This topic describes how to put an Elastic Compute Service (ECS) instance that is not needed for the moment into the Standby state. After an ECS instance in a scaling group is put into the Standby state, the weight of the ECS instance as a backend server of the Server Load Balancer (SLB) instance that is associated with the scaling group changes to zero. Auto Scaling does not check the health status of the ECS instances that are in the Standby state or release the ECS instances that are in the Standby state.

Background information

You can put an ECS instance into the Standby state by using one of the following methods:
  • Synchronously put the ECS instance into the Standby state: Auto Scaling receives and handles the request to put the ECS instance into the Standby state in the backend. If your scaling group contains a large amount of resources, the synchronization operation takes a long period of time. This may cause timeout errors. We recommend that you asynchronously put the ECS instance into the Standby state.
  • Asynchronously put the ECS instance into the Standby state: A scaling activity is immediately triggered after you select the Asynchronously Switch to Standby option in the Auto Scaling console. You can view the result of the scaling activity on the Scaling Activities tab. Compared with the synchronous operation, the asynchronous operation brings a better interactive experience to users.
After an ECS instance is put into the Standby state:
  • If an SLB instance is associated with the scaling group to which the ECS instance belongs, the weight of the ECS instance as the backend server of the SLB instance changes to zero.
  • The ECS instance remains in the Standby state until you manually move it out of the Standby state.
  • Auto Scaling stops managing the lifecycle of the ECS instance. You must manually manage the lifecycle of the ECS instance.
  • If a scale-in activity is triggered, Auto Scaling does not remove the ECS instance from the scaling group.
  • When the ECS instance is stopped or restarted, Auto Scaling does not update the health status of the ECS instance.
  • To release the ECS instance, you must first remove it from the scaling group.
  • If you delete the scaling group to which the ECS instance belongs, Auto Scaling removes the ECS instance from the scaling group and moves the instance out of the Standby state.
    Note If the lifecycle of the ECS instance is managed by the scaling group, the ECS instance is released when you delete the scaling group. If the lifecycle of the ECS instance is not managed by the scaling group, the ECS instance is not released and can run as expected. For more information about how to manage the lifecycle of ECS instances, see ECS instance lifecycle in a scaling group.
  • You can stop the ECS instance or modify its configurations. For example, you can perform the following operations:

Procedure

  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 a region.
  4. Find a scaling group and go to the details page of the scaling group. You can use one of the following methods to go to the details page:
    • Click the ID of the scaling group in the Scaling Group Name/ID column.
    • Click Details in the Actions column of the scaling group.
  5. In the upper part of the page, click the Instances tab.
  6. Select the source of an ECS instance.
    • To select an ECS instance that is automatically created, click the Auto Created tab.
    • To select an ECS instance that is manually added, click the Manually Added tab.
  7. Use one of the following methods to put one or more ECS instances into the Standby state:
    • Find the ECS instance that you want to put into the Standby state and click Switch to Standby in the Actions column.
    • Select multiple ECS instances that you want to put into the Standby state and click Switch to Standby in the lower part of the Instances tab.
  8. In the Switch to Standby dialog box, select a method to put the ECS instance into the Standby state.
    • Synchronously put the ECS instance into the Standby state: Click OK.
    • Asynchronously put the ECS instance into the Standby state: Select Asynchronously Switch to Standby, and then click OK.

      On the Scaling Rules and Activities tab, click Scaling Activities and check whether the instance is put into the Standby state.