Tutorial / Cram Notes

Amazon CloudWatch is a monitoring service that provides data and actionable insights to monitor applications, understand and respond to system-wide performance changes, optimize resource utilization, and get a unified view of operational health. It collects monitoring and operational data in the form of logs, metrics, and events, providing you with a complete view of your AWS resources, applications, and services that run on AWS and on-premises servers.

When preparing for the AWS Certified DevOps Engineer – Professional (DOP-C02) exam, it is important to familiarize oneself with various CloudWatch metrics and logs provided by different AWS services.

CPU Utilization with Amazon EC2

EC2 instances provide several important metrics, with CPU utilization being one of the most critical. High CPU utilization may indicate that your instance is performing a lot of tasks and may need to be scaled up, whereas consistently low CPU utilization may suggest you can scale down to save costs.

The CPUUtilization metric measures the percentage of allocated compute units that are currently in use on the instance. This is a standard metric provided by AWS for EC2 instances without any additional charges.

Example of how to retrieve CPUUtilization metrics using AWS CLI:

aws cloudwatch get-metric-statistics –namespace AWS/EC2 –metric-name CPUUtilization –dimensions Name=InstanceId,Value=i-1234567890abcdef0 –statistics Average –start-time 2023-03-15T00:00:00Z –end-time 2023-03-15T23:59:00Z –period 300

Queue Length with Amazon RDS

For Amazon Relational Database Service (RDS), one of the important metrics to monitor is the DatabaseConnections, which provides the number of database connections in use.

However, for queue management within RDS, the DiskQueueDepth metric is crucial. This metric provides the number of outstanding IOs (read/write requests) waiting to access the disk. High values could be an indicator of a bottleneck in IO-heavy applications or insufficient disk capacity.

5xx Errors with Application Load Balancer (ALB)

With Application Load Balancers, one key metric to track is the HTTPCode_ELB_5XX_Count, which indicates the number of HTTP 5xx errors generated by the ALB. This is essential to troubleshoot and react to application errors that could be impacting end-user experiences.

These errors could be caused due to various issues such as server-side problems or a misconfiguration of the ALB.

Example of how to retrieve HTTPCode_ELB_5XX_Count metrics using AWS CLI:

aws cloudwatch get-metric-statistics –namespace AWS/ApplicationELB –metric-name HTTPCode_ELB_5XX_Count –dimensions Name=LoadBalancer,Value=app/my-load-balancer/50dc6c495c0c9188 –statistics Sum –start-time 2023-03-15T00:00:00Z –end-time 2023-03-15T23:59:00Z –period 300

CloudWatch Logs

CloudWatch Logs can collect, monitor, analyze and store your log files from various sources. For instance, logs from EC2 instances can highlight application performance issues, while ALB logs can provide detailed information about HTTP requests processed by the load balancer.

Enabling log collection for these services is straightforward and can be done through the AWS Management Console or using the AWS CLI.

These logs can be further analyzed using query syntax to extract useful metrics, patterns, or insights.

Summary Table of Common Metrics

Here is a table of some commonly used AWS CloudWatch metrics by service:

AWS Service Metric Name Description
EC2 CPUUtilization The percentage of allocated EC2 compute units that are currently in use.
RDS DatabaseConnections The number of database connections in use.
DiskQueueDepth The number of outstanding IOs (read/write requests) waiting to access the disk.
Application LB HTTPCode_ELB_5XX_Count The number of HTTP 5xx error codes generated by the ALB.
RequestCount The number of requests processed by the ALB.

This is not an exhaustive list, but understanding and monitoring these metrics can provide significant insights into the health and performance of your AWS applications and services. During the DOP-C02 exam, being familiar with these metrics, how to access them, and interpret their values is crucial for successfully managing AWS resources and optimizing performance.

Practice Test with Explanation

True or False: CloudWatch can natively monitor the memory usage of an EC2 instance without any custom metrics.

  • A) True
  • B) False

Answer: B) False

Explanation: CloudWatch does not monitor memory usage by default. You must install CloudWatch agent on the instance to collect and send memory usage metrics to CloudWatch.

When monitoring an Application Load Balancer, which metric can indicate that the backend is not processing requests quickly enough?

  • A) HTTPCode_Backend_4XX
  • B) Latency
  • C) SurgeQueueLength
  • D) TargetResponseTime

Answer: B) Latency

Explanation: The Latency metric measures the time taken to send the request to the backend and receive a response. High latency can indicate that the backend is slow to process requests.

