AWS autoscaling documentation change
Summary
Updated documentation for Amazon EC2 Auto Scaling instance refresh feature. Added details about two refresh strategies (rolling and replace root volume), requirements for root volume replacement, skip matching functionality, and compatibility restrictions. Updated terminology from 'Auto Scaling group' to 'Amazon EC2 Auto Scaling group' throughout.
Security assessment
The changes introduce operational improvements (new refresh strategies) and documentation clarifications without addressing any specific security vulnerabilities. The replace root volume strategy preserves network interfaces and data volumes, but this is an availability feature rather than a security fix. No security advisories, vulnerabilities, or security-specific configurations are mentioned.
Diff
diff --git a/autoscaling/ec2/userguide/instance-refresh-overview.md b/autoscaling/ec2/userguide/instance-refresh-overview.md index 471508738..3bc1b2e26 100644 --- a//autoscaling/ec2/userguide/instance-refresh-overview.md +++ b//autoscaling/ec2/userguide/instance-refresh-overview.md @@ -7 +7 @@ How it worksCore conceptsHealth check grace periodInstance type compatibilityLim -# How an instance refresh works in an Auto Scaling group +# How an instance refresh works in an Amazon EC2 Auto Scaling group @@ -28 +28 @@ This topic describes how an instance refresh works and introduces the key concep -To refresh instances in an Auto Scaling group, you can define a new configuration that contains the latest version of your application and any other updates you want to make. Then, start an instance refresh to replace existing instances with new ones based on that configuration. +To refresh instances in an Amazon EC2 Auto Scaling group, you can define a new configuration that contains the latest version of your application and any other updates you want to make. @@ -30 +30 @@ To refresh instances in an Auto Scaling group, you can define a new configuratio -To perform an instance refresh: +Instance refresh supports two strategies for updating instances: @@ -32 +32,29 @@ To perform an instance refresh: - 1. Create a new launch template or update the existing template with the desired configuration changes, such as a new Amazon Machine Image (AMI). For more information, see [Create a launch template for an Auto Scaling group](./create-launch-template.html). + * **Rolling strategy (default)** — Terminates instances and launches new ones in batches according to your preferences. This ensures that your Auto Scaling group maintains its desired capacity and availability throughout the update process. + + * **Replace root volume strategy** — Updates instances by replacing only the root volume without terminating the instance. This preserves instance network interfaces, non-root EBS volumes, and instance store data. + + + + +Requirements for replace root volume strategy: + + * Your Auto Scaling group must use a mixed instances policy + + * All overrides in the mixed instances policy must specify an `ImageId` + + * AMIs must contain only a single root volume + + * All instances must match the group's launch template configuration + + * You must start the instance refresh with a desired configuration + + + + +When skip matching is enabled, Auto Scaling compares each instance's current AMI ID against the AMI IDs in your desired configuration. It only replaces instances where the AMI IDs don't match, allowing you to skip instances that are already updated. + +### Perform an instance refresh + +Start an instance refresh to replace existing instances with new ones based on that configuration. + + 1. Create a new launch template or update the existing template with the desired configuration changes, such as a new Amazon Machine Image (AMI). For more information, see [Create a launch template for an Amazon EC2 Auto Scaling group](./create-launch-template.html). @@ -63 +91 @@ When the instance refresh has started, Amazon EC2 Auto Scaling will: - * Automatically update the Auto Scaling group settings with the new configuration changes after the instance refresh succeeds. + * Automatically update the Amazon EC2 Auto Scaling group settings with the new configuration changes after the instance refresh succeeds. @@ -78 +106 @@ The minimum and maximum healthy percentages for an instance refresh only need to -Similarly, you only need to specify the instance warmup period for an instance refresh if you have not enabled the default warmup, or if you need to override the default. For more information, see [Set the default instance warmup for an Auto Scaling group](./ec2-auto-scaling-default-instance-warmup.html). +Similarly, you only need to specify the instance warmup period for an instance refresh if you have not enabled the default warmup, or if you need to override the