If the Elastic Compute Service (ECS) instances deployed with 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 where the application is deployed, purchase instances based on the existing instance specifications, or purchase instances based on the instance startup template.

Running status of instances to be added

The running status of the ECS instances that you want to add depends on the running status of the application.
  • If the application has been deployed and is running before scale-out, it is automatically deployed, started, and run on the added ECS instances.
  • If the application has been deployed and stopped before scale-out, it is automatically deployed, started, and run on the added ECS instances.
  • If the application has not been deployed before scale-out, it is not automatically deployed, started, or run on the added ECS instances, and the added instances are stopped.

Start scale-out

  1. Log on to the EDAS console.
  2. In the left-side navigation pane, click Applications. In the top navigation bar, select a region. In the upper part of the page, select a namespace. On the Applications page, click the name of the desired application.
  3. Click an application. On the Basic Information page, click Scale Out in the upper-right corner. In the Add an Instance dialog box, set Target Group on the Scale-Out Method tab.
  4. Select Scale-out Method and perform the subsequent steps.

From Cluster Select

You can select idle instances from the cluster where the application is located and add them to the application.

  1. Select From Cluster Select for Scale-Out Method.
  2. In the instance list, select an idle instance for the scale-out and click Scale Out.
    After the Scale-Out Success message appears, go to the Instance Information tab to view the running status of the added instance. If the status is Normal, the scale-out is successful.

Purchase Based on Existing Example Specifications

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

  1. Select Purchase Based on Existing Example Specifications for Scale-Out Method. All instances for the cluster where the application is located are listed.
  2. Select the instance that you want to use as the specification template. Click Release Modes, and then click Next.
    Note By default, the purchased ECS instance carries the same basic information as the selected existing ECS instance, such as the specifications, disks, network, user data, and tags.
  3. On the Purchase Details tab, set Purchase Quantity and Login Key, select ECS Service Terms | Image Service Terms, and then click Next.
  4. On the Confirm tab, view the information about the purchased instance, and click Confirm.
    On the top of the page, the "Automatic purchasing is triggered. Check the real-time information in the application change process." message appears.
  5. Click the Instance Information tab and view the running status of the added instance. If the status is Normal, the scale-out is successful.
Note
  • ECS instance purchasing based on the specifications of an existing ECS instance includes two change processes. EDAS purchases an ECS instance from ECS, and then the purchased ECS instance is 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 normal billing rules of ECS and EDAS. You are not charged for this operation.
  • The default ECS logon information is based on the AccessKey pair that you set. EDAS does not acquire your private information.

Purchase Based on Instance Startup Template

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

Notice The created instance startup template and your application must be in the same Virtual Private Cloud (VPC). Otherwise, you cannot select the created instance startup template.
  1. Select Purchase Based on Instance Startup Template for Scale-Out Method.
  2. Select the template that you want to bind and the template version, and select Release Modes. Then, click Next.
    • With Binding Template: the instance startup template that is bound to an instance group. For more information, see Bind an instance startup template.
    • With Specified Template: the template that is created in the ECS console. If you have created multiple templates, you must select a template and a version number.
  3. On the Purchase Details tab, set Purchase Quantity, select ECS Service Terms | Image Service Terms, and then click Next.
  4. On the Confirm tab, check the quantity of ECS instances that you want to purchase and the information about the instance startup template. Verify all the information and click Confirm.
    On the top of the page, the "Automatic purchasing is triggered. Check the real-time information in the application change process." page appears.
  5. Click the Instance Information tab and view the running status of the added instance. If the Normal state is displayed, the scale-out is successful.

References