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Custom Metrics

5 minutes 5 Questions

Custom Metrics is an Auto Scaling feature that enables you to create and use your own application-specific metrics to drive the scaling decisions of your Auto Scaling groups. By using the CloudWatch API or the CloudWatch agent, you can collect, store, and analyze custom metrics that are relevant to your application, such as unique visitors, completed transactions, or user activity levels. You can then create alarms and scaling policies based on these custom metrics, giving you more fine-grained control over the scaling behavior of your applications. This allows you to tailor your scaling strategy to the specific needs of your application, ensuring that it scales up or down based on the most relevant and accurate indicators of demand.

Guide: Custom Metrics in AWS Solution Architect: Auto Scaling

What is it?
In Amazon Web Services (AWS), custom metrics are user-defined measures that are published to Amazon CloudWatch (a part of AWS auto scaling). These custom metrics give additional insights about the behavior of your applications, beyond standard metrics provided by AWS.
Why is it important?
Monitoring the performance of your applications is crucial, and using custom metrics allows you to create actionable alarms based on these metrics, or view more detailed statistics about your application resources. Custom metrics can monitor any aspect of your services which standard metrics may not cover, giving a holistic view of your services and allowing reactive and proactive responses to system behavior.
How does it work?
Custom metrics work by sending data to CloudWatch, which AWS will then monitor in real time. The frequency of your metrics depends on your needs, it could be every minute or less frequently. You can also store statistical data, set alarms or even automate actions based on custom metrics.
Exam Tips: Answering Questions on Custom Metrics
Understanding where and when to use custom metrics is key. Questions may ask about the functionality and benefit derived from using these metrics. A good tip is to revisit the AWS documentation and understand the theoretical and practical application of custom metrics. Remember, knowing the benefits of custom metrics, as in they fill in gaps standard metrics may not cover, will help in answering exam questions effectively.

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AWS Certified Solutions Architect - Auto Scaling Example Questions

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Question 1

You are monitoring an EC2 instance with an application that has a specific behavior during network requests. You want to be alerted if network request latency is above a certain threshold. Which of the following Custom Metrics is the best solution to implement?

Correct Answer: Create a Custom Metric by using the PutMetricData API to push network latency data outside the default Amazon CloudWatch Metrics.

The correct answer is to create a Custom Metric using the PutMetricData API because the provided scenario requires monitoring a specific behavior during network requests that is not available in the default Amazon CloudWatch Metrics. The other options do not address creating a custom metric or are not applicable to the scenario.

Question 2

A company wants to monitor a custom application's cache hit and cache miss rates using Amazon Cloudwatch. Which Custom Metric should be used to create a monitoring solution?

Correct Answer: Publish the application's cache hit and cache miss rates using the PutMetricData API to create a Custom Metric in CloudWatch.

The correct answer is to publish the application's cache hit and cache miss rates using the PutMetricData API to create a Custom Metric in CloudWatch. This allows monitoring the custom application's cache hit and miss rates in real-time. The other options do not address creating a Custom Metric or are not applicable to the scenario.

Question 3

A mobile app hosted on an EC2 instance requires monitoring the number of users that are currently active. Which of the following Custom Metrics in CloudWatch will help achieve this requirement?

Correct Answer: Create a Custom Metric using a script on the EC2 instance to send the current active users count to CloudWatch.

The correct option is to create a Custom Metric using a script on the EC2 instance to send the current active user count to CloudWatch, as it directly addresses the need to count active users in real-time. The other options either do not address active users count or do not involve creating a Custom Metric in CloudWatch.

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