default. For more information, see [Set the default instance warmup for an Amazon EC2 Auto Scaling group](./ec2-auto-scaling-default-instance-warmup.html). @@ -94 +122 @@ An instance refresh can replace instances one at a time, several at a time, or a -The _maximum healthy percentage_ is the percentage of the desired capacity that your Auto Scaling group can increase to when replacing instances. The difference between the minimum and maximum cannot be greater than 100. A larger range increases the number of instances that can be replaced at the same time. +The _maximum healthy percentage_ is the percentage of the desired capacity that your Amazon EC2 Auto Scaling group can increase to when replacing instances. The difference between the minimum and maximum cannot be greater than 100. A larger range increases the number of instances that can be replaced at the same time. @@ -101 +129 @@ The _instance warmup_ is the time period from when a new instance's state change -The instance warmup works the same way as the default instance warmup. Therefore, the same scaling considerations apply. For more information, see [Set the default instance warmup for an Auto Scaling group](./ec2-auto-scaling-default-instance-warmup.html). +The instance warmup works the same way as the default instance warmup. Therefore, the same scaling considerations apply. For more information, see [Set the default instance warmup for an Amazon EC2 Auto Scaling group](./ec2-auto-scaling-default-instance-warmup.html). @@ -106 +134 @@ The instance warmup works the same way as the default instance warmup. Therefore -The _desired configuration_ is the new configuration that you want Amazon EC2 Auto Scaling to deploy across your Auto Scaling group. For example, you can specify a new launch template and new instance types for your instances. During an instance refresh, Amazon EC2 Auto Scaling updates the Auto Scaling group to the desired configuration. If a scale-out event occurs during an instance refresh, Amazon EC2 Auto Scaling launches new instances with the desired configuration instead of the group's current settings. After the instance refresh succeeds, Amazon EC2 Auto Scaling updates the Auto Scaling group settings to reflect the new desired configuration that you specified as part of the instance refresh. +The _desired configuration_ is the new configuration that you want Amazon EC2 Auto Scaling to deploy across your Amazon EC2 Auto Scaling group. For example, you can specify a new launch template and new instance types for your instances. During an instance refresh, Amazon EC2 Auto Scaling updates the Amazon EC2 Auto Scaling group to the desired configuration. If a scale-out event occurs during an instance refresh, Amazon EC2 Auto Scaling launches new instances with the desired configuration instead of the group's current settings. After the instance refresh succeeds, Amazon EC2 Auto Scaling updates the Amazon EC2 Auto Scaling group settings to reflect the new desired configuration that you specified as part of the instance refresh. @@ -111 +139 @@ The _desired configuration_ is the new configuration that you want Amazon EC2 Au -Skip matching tells Amazon EC2 Auto Scaling to ignore instances that already have your latest updates. This way, you don't replace more instances than you need to. This is helpful when you want to make sure your Auto Scaling group uses a particular version of your launch template and only replaces those instances that use a different version. +Skip matching tells Amazon EC2 Auto Scaling to ignore instances that already have your latest updates. This way, you don't replace more instances than you need to. This is helpful when you want to make sure your Amazon EC2 Auto Scaling group uses a particular version of your launch template and only replaces those instances that use a different version. @@ -122 +150 @@ To learn more about all of the default settings you can configure when starting -Amazon EC2 Auto Scaling determines whether an instance is healthy based on the status of the health checks that your Auto Scaling group uses. For more information, see [Health checks for instances in an Auto Scaling group](./ec2-auto-scaling-health-checks.html). +Amazon EC2 Auto Scaling determines whether an instance is healthy based on the status of the health checks that your Amazon EC2 Auto Scaling group uses. For more information, see [Health checks for instances in an Amazon EC2 Auto Scaling group](./ec2-auto-scaling-health-checks.html). @@ -124 +152 @@ Amazon EC2 Auto Scaling determines whether an instance is healthy based on the s -To make sure that these health checks start as soon as possible, don't set the group's health check grace period too high, but high enough for your Elastic Load Balancing health checks to determine whether a target is available to