When your application needs more compute capacity, add Elastic Compute Service (ECS) instances to scale it out. Enterprise Distributed Application Service (EDAS) supports three scale-out methods: selecting idle instances from the cluster, purchasing new instances based on an existing instance's specs, or purchasing instances from a launch template.
Choose a scale-out method
| Method | Best for | Prerequisites | Billing impact |
|---|---|---|---|
| Select from cluster | Quick scaling with available idle instances | Idle instances in the cluster | None (existing instances) |
| Purchase based on existing specs | Replicating a known-good instance configuration | At least one instance in the cluster to use as a template | New ECS instances billed per standard ECS and EDAS pricing |
| Purchase from a launch template | Standardized, repeatable provisioning | A launch template created in the ECS console, in the same VPC as the application | New ECS instances billed per standard ECS and EDAS pricing |
How added instances behave
The application's current state determines what happens to newly added instances:
| Application state before scale-out | Result |
|---|---|
| Deployed and running | EDAS automatically deploys and starts the application on the added instances. |
| Deployed but stopped | EDAS automatically deploys and starts the application on the added instances. |
| Not yet deployed | The application is not deployed. The added instances remain stopped. |
Prerequisites
Before you begin, make sure that you have:
An EDAS application deployed in an ECS cluster
The required permissions to manage the application and its instances
(For the launch template method) A launch template created in the ECS console, in the same Virtual Private Cloud (VPC) as your application
Start a scale-out
All three methods begin from the same entry point in the EDAS console.
Log on to the EDAS console.
In the left-side navigation pane, choose Application Management > Applications.
In the top navigation bar, select the region. On the Applications page, select a microservices namespace from the Microservice Namespace drop-down list.
Click the application name.
On the application details page, click Scale Out in the upper-right corner.
In the Add Instance dialog box, set Target Group, then choose a Scale-out Method.
Follow the steps for your chosen method.
Select from cluster
Use this method to assign idle instances that already exist in the cluster to the application.
For Scale-out Method, select Select from Clusters Deployed with the Application.
In the instance list, select the idle instances to add, then click Scale Out.
After the message The application is scaled out appears, verify the scale-out.
Purchase based on existing instance specs
Use this method to purchase new ECS instances with the same configuration -- instance type, disks, network, user data, and tags -- as an existing instance in the cluster.
For Scale-out Method, select Purchase Based on Existing Instance Specifications. All instances in the cluster are listed.
Select the instance to use as the specification template, set the Recycling Mode, and click Next.
In the Purchase Details step, set Quantity and Password, select Elastic Compute Service Terms of Service Terms of Service for Images, and click Next.
In the Confirm step, review the instance details and click Confirm. The message Automatic purchasing is triggered. Check the real-time information in the application change process appears.
- This method involves two sequential change processes: EDAS first purchases the ECS instances, then automatically adds them to the application.
- The scale-out starts approximately three minutes after you submit the request. The interval between the two change processes is approximately 10 seconds.
- Standard ECS and EDAS billing rules apply. The scale-out operation itself is not charged.
- By default, EDAS uses the AccessKey pair that you specified at logon to access the ECS instances.
Purchase from a launch template
Use this method to purchase new ECS instances from an instance launch template that you created in the ECS console. For details on creating a template, see Create a launch template.
The launch template and your application must be in the same VPC. If they are in different VPCs, the template does not appear in the selection list.
For Scale-out Method, select Purchase Based on Instance Launch Template.
Select the template source:
Use Bound Template: Use a launch template already bound to the application instance group. For details, see Associate a launch template with an application instance group.
Use Specified Template: Select a launch template from the ECS console and choose a version.
Set the Recycling Mode and click Next.
In the Purchase Details step, set Quantity, select Elastic Compute Service Terms of Service Terms of Service for Images, and click Next.
In the Confirm step, review the purchase quantity and template details, then click Confirm. The message Automatic purchasing is triggered. Check the real-time information in the application change process appears.
Verify the scale-out
On the application details page, click the Instance Information tab. Check the status of the added instances. A status of Normal indicates that the scale-out succeeded.
What's next
To automatically adjust the number of ECS instances based on metrics and schedules, configure auto scaling. See Perform auto scaling on applications in ECS clusters.