Use scaling configuration features to implement auto scaling

Scaling configuration features

Step 1: Create the configuration items

Follow these steps to create the required instance RAM role, tags, key pair, and instance user data.

1. Create a tag.

   For more information, see Create and bind tags.

2. Create a key pair.

   For more information, see Create an SSH key pair.

3. Create an instance RAM role.

   For more information, see Create a RAM role for a trusted Alibaba Cloud service. You can also use an existing RAM role. When you select an instance RAM role in a scaling configuration, ensure that the permission policy of the instance RAM role allows instances in the scaling group to assume the role. Otherwise, the scaling configuration cannot launch instances. For example, the RAM role AliyunECSImageExportDefaultRole is used to authorize image exports and allows all ECS instances of the current user to assume this role. Its trust policy is as follows:

   {
       "Statement": [
           {
               "Action": "sts:AssumeRole",
               "Effect": "Allow",
               "Principal": {
                   "Service": [
                       "ecs.aliyuncs.com"
                   ]
               }
           }
       ],
       "Version": "1"
   }

   Note

   ecs.aliyuncs.com indicates that all ECS instances that belong to the current user can assume this RAM role.

4. Generate the instance user data.

   For more information, see Overview of instance user data.

   In this example, a Shell script is created to write the string Hello World. The time is now{current time} to the /root/output10.txt file after the instance starts for the first time. The script is as follows:

   #!/bin/sh
   echo "Hello World.  The time is now $(date -R)!" | tee /root/output10.txt

   Note

   The shell script in this example is simple. You can customize the script to perform more complex tasks when an instance starts.

   After you Base64-encode the script, the content is as follows:

   IyEvYmluL3NoDQplY2hvICJIZWxsbyBXb3JsZC4gIFRoZSB0aW1lIGlzIG5vdyAkKGRhdGUgLVIpISIgfCB0ZWUgL3Jvb3Qvb3V0cHV0MTAudHh0 

Step 2: Apply the configuration items

Follow these steps to create a scaling group and a scaling configuration, and then apply the items created in Step 1.

1. Create a scaling group.

   For more information, see Create a scaling group.

   When you create the scaling group, take note of the following parameters:

   Parameter	Description
   Minimum Number of Instances	Set this to 1. After the scaling group is enabled, Auto Scaling automatically creates one instance.
   Instance Configuration Source	Select Create from Scratch.
   Network Type	Select VPC. Note This parameter applies only to scaling groups for ECS instances and is not available for scaling groups for ECI instances.
   VPC	Select the ID of an existing VPC.
   vSwitch	Select a vSwitch.

2. Create and enable a scaling configuration.

   For more information, see Create a scaling configuration for ECS instances.

   When you create the scaling configuration, take note of the following parameters:

   Section	Parameter	Description
   Instance and image	Image	Select Ubuntu 16.04 64-bit from the Public Image.
   Management Settings	Logon Credential	Select Key Pair.
   	Key Pair	Select the key pair that you created in Step 1: Create the configuration items.
   	Tag	Select the tag that you created in Step 1: Create the configuration items.
   Advanced Settings	Instance RAM Role	Select the instance RAM role that you created in Step 1: Create the configuration items.
   	The user data of the instance.	Enter the instance user data script that you prepared in Step 1: Create the configuration items.

3. Enable the scaling group.

   For more information, see Enable a scaling group.

Step 3: Verify the custom configurations

Because you set Minimum Number of Instances to 1, Auto Scaling creates one instance (an ECS instance in this example) when the scaling group is enabled, which ensures that the group meets its minimum instance requirement.

1. View the automatically created ECS instance.

   For more information, see View instances in a scaling group.

2. In the ECS Instance ID/Name column, click the instance ID to view the details of the ECS instance.

   The instance details show that the tag and instance RAM role from the scaling configuration have been applied. On the instance details page, go to the Tags section and verify that the instance has tags such as bw:ecs and acs:autoscaling:scalingGroupId:a***yn attached. This confirms the tag configuration was successful. Then, go to the Other Information section and check that RAM Role displays the name of the role you configured, such as AliyunECSImageImportDefaultR.... This confirms that the instance RAM role is successfully attached to the ECS instance.

3. Use the SSH key pair to log on to the instance.

   For more information, see Connect to a Linux instance by using an SSH key pair.

   A successful logon, indicated by the following output, confirms that the SSH key pair was configured correctly.

   Using username "root".
   Authenticating with public key "imported-openssh-key"
   Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 4.4.0-151-generic x86_64)
    * Documentation:  https://help.ubuntu.com
    * Management:     https://landscape.canonical.com
    * Support:        https://ubuntu.com/advantage
   Welcome to Alibaba Cloud Elastic Compute Service !
   root@ixxxxxxxxxx:~#

4. Run the following command to view the content of the /root/output10.txt file:

   cat /root/output10.txt

   The following output shows the file content, which indicates that the instance user data configuration has taken effect:

   root@ixxx:~# cat /root/output10.txt
   Hello World.  The time is now Mon, 16 Sep 2019 11:01:26 +0800!
   root@ixxx:~#