handle requests. For more information, see [Set the health check grace period for an Auto Scaling group](./health-check-grace-period.html). +To make sure that these health checks start as soon as possible, don't set the group's health check grace period too high, but high enough for your ELB health checks to determine whether a target is available to handle requests. For more information, see [Set the health check grace period for an Amazon EC2 Auto Scaling group](./health-check-grace-period.html). @@ -141 +169 @@ For information about how compatibility is determined, see [Compatibility for ch - * **Difference in behavior specific to weighted groups** — If a mixed instances group is configured with an instance weight that is larger than or equal to the group's desired capacity, Amazon EC2 Auto Scaling might replace all `InService` instances at once. To avoid this situation, follow the recommendation in the [Configure an Auto Scaling group to use instance weights](./ec2-auto-scaling-mixed-instances-groups-instance-weighting.html) topic. Specify a desired capacity that is larger than your largest weight when you use weights with your Auto Scaling group. + * **Difference in behavior specific to weighted groups** — If a mixed instances group is configured with an instance weight that is larger than or equal to the group's desired capacity, Amazon EC2 Auto Scaling might replace all `InService` instances at once. To avoid this situation, follow the recommendation in the [Configure an Amazon EC2 Auto Scaling group to use instance weights](./ec2-auto-scaling-mixed-instances-groups-instance-weighting.html) topic. Specify a desired capacity that is larger than your largest weight when you use weights with your Amazon EC2 Auto Scaling group. @@ -147 +175,3 @@ For information about how compatibility is determined, see [Compatibility for ch - * **Update restriction** — If you attempt to update an Auto Scaling group's launch template, launch configuration, or mixed instances policy while an instance refresh with a desired configuration is active, the request will fail with the following validation error: `An active instance refresh with a desired configuration exists. All configuration options derived from the desired configuration are not available for update while the instance refresh is active.` + * **Update restriction** — If you attempt to update an Amazon EC2 Auto Scaling group's launch template, launch configuration, or mixed instances policy while an instance refresh with a desired configuration is active, the request will fail with the following validation error: `An active instance refresh with a desired configuration exists. All configuration options derived from the desired configuration are not available for update while the instance refresh is active.` + + * **Attribute-based instance selection** — If your Amazon EC2 Auto Scaling group uses attribute-based instance selection (specifying `InstanceRequirements` in a mixed instances policy), the following instance refresh parameters aren't supported: @@ -149 +179 @@ For information about how compatibility is determined, see [Compatibility for ch - * **Attribute-based instance selection** — If your Auto Scaling group uses attribute-based instance selection (specifying `InstanceRequirements` in a mixed instances policy), the following instance refresh parameters aren't supported: + * **SkipMatching** \- An instance refresh will fail if you start it with the `SkipMatching` parameter in an Amazon EC2 Auto Scaling group that has `InstanceRequirements` configured. @@ -151 +181 @@ For information about how compatibility is determined, see [Compatibility for ch - * **SkipMatching** \- An instance refresh will fail if you start it with the `SkipMatching` parameter in an Auto Scaling group that has `InstanceRequirements` configured. + * **DesiredConfiguration** \- An instance refresh will fail if you start it with the `DesiredConfiguration` parameter in an Amazon EC2 Auto Scaling group that has `InstanceRequirements` configured. @@ -153 +183 @@ For information about how compatibility is determined, see [Compatibility for ch - * **DesiredConfiguration** \- An instance refresh will fail if you start it with the `DesiredConfiguration` parameter in an Auto Scaling group that has `InstanceRequirements` configured. +If you need to perform an instance refresh on an Amazon EC2 Auto Scaling group with attribute-based instance selection, start the instance refresh without these parameters. @@ -155 +185 @@ For information about how compatibility is determined, see [Compatibility for ch -If you need to perform an instance refresh on an Auto Scaling group with attribute-based instance selection, start the instance refresh without these parameters. + * Root volume replacement doesn’t support Elastic Load Balancing.