When you create pay-as-you-go instances during peak demand, creation may fail due to insufficient inventory. Elasticity Assurance (EA) provides capacity assurance for pay-as-you-go instances by reserving resources in a dedicated private pool.
Use cases
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Scenario |
Periodic resource demand |
Occasional resource demand |
Peak resource demand |
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Diagram |
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Description |
Suitable for predictable, periodic resource peaks. Ensures tasks start on time and prevents resource waste during off-peak periods. |
Reserves resources for unexpected events or traffic spikes to ensure rapid business response and high availability. |
During periods of high resource contention across the cloud, such as major sales promotions or holidays, you can reserve resources for your core services in advance to prevent business disruptions. |
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Example |
Month-end financial reconciliation, weekend batch rendering, and daily scheduled data analytics. |
Responding to sudden trending events, scaling out applications, and performing disaster recovery for online services. |
Live video streaming, e-commerce promotions, new online game server launches, and flash sales for tickets. |
Key concepts
When you purchase an Elasticity Assurance, the system reserves resources that match the specified instance type and quantity in a designated zone. These resources form a private pool.
A public pool is a resource pool shared by all users. If you do not specify a private pool when you create an instance, the system allocates resources from the public pool by default.
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Feature |
Dedicated private pool |
Open private pool |
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Access policy |
Strict binding (Strong guarantee): Uses only the dedicated private pool. If the capacity is insufficient, instance creation fails. |
Priority + Fallback: Prioritizes the open private pool. If the capacity is insufficient, the system falls back to the public pool. |
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Resource isolation |
Reserved for specific services or scenarios that require strong isolation. |
Can be used as a general capacity pool shared by multiple business scenarios. |
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Usage |
When you create an instance, use the Targeted mode to specify a dedicated private pool. |
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Elasticity Assurance - Time-based: Reserves resources for preset time slots, such as 18:00 to 24:00 daily, within a specified period, such as 30 days.
Elasticity Assurance: Reserves resources continuously for a specified period, such as three months.
Procedure
Workflow
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Purchase an Elasticity Assurance: Purchase an Elasticity Assurance to obtain a private pool.
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Create an ECS instance: When you create the instance, specify the private pool associated with the purchased Elasticity Assurance.
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Verify and manage: View the private pool usage and associated instances.
Elasticity Assurance - Time-based
Step 1: Purchase assurance
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Go to the ECS console - Elasticity Assurance page.
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Click Create Elasticity Assurance.
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The interval between the Start time and Expiration Time must be at least 7 days and at most 365 days.
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Repeat Rule: You can configure up to 10 rules.
You can set the assurance period based on a daily, weekly, or monthly recurrence. The minimum duration for a Time is 4 hours, and the total assured duration must be at least 10% of the entire period.
Hover over Coverage period (UTC) preview to view the details of the assurance period.
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Private Pool Type:
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Open: Creates an open private pool.
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Targeted: Creates a dedicated private pool reserved for a specific scenario or service.
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Select I have read and understood the notes. and click Buy Now.
Return to the ECS console - Elasticity Assurance page. When the status is Resource Locked or Active, the purchase is successful.
Step 2: Create instances
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Go to the ECS console - Elasticity Assurance page.
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On the Create Resource Reservation page, find the target Elasticity Assurance and click Purchase Instance in the Operation column.
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Set Type of payment to Pay-as-you-go. For more information about how to configure other parameters, see Create a custom instance.
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At the bottom of the page, expand Advanced Options and select a Private Pool Type.
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Open: The system prioritizes using an open private pool. If the capacity is insufficient, the system falls back to the public pool.
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Do Not Use: Do not use a private pool. Resources are allocated only from the public pool.
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Targeted: Specify a matching open or dedicated private pool.
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Click Confirm Order.
Step 3: View assurance details
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Go to the ECS console - Elasticity Assurance page.
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On the Elasticity Assurance page, click the ID of an Elasticity Assurance to go to its details page. On this page, you can view information such as the capacity usage of the private pool.
