Auto Scaling:Use scaling configuration features to enable automatic scaling

Feature description

Step 1: Prepare feature settings

This section describes how to prepare an instance RAM role, tags, an SSH key pair, and the instance user data.

1. Create tags.

   For more information, see Create or add a tag.

2. Create an SSH key pair.

   For more information, see Create an SSH key pair.

3. Create a 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 specify an existing RAM role in a scaling configuration, make sure that ECS or Elastic Container Instance is the trusted entity of the RAM role. Otherwise, Auto Scaling cannot create ECS instances or elastic container instances based on the scaling configuration. For example, RAM role AliyunECSImageExportDefaultRole grants the permission of exporting images. The trust policy of the RAM role allows all ECS instances in the current account to assume this RAM role. Sample code:

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

   Note

   ecs.aliyuncs.com specifies that all ECS instances of the current account can assume the RAM role.

4. Prepare user data.

   For more information, see Instance user data.

   The following code shows a sample Shell script that enables Auto Scaling to write Hello World. The time is now{current time} to the /root/output10.txt file upon the first instance startup. Sample script:

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

   Note

   The Shell script used in this example is simple and only for reference. You can create a more advanced custom script to implement more features upon instance startups based on your business requirements.

   The following code shows the result of the Base64 encoding of the preceding code:

   IyEvYmluL3NoDQplY2hvICJIZWxsbyBXb3JsZC4gIFRoZSB0aW1lIGlzIG5vdyAkKGRhdGUgLVIpISIgfCB0ZWUgL3Jvb3Qvb3V0cHV0MTAudHh0 

Step 2: Apply the feature settings

This section describes how to create a scaling group and a scaling configuration, and apply the feature settings that are prepared in Step 1: Prepare feature settings to the scaling configuration.

1. Create a scaling group.

   For more information, see Manage scaling groups.

   The following table describes the parameters that you must configure when you create a scaling group.

   Parameter	Description
   Minimum Number of Instances	In this example, this parameter is set to 1. After you enable the scaling group, Auto Scaling automatically creates one ECS instance in the scaling group.
   Instance Configuration Source	In this example, Create from Scratch is selected.
   Network Type	In this example, VPC is selected. Note This parameter is available only for scaling groups of the ECS type.
   VPC	Specify the ID of an existing virtual private cloud (VPC).
   vSwitch	Select a vSwitch that resides in the specified VPC.

2. Create and enable a scaling configuration.

   For more information, see Create a scaling configuration of the ECS type.

   The following table describes the parameters that you must configure when you create a scaling configuration.

   Section	Parameter	Description
   Instance and Image	Select Image	In this example, Ubuntu 16.04 64-bit below the Public Images field is selected.
   Management Settings	Logon Credentials	In this example, Key Pair is selected.
   	Key pair	Select the key pair that was created in Step 1: Prepare feature settings.
   	Tag	Select the tags that were created in Step 1: Prepare feature settings.
   Advanced Settings	RAM Role	Select the RAM role that was created in Step 1: Prepare feature settings.
   	Instance User Data	Pass the script that was prepared in Step 1: Prepare feature settings.

3. Enable the scaling group.

   For more information, see Enable a scaling group.

Step 3: Verify the feature settings

In Step 2, the Minimum Number of Instances parameter was set to 1. After you enable the scaling group, Auto Scaling creates one ECS instance to ensure that the minimum number of instances is reached.

1. View the automatically created ECS instance.

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

2. In the row of the ECS instance, click the ID or name of the ECS instance whose details you want to view.

   The following figure shows an example of the instance details page. In the figure, the RAM role and tag settings of the ECS instance are in effect.

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

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

   The following figure shows an example of a successful logon. In the figure, the SSH key pair is in effect.

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

   cat /root/output10.txt

   The following figure shows an example of the file content. In this figure, the instance user data feature is in effect.