Add ECS instances to an application that is deployed in an ECS cluster - Enterprise Distributed Application Service

If the Elastic Compute Service (ECS) instances deployed for an application are overloaded or no instance is available for this application, you can add instances to scale out this application. Enterprise Distributed Application Service (EDAS) provides three scale-out modes. You can select instances from the cluster in which the application is deployed, purchase instances based on existing instance specifications, or purchase instances based on an instance launch template.

Status of added ECS instances

The status of the ECS instances that are added depends on the status of the application before the scale-out.

If the application has been deployed and is running before the scale-out, the application is automatically deployed on the added ECS instances. The added ECS instances start and run the application.
If the application has been deployed but stopped before the scale-out, the application is automatically deployed on the added ECS instances. The added ECS instances start and run the application.
If the application has not been deployed before the scale-out, the application is not deployed on the added ECS instances. The added ECS instances are stopped.

Start a scale-out

Log on to the EDAS console.
In the left-side navigation pane, choose Application Management > Applications. In the top navigation bar, select the region. In the upper part of the Applications page, select the microservice namespace from the Microservice Namespace drop-down list and then click the name of the desired application.
Click an application. On the application details page, click Scale Out in the upper-right corner. In the Add Instance dialog box, set the Target Group parameter in the Scale-out Method step.
Set the Scale-out Method parameter and perform the subsequent steps.

Select from Clusters Deployed with the Application

You can select idle instances from the cluster in which the application resides and add them to the application.

Select Select from Clusters Deployed with the Application for the Scale-out Method parameter.
In the instance list, select idle instances for the scale-out and click Scale Out.
After the The application is scaled out message appears, go to the Instance Information tab to view the status of the added instances. If the status is Normal, the scale-out is successful.

Purchase Based on Existing Instance Specifications

You can use an instance in the cluster in which the application resides as the specification template to purchase ECS instances for the scale-out.

Select Purchase Based on Existing Instance Specifications for the Scale-Out Method parameter. All instances in the cluster in which the application resides are listed.
Select the instance that you want to use as the specification template. Set the Recycling Mode parameter and click Next.
Note The purchased ECS instances have the same configurations as the selected existing ECS instance, including the instance type, disks, network, user data, and tags.
In the Purchase Details step, set the Quantity and Password parameters, select Elastic Compute Service Terms of Service Terms of Service for Images, and then click Next.
In the Confirm step, view the information about the instances to purchase, and click Confirm.
In the upper part of the page, the Automatic purchasing is triggered. Check the real-time information in the application change process message appears.
Click the Instance Information tab and view the status of the added instances. If the status is Normal, the scale-out is successful.

Note

An ECS instance purchase based on the specifications of an existing ECS instance includes two change processes. EDAS purchases ECS instances, and then the purchased ECS instances are automatically added to the application.
The scale-out starts in about three minutes after you submit a request. The interval between the two change processes is about 10 seconds.
All billing details are subject to regular billing rules of ECS and EDAS. You are not charged for this operation.
By default, EDAS uses the AccessKey pair that you specified to log on to the ECS instances.

Purchase Based on Instance Launch Template

You must create an instance launch template in the ECS console in advance. Then, you can purchase ECS instances based on the launch template in the EDAS console. For more information about how to create an instance launch template, see Create a launch template.

Important The created instance launch template and your application must be in the same virtual private cloud (VPC). Otherwise, you cannot select the created instance launch template.

Select Purchase Based on Instance Launch Template for the Scale-Out Method parameter.
Select the template that you want to use and the template version, and set the Recycling Mode parameter. Then, click Next.
- Use Bound Template: Use an instance launch template that is bound to the instance group. For more information, see Associate a launch template with an application instance group.
- Use Specified Template: Use an instance launch template that is created in the ECS console. If you have created multiple templates, you must select a specific template and a version.
In the Purchase Details step, set the Quantity parameter, select Elastic Compute Service Terms of Service Terms of Service for Images, and then click Next.
In the Confirm step, check the quantity of ECS instances to be purchased and the information about the instance launch template. Verify all the information and click Confirm.
In the upper part of the page, the Automatic purchasing is triggered. Check the real-time information in the application change process message appears.
Click the Instance Information tab and view the status of the added instances. If the status is Normal, the scale-out is successful.

Additional information

You can use the auto scaling feature to adjust the number of ECS instances for an application. For more information, see Perform auto scaling on applications in ECS clusters.