In the Associated Instances section, you can view the instances created using this Elasticity Assurance.
Elasticity Assurance
Step 1: Purchase assurance
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Go to the ECS console - Resource Center and choose .
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On the Resource Reservations tab, click Create Resource Reservation to go to the configuration page.
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Resource Settings: Select the Region/Zone, Resource Type, and Reserved Quantity.
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Resource Reservation Settings:
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Reservation Type: Select Immediate or Scheduled Elasticity Assurance.
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Duration of purchase: You can purchase the service on a monthly or yearly basis for a period of 1 month to 5 years.
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Private Pool Information:
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Open: Creates an open private pool.
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Targeted: Creates a dedicated private pool reserved for a specific scenario or service.
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Recommended Plans:
The system recommends plans based on inventory priority, multi-zone disaster recovery, and performance priority. Resources are reserved based on the plan that you select.
Select your desired plan.
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Click Next: Preview and verify the configuration.
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Read the Notes, select I have read and understood the preceding notes, and click Create.
Return to the list page. When the status changes to Active, the purchase is successful.
Step 2: Create instances
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Go to the ECS console - Resource Center and choose .
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On the Resource Reservations page, find the target resource reservation and click Purchase Instance in the Actions column.
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Set Type of payment to Subscription. For more information about how to configure other parameters, see Create a custom instance.
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In the Advanced Settings (Optional) section, select a Private Pool Type.
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Open: The system prioritizes using an open private pool. If the capacity is insufficient, the system falls back to the public pool.
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None: Do not use any private pool. Resources are allocated only from the public pool.
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Targeted: Specify an open or dedicated private pool.
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Step 3: View assurance details
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Go to the ECS console - Resource Center.
In the upper-left corner of the page, select a region and resource group.
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In the left-side navigation pane of Resource Center, choose .
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On the Resource Reservations tab, filter by Reservation Type and select Elasticity Assurance.
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In the filtered Elasticity Assurance list, click the ID of an Elasticity Assurance to go to its details page. On this page, you can view information such as the capacity usage of the private pool.
In the Associated Instances section, you can view the instances created using this Elasticity Assurance.
API
Step 1: Create and purchase assurance
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Call the CreateElasticityAssurance operation to create an Elasticity Assurance or an Elasticity Assurance - Time-based.
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Call the PurchaseElasticityAssurance operation to purchase a prepared and inactive Elasticity Assurance.
Step 2: Create an instance
Call the RunInstances operation to create an instance.
Specify the private pool type by using PrivatePoolOptions.MatchCriteria. If you set the private pool type to Targeted mode (Target), you must use PrivatePoolOptions.Id to specify the ID of the target private pool.
Step 3: View and modify assurance
Query
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Call the DescribeElasticityAssurances operation to query the details of Elasticity Assurances.
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Call the DescribeElasticityAssuranceInstances operation to query the list of instances that are matched by an Elasticity Assurance.
Modify
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Call the ModifyElasticityAssurance operation to modify information about an Elasticity Assurance, such as its name, description, and capacity.
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Call the ModifyInstanceAttachmentAttributes operation to modify the private pool matching mode for an instance.
Use cases and recommended strategies
Scenario 1: Core services - Guarantee resource certainty
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Applicable services: Core applications such as e-commerce promotions, game server launches, and financial settlements.
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Recommended strategy: Purchase a dedicated private pool and use Targeted mode when you create instances.
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Result: As long as the private pool has available capacity, instance creation succeeds. This avoids the risk of creation failures due to insufficient public resources.
Scenario 2: High-priority services - Balance assurance and elasticity
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Applicable services: Scenarios such as data analytics, batch computing, and routine scale-outs for online services, where you want to prioritize assurance but also use public resources as a supplement.
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Recommended strategy: Purchase an open private pool and use Open mode when you create instances.
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Result: The reserved capacity is used first. If the reserved capacity is exhausted, the system falls back to the public pool.
Scenario 3: Non-core or dev/test - Prioritize cost
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Applicable services: Development and testing environments, or non-core services that can tolerate occasional creation failures.
