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- What's New
- Function Overview
- Service Overview
- Getting Started
- User Guide
- Best Practices
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API Reference
- Before You Start
- API Overview
- Calling APIs
- Getting Started
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APIs
- AS Groups
- AS Configurations
- Instances
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AS Policies
- Creating an AS Policy
- Creating an AS Policy (V2)
- Modifying an AS Policy
- Modifying an AS Policy (V2)
- Querying AS Policies Bound to an AS Group
- Querying AS Policies Bound to a Scaling Resource (V2)
- Querying AS Policies (V2)
- Querying an AS Policy
- Querying an AS Policy (V2)
- Executing, Enabling, or Disabling an AS Policy
- Deleting an AS Policy
- Batch Managing AS Policies
- AS Policy Execution Logs
- Scaling Action Logs
- Quotas
- Notifications
- Lifecycle Hooks
- Tags
- API Version Query
- Application Examples
- Permissions Policies and Supported Actions
- Appendix
- Change History
- SDK Reference
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FAQs
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General
- What Are Restrictions on Using AS?
- Must I Use AS Together With ELB and Cloud Eye?
- Is AS Billed?
- Will an Abrupt Change in Monitoring Metric Values Trigger an Unnecessary Scaling Action?
- How Many AS Policies and AS Configurations Can I Create and Use?
- Can AS Automatically Scale Up or Down vCPUs, Memory, and Bandwidth of ECSs?
- What Is an AS Quota?
- How Do I Fix the Error "The key pair does not exist" When I Connect to an Instance?
- What Types of EIP and Shared Bandwidths Can Be Adjusted by AS?
- What Types of ECS and HECS Instances Can Be Scaled by AS?
- If the OS of an ECS Instance in an AS Group Is Upgraded, Can AS Automatically Add Instances with the Newest OS During the Next Scale-out Action?
- Can AS Add Yearly/Monthly ECS Instances When It Scales Out an AS Group?
- Can AS Increase Bandwidths as Required?
- AS Group
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AS Policy
- How Many AS Policies Can I Enable?
- What Are the Conditions to Trigger an Alarm-based AS Policy?
- What Is a Cooldown Period and Why Is It Required?
- Can AS Scale Capacity Based on Custom Monitoring by Cloud Eye?
- What Monitoring Metrics for an AS Group Will Be Affected If VM Tools Are Not Installed on the Instances in the Group?
- What Can I Do If an AS Policy Fails to Be Enabled?
- How Do I Install the Agent on Instances in an AS Group to Use Agent Monitoring Metrics?
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Instance
- How Do I Prevent Instances Manually Added to an AS Group from Being Automatically Removed?
- When an Instance Is Removed from an AS Group and Deleted, Is the Application Data Saved?
- Can I Add Yearly/Monthly ECS Instances to an AS Group?
- Can AS Automatically Delete Instances Added Based on an AS Policy When They Are Not Required?
- What Is the Expected Number of Instances?
- How Do I Delete an ECS Instance Created in a Scaling Action?
- Will ECS Instances Be Deleted If They Become Unhealthy?
- How Do I Handle Unhealthy Instances in an AS Group?
- Why Instances in an AS Group Keep Failing Health Checks and Getting Deleted and Recreated?
- How Do I Prevent Instances from Being Automatically Removed from an AS Group?
- Why Is an Instance that Was Removed from an AS Group and Deleted Still Displayed in the ECS List?
- Do I Need to Bind an EIP to an Instance Before I Manually Add the Instance to an AS Group?
- Can I Apply the Configurations of an Existing Instance in an AS Group to Instances to Be Added in the Future?
- Will the System Bind a New EIP or an Existing One a Newly Added ECS Instance?
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Others
- How Can I Automatically Deploy My Application on an Instance?
- How Does Cloud-Init Affect the AS Service?
- Why Can't I Use a Key File to Log In to an ECS?
- Do I Need to Configure an EIP in an AS Configuration When a Load Balancer Has Been Enabled for an AS Group?
- How Do I Enable Automatic Initialization of EVS Disks on Instances that Have Been Added to an AS Group During Scaling Actions?
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General
- Videos
Show all
What Is a Cooldown Period and Why Is It Required?
A cooldown period specifies how long any alarm-triggered scaling action will be disallowed after a previous scaling action is complete. This cooldown period does not work for scheduled or periodic scaling actions.
Before an instance is put into use after it is added to the AS group, it takes 2 to 3 minutes to execute the configuration script to install and configure applications. The time varies depending on many factors, such as the instance specifications and startup scripts. If an instance is put into use without cooldown, the system will keep adding instances until the load decreases. As the new instances take over services, the system will detect that the load is too low and start removing instances from the AS group. A cooldown prevents the AS group from repeatedly triggering unnecessary scaling actions.
For example:
When a traffic peak occurs, an alarm policy is triggered and AS automatically adds an instance to the AS group to help handle the increased load. However, it takes time for the instance to start. After the instance is started, it takes time to receive requests from ELB. During this period, alarms may continue to be triggered and instances may continue to be added. If you set a cooldown time, after an instance is started, AS stops adding new instances in response to the alarms until the specified period of time (300 seconds by default) passes. That way the newly started instance has time to start processing application traffic. If an alarm is triggered again after the cooldown period elapses, AS starts another instance and the cooldown period starts up again.
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