It’s critical to understand how to manage your AWS resources effectively – and understanding service quotas and throttling opens up a whole new dimension to optimized resource usage. These features enable you to configure the use of your resources to best suit your needs, ensuring that your applications maintain peak performance and stability.
Understanding Service Quotas
Service quotas (also known as limits) are the maximum number of resources that you can create in your AWS account in a given region for a specific AWS service. These quotas are imposed to prevent accidental over-provisioning which can lead to unexpectedly high bills, as well as to protect the shared resources in each region. For example, the number of Amazon EC2 instances that you can run, or the number of AWS Lambda functions you can create, are both controlled by service quotas.
By default, AWS sets these quotas at levels that are appropriate for most users. However, in some cases, you might need to request a quota increase. You can do this via the AWS Service Quotas console, CLI, or API.
Understanding Throttling
While service quotas govern your maximum resource usage, throttling limits the rate at which you can call or request a particular AWS service. Throttling ensures that services aren’t overwhelmed with too many requests at once, avoiding potential latency or disruption issues.
Let’s take Amazon EC2 API requests as an example: by default, the “DescribeInstances” API call is throttled at a rate of about 100 requests per second (rps). If your application needs to make more calls than this, it will receive “Throttle Errors” from the EC2 service.
Configuring Service Quotas for a Standby Environment Workload
Usually, your standby environment should have similar quotas as your production environment to handle sudden shifts in workload. Here’s how to check and configure the quotas:
- Navigate to the Service Quotas console in your AWS Management Console.
- In the navigation pane, choose the service you want to configure (e.g., Amazon EC2).
- In the details pane, you’ll see various quota types. Choose the one you want to adjust (e.g., Running On-Demand Standard instances).
- Click ‘Request quota increase’ and follow the prompts.
Note: It may take some time for AWS to process a quota increase request, so it’s always good to plan ahead.
Managing API Request Throttling
The strategy to handle API request throttling mainly revolves around implementing retry and exponential backoff algorithms. When these error codes are received, applications should ideally wait and retry the failed request. Libraries such as the AWS SDK for Java and .NET provide this feature.
// Example in Java using AWS SDK
try {
DescribeInstanceStatusRequest request = new DescribeInstanceStatusRequest();
DescribeInstanceStatusResult response = ec2.describeInstanceStatus(request);
for(InstanceStatus status : response.getInstanceStatuses()) {
System.out.printf(
"Retrieved instance %s in state %s",
status.getInstanceId(),
status.getInstanceState());
}
} catch (AmazonServiceException e) {
if (ErrorCode.fromValue(e.getErrorCode()) == ErrorCode.Throttling) {
tagExpressionRetryStrategy.retry();
} else {
throw e;
}
}
In this example, the ‘tagExpressionRetryStrategy.retry()’ is a method that will implement a delay before retrying thus avoiding continuous Throttling errors.
Conclusion
Understanding and managing service quotas and throttling is a crucial part of designing reliable, efficient, and cost-effective AWS solutions. As Solutions Architects, we should aim to design systems that fit within service quotas, and implement graceful handling of throttling scenarios. This ensures that our systems maintain their performance, while also keeping costs down.
Practice Test
True/False: Each AWS service has a default quota or throttle limit that restricts the usage of the service.
- True
- False
Answer: True
Explanation: Each AWS service is subject to service quotas (also referred to as limits) that restrict the usage of the service to protect against unexpected usage spikes.
True/False: You can increase service quotas for any AWS service as per your requirements without reaching out to AWS Support.
- True
- False
Answer: False
Explanation: Some service quotas can be increased by submitting a request to AWS support, while others are fixed and cannot be changed.
Select the correct method to check the service quota of a specific AWS service:
- A. Using AWS Management Console
- B. Using AWS CLI
- C. AWS SDKs
- D. All of the above
Answer: D. All of the above
Explanation: AWS provides various ways to check the service quotas including AWS Management Console, AWS CLI, or AWS SDKs.
Can an increased service quota be decreased back to the default limit?
- A. Yes
- B. No
Answer: B. No
Explanation: Once a service quota has been increased, it can not be reduced back to the default limit.
AWS Trusted Advisor can be used to ____.
- A. View current service quota increase requests
- B. Monitor service quota utilization
- C. Submit requests to increase service quotas
- D. All of the above
Answer: B. Monitor service quota utilization
Explanation: AWS Trusted Advisor provides real-time guidance to provision resources following AWS best practices and also helps monitor service quota utilization.