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Recommended strategy: When you create instances, select None for the private pool option.
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Result: The public pool is used, but instance creation may fail due to inventory fluctuations in the public pool.
Billing
The cost of an Elasticity Assurance consists of two parts:
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Assurance fee (upfront): A one-time service fee that you pay when you purchase the Elasticity Assurance.
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Instance fee (pay-as-you-go): Pay-as-you-go instances that are successfully created from the private pool are billed at the standard price.
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Assurance type |
Elasticity Assurance - Time-based |
Elasticity Assurance |
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Diagram |
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Assurance fee formula |
The assured duration is the total duration of non-contiguous time slots. |
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Total fee |
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Instance fee deduction order: For pay-as-you-go instances created from an Elasticity Assurance, their hourly bills are deducted from matching savings benefits in the following order:
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Zonal Reserved Instances are not supported.
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If no savings benefits apply, you are billed at the standard pay-as-you-go price.
Limitations
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Availability: Elasticity Assurance is available only in specific regions, zones, and for specific instance types. The options shown on the purchase page in the console are final.
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No modifications or early releases: After you purchase an Elasticity Assurance, you cannot change its capacity, cancel the order, or release it ahead of schedule. It expires automatically.
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Attribute matching: When you create an instance, the selected region, zone, and instance type must exactly match the attributes of the Elasticity Assurance.
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Scope of assurance: The assurance guarantees only the capacity availability of the ECS instance type. It does not guarantee the inventory of associated resources, such as cloud disks, public IP addresses, or elastic network interfaces (ENIs).
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Effect of instance operations: If you resize an instance created using an Elasticity Assurance, the instance is disassociated from the private pool and no longer benefits from the resource availability assurance.
Production recommendations
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Integrate with Auto Scaling: Use Elasticity Assurance with Auto Scaling (ESS) to automate resource scheduling.
When you create or modify a scaling group, set the Resource Pool Policy to prioritize using the private pool capacity of the Elasticity Assurance.
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Resource Pool Policy options:
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Prioritize Private Pool: Prioritizes the use of the specified private pool. If the private pool has insufficient capacity, the system automatically uses an open private pool or the public pool.
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Private Pool Only: The instances must use the capacity from a private pool. Otherwise, instance creation will fail.
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Configuration steps:
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Log on to the Auto Scaling console.
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Create or modify a scaling group.
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In the Advance Settings section of the scaling configuration, select a resource pool policy and specify an Elasticity Assurance private pool.
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Monitoring and alerting: Use CloudMonitor to create alert rules for key metrics to monitor capacity usage. For example, you can trigger an alert when the available capacity drops below 20% of the total capacity:
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Set Product to ECS Private Pool.
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Set Metric to Instance Number Usage, Warning to Warning, and the threshold to 20%.
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Related documents
Comparison between Elasticity Assurance and Capacity Reservation
FAQ
Q: Why isn't the capacity of my Elasticity Assurance updated immediately after I release an instance?
A: Releasing an instance is not instantaneous. To prevent creation failures due to this delay, avoid creating and releasing instances in rapid succession.
Q: Can a single Elasticity Assurance be used across multiple zones?
A: No. If you require assurance across multiple zones, you must create a separate Elasticity Assurance in each zone.
Q: Does Elasticity Assurance support changing instance types?
A: No. The instance type bound to an Elasticity Assurance cannot be changed after purchase.
Q: How do I view the remaining capacity of a private pool?
A: On the Elasticity Assurance list page, click the ID of an Elasticity Assurance. You can then view the capacity usage in the Resource Details section.
Q: What is the purpose of tags for an Elasticity Assurance?
A: When you create an instance, the system can match an instance to an open private pool based on tags.
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Tag: If you add tags to an instance that match the tags of an open private pool, the instance is automatically matched with that pool.
After an Elasticity Assurance takes effect, it always uses the tags that were specified at the time of purchase for private pool matching.
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Tag: If you do not add tags to the instance, the system automatically matches the instance with an available open private pool.