. If you select Release, the EIP bound to an ECS instance is released when the instance is removed from the AS group. Otherwise, the system unbinds the EIP from the instance, but does not release it when the instance is removed from the AS group.	-
   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 Release, 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.	-
   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. ELB health check: determines the ECS instance status using a load balancing listener. This health check method is only available if a load balancer is configured for the AS group. An ECS instance is considered healthy only when all associated listeners detect it as healthy. If a listener detects that the ECS instance is unhealthy, AS removes the instance from the AS group.	ECS health check
   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	New instances often need time (grace period) for a brief warm-up before they can pass a health check. 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. Specifies the health check grace period for instances in an AS group. The value ranges from 0 to 86,400 seconds, with a default value of 600. This parameter is only available if the ELB health check method is selected for the AS group.	600s
   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.	-
   Tag	If you have many resources of the same type, you can use tags to manage your resources. You can identify specified resources quickly using the tags allocated to them. Each tag contains a key and a value. You can specify the key and value for each tag. Key The key must be specified. The key must be unique to the AS group. The key can include up to 36 characters. It cannot contain non-printable ASCII characters (0–31) or the following characters: =*<>\,|/ Value The value is optional. A key can have only one value. The value can include up to 43 characters. It cannot contain non-printable ASCII characters (0–31) or the following characters: =*<>\,|/	-
   Agency	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.	-

6. After setting the parameters, click Create Now.
7. (Optional) Add an AS policy.
   1. Locate the row containing the target AS group and click View AS Policy in the Operation column.
   2. (Optional) Click Add AS Policy to create an AS policy for the newly created AS group. For more details about AS policies, see Overview.