Auto Scaling:Automatically add and remove ECS instances from a PolarDB cluster whitelist

Create a policy

1. Log on to the RAM console.

2. In the left-side navigation pane, choose Permissions > Policies.

3. Click Create Policy.

4. On the Create Policy page, click the JSON tab, enter the following policy document, and click OK. Set the policy name to ESSHookPolicyForPolarDBWhitelist.

   {
       "Version": "1",
       "Statement": [
           {
               "Action": [
                   "ecs:DescribeInstances"
               ],
               "Resource": "*",
               "Effect": "Allow"
           },
           {
               "Action": [
                   "polardb:DescribeDBClusterAccessWhitelist",
                   "polardb:ModifyDBClusterAccessWhitelist"
               ],
               "Resource": "*",
               "Effect": "Allow"
           },
           {
               "Action": [
                   "ess:CompleteLifecycleAction"
               ],
               "Resource": "*",
               "Effect": "Allow"
           }
       ]
   }

Attach the policy to the OOS RAM role

1. In the left-side navigation pane, choose Identities > Roles.

2. Find OOSServiceRole and click Grant Permission in the Actions column.

3. In the Grant Permission panel, configure the following settings and click Grant permissions.

   Parameter	Value
   Resource Scope	Account
   Policies	ESSHookPolicyForPolarDBWhitelist

Create the lifecycle hook

1. Log on to the Auto Scaling console.

2. In the left-side navigation pane, click Scaling Groups.

3. In the top navigation bar, select the region where your scaling group is located.

4. Click the ID of the scaling group, or click Details in the Actions column.

5. On the scaling group details page, click the Lifecycle Hook tab.

6. Click Create Lifecycle Hook.

7. Configure the following settings and click OK.

   Parameter	Value
   Name	ESSHookForAddPolarDBWhitelist
   Scaling Activity	Scale-out Event
   Timeout Period	300 (seconds). Set this to a value long enough for the OOS template to complete. If the OOS task does not finish before the timeout expires, the default execution policy takes effect.
   Default Execution Policy	Select Continue.
   Send Notification When Lifecycle Hook Takes Effect	Select OOS Template, then select Public Templates, and select ACS-ESS-LifeCycleModifyPolarDBIPWhitelist.

8. In the ACS-ESS-LifeCycleModifyPolarDBIPWhitelist template parameters, configure the following:

   Parameter	Value
   dbClusterId	The ID of your PolarDB cluster
   modifyMode	Append (adds private IP addresses to the whitelist during scale-out)
   OOSAssumeRole	OOSServiceRole

Trigger a scale-out event

Trigger a scale-out event by executing a scaling rule. You can also use scheduled tasks or event-triggered tasks to trigger scale-out events.

Note: Lifecycle hooks take effect only when scaling events are triggered by scaling rules, scheduled tasks, or event-triggered tasks. They do not take effect when you manually add or remove ECS instances from a scaling group.

1. On the scaling group details page, click the Scaling Rules and Event-triggered Tasks tab.

2. On the Scaling Rules tab, click Create Scaling Rule.

3. Configure the following settings and click OK.

   Parameter	Value
   Rule Name	Add1
   Rule Type	Simple Scaling Rule
   Operation	Add 1 Instances

4. Find the Add1 scaling rule and click Execute in the Actions column.

5. In the confirmation dialog, click OK.

After the scaling rule executes, Auto Scaling adds one ECS instance to the scaling group. The instance enters Pending Add state because the lifecycle hook is in effect. During the timeout period, OOS runs the ACS-ESS-LifeCycleModifyPolarDBIPWhitelist template to add the instance's private IP address to the PolarDB cluster's IP address whitelist.