• Auto Scaling

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  4. Basic Concepts

Basic Concepts

AS Introduction

AS is a service that automatically adjusts resources based on your service requirements and configured AS policies. Users can specify AS configurations and policies based on service requirements. These configurations and policies free you from having to repeatedly adjust resources to keep up with service changes and demand spikes, thereby reducing resources required and manpower costs.

AS Development Mode

API Calling

Public cloud services provide RESTful APIs.

Representational State Transfer (REST) allocates Uniform Resource Identifiers (URIs) to dispersed resources so that resources can be located. Applications on clients use Uniform Resource Locators (URLs) to obtain resources.

The URL is in the following format: https://Endpoint/uri

Table 1 lists the parameters in a URL.

Table 1 Parameter description

Parameter

Description

Endpoint

Specifies the URL that is the entry point for a web service. Obtain the value from Regions and Endpoints.

URI

Specifies the API access path for performing a specified operation. Obtain the value from the URI of the API, for example, v3/auth/tokens.

Basic Concepts

AS Group

An AS group consists of a collection of instances that apply to the same scenario. It is the basis for enabling or disabling AS policies and performing scaling actions.

AS Configuration

An AS configuration is an Elastic Cloud Server (ECS) instance template in an AS group, specifying specifications of the ECS to be added, including the ECS type, vCPU, memory, image, disk, and login mode.

AS Policy

An AS policy specifies a condition for triggering a scaling action.

AS supports the following policies:

Alarm: AS automatically increases or decreases the number of instances in an AS group or sets the number of instances to a specified value if Cloud Eye generates an alarm for a configured metric, such as CPU usage.

Periodic: AS increases or decreases the number of instances in an AS group or sets the number of instances to a specified value at a configured interval, such as one day, one week, or month.

Scheduled: AS automatically increases or decreases the number of instances in an AS group or sets the number of instances to a specified value at a specified time.

Instance

An instance is an ECS in an AS group.

Scaling Action

A scaling action adds or removes instances to or from an AS group so that the number of instances in the AS group is the same as the expected number for proper service running.

When the number of instances in an AS group is not the same as expected, a scaling action is triggered. Specifically, when the scaling condition is met or you manually change the expected number of instances, a scaling action is triggered.