What happens when a service quota is exceeded in AWS?
- A. Extra charges apply
- B. The service operation may be throttled
- C. AWS automatically increases the quota
- D. None of the above
Answer: B. The service operation may be throttled
Explanation: If a service’s quota is exceeded, the service operation may get throttled leading to decreased performance or errors.
Service quotas apply to AWS services used in _____.
- A. Production environments only
- B. Standby environments only
- C. Both production and standby environments
Answer: C. Both production and standby environments
Explanation: Service quotas apply to all AWS service usage, regardless of whether you’re using it in a production, standby, or testing environment.
True/False: Each AWS region has distinct service quotas for AWS services.
- True
- False
Answer: True
Explanation: Service quotas are often defined per region, and usage in one region does not impact the availability of resources in another region.
Can service quotas be configured to automatically increase as the workload increases?
- A. Yes
- B. No
Answer: B. No
Explanation: Service quotas cannot be configured to automatically increase in response to workload increases. They must be manually adjusted by submitting a request to AWS Support.
In AWS, throttling refers to _____.
- A. The rate at which AWS reads from disks
- B. AWS slowing the Internet connection
- C. AWS limiting an application’s usage of an AWS service by returning an error message
- D. None of the above
Answer: C. AWS limiting an application’s usage of an AWS service by returning an error message
Explanation: In AWS, throttling refers to the intentional slowing or limiting of an application’s usage of an AWS service by returning an error message when the application exceeds a service quota.
Interview Questions
What is service quotas in AWS?
Service quotas are the maximum values for resources, actions, and items in your AWS account. Service quotas also determine the maximum throughput a service can handle.
What is the use of AWS Service Quotas?
AWS Service Quotas is a service that allows you to view and manage your quotas for AWS services from a central location. It gives a unified view of service usage and quotas and offers adjustable quotas for some AWS services.
How can you change the service quotas for your AWS account?
You can request an increase for service quotas for your AWS account directly from the Service Quotas console, AWS Support Center, or the AWS CLI.
What is the aim of AWS throttling?
Throttling in AWS aims to limit the number of requests that a user can send to an AWS service to prevent overuse of resources and ensure service availability to all users.
Can an AWS Service Quota be configured to work in a standby environment?
Yes. AWS service quotas can be configured to work in any environment including a standby or backup environment. This can be done through the AWS Management console or programmatically using the AWS CLI or SDKs.
How do you check the service quotas for your AWS managed services?
You can check the service quotas for your managed services via the AWS Service Quotas console or by using the ‘describe-services’ AWS CLI command.
Can service quotas be increased automatically in AWS?
No, service quotas cannot be increased automatically. However, you can request an increase in service quotas which is then reviewed and approved manually by the AWS team.
What happens when a service quota is exceeded in AWS?
When a service quota is exceeded in AWS, the excess requests are throttled and AWS returns a ‘RequestLimitExceeded’ error.
How can you handle throttling in AWS?
Throttling in AWS can be handled by implementing exponential backoff and jitter. This involves gradually increasing wait times between retries to reduce the load on the server and then randomizing these wait times to prevent simultaneous retries.
Is it possible to set custom quotas in AWS?
Yes, you can set custom quotas for several AWS services using AWS Service Quotas. This allows you to adjust quotas to meet the requirements of your specific use case.
What happens when you exceed the AWS general API request rate?
If the general API request rate is exceeded, AWS implements throttling which slows down the rate of requests to provide fair usage for all users.
Can you monitor your usage and service quotas through AWS CloudWatch?
Yes, you can use AWS CloudWatch to monitor the usage and quotas of your AWS services. AWS Service Quotas integrates with CloudWatch to provide metrics regarding quota usage.
How can you configure service quotas for a workload in a standby environment?
Configuring service quotas for a workload in a standby environment involves updating the quota settings for the services being used in that workload. This can be done via the Service Quotas page in AWS Management Console or programmatically via the AWS CLI or SDKs.
Can you bypass throttling in AWS?
Bypassing throttling is not generally recommended as it can lead to uneven resource usage. However, if necessary, you can request an increase in your service quotas to reduce the likelihood of throttling.
What are default service quotas in AWS?
Default service quotas are the maximum limit for a service that you can use without requesting an increase. These are designed to help prevent unintentional consumption of large amounts of resources.
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