True or False: The BurstBalance metric in Amazon RDS allows you to monitor the balance of burstable performance credits for a DB instance.

  • A) True
  • B) False

Answer: A) True

Explanation: The BurstBalance metric represents the percentage of General Purpose SSD (gp2) burst-bucket I/O credits available for a burstable performance RDS DB instance.

Which CloudWatch metric can be used to monitor the health of an EC2 instance’s underlying hardware?

  • A) StatusCheckFailed_System
  • B) CPUUtilization
  • C) NetworkIn
  • D) DiskReadOps

Answer: A) StatusCheckFailed_System

Explanation: StatusCheckFailed_System checks the health of the EC2 instance’s hardware. An unhealthy instance might need to be stopped and restarted or replaced.

True or False: The WriteIOPS metric is available for Amazon RDS instances to monitor the number of write operations per second.

  • A) True
  • B) False

Answer: A) True

Explanation: The WriteIOPS metric is used to monitor the number of write disk I/O operations to an RDS instance, showcasing the write load on the database.

Which metric is useful for monitoring the inbound traffic to an EC2 instance?

  • A) NetworkPacketsIn
  • B) TCPConnections
  • C) NetworkIn
  • D) DiskReadBytes

Answer: C) NetworkIn

Explanation: NetworkIn metric measures the number of bytes received on all network interfaces by the EC2 instance, indicating the inbound traffic volume.

Is the RequestCount metric available in CloudWatch for monitoring requests to an Application Load Balancer (ALB)?

  • A) Yes
  • B) No

Answer: A) Yes

Explanation: The RequestCount metric tracks the number of requests that are routed to all targets by the ALB, which helps in understanding the application load.

True or False: CloudWatch Logs can natively interpret and provide insights from log data without the need for any filtering or analysis.

  • A) True
  • B) False

Answer: B) False

Explanation: CloudWatch Logs can store and monitor log files, but insights require setting up metric filters, queries, or using CloudWatch Logs Insights for interpreting the log data.

The DatabaseConnections metric for Amazon RDS is used to:

  • A) Measure the CPU utilization of the RDS instance
  • B) Monitor the transaction logs
  • C) Monitor the number of active connections to the RDS instance
  • D) Measure the available disk space

Answer: C) Monitor the number of active connections to the RDS instance

Explanation: DatabaseConnections metric is used to determine the number of active connections to the RDS database, which can help assess if the database is nearing its connection limit.

In CloudWatch, what does the metric HealthyHostCount indicate when monitoring an Elastic Load Balancer (ELB)?

  • A) The total number of requests sent to the load balancer
  • B) The average latency for the requests processed
  • C) The CPU utilization of hosts behind the load balancer
  • D) The number of healthy instances registered with the load balancer

Answer: D) The number of healthy instances registered with the load balancer

Explanation: HealthyHostCount represents the number of instances that are considered healthy by the load balancer’s health checks, which can help to identify issues with the backend instances.

Amazon CloudWatch can automatically react to changes in your AWS resources based on user-defined thresholds.

  • A) True
  • B) False

Answer: A) True

Explanation: Users can create CloudWatch alarms that trigger automatic actions when a specified metric crosses a defined threshold, indicating the ability to react to changes in AWS resources autonomously.

True or False: CloudWatch Logs can be used to monitor and track API calls made to AWS services using AWS CloudTrail.

  • A) True
  • B) False

Answer: A) True

Explanation: CloudWatch Logs can be integrated with AWS CloudTrail to monitor, store, and access log files that track API calls to AWS services, providing security and compliance monitoring.

Interview Questions

What is the significance of monitoring CPU utilization for Amazon EC2 instances in CloudWatch, and how can it impact your application performance?

Monitoring CPU utilization is crucial because it helps in understanding the compute load on an EC2 instance. High CPU usage may indicate that the instance is under-provisioned and struggling to handle the workload, which can lead to degraded performance or even service outages. Conversely, consistently low CPU utilization might suggest over-provisioning, leading to unnecessary costs. By carefully monitoring CPU utilization, DevOps engineers can make informed decisions about scaling and cost optimization.

How can monitoring queue length in Amazon RDS with CloudWatch help maintain database performance, and what actions can be taken based on this metric?

Queue length in Amazon RDS represents the number of disk I/O operations that are waiting to be written to or read from the disk. Monitoring this metric helps in identifying bottlenecks in data processing and potential performance issues. A consistently high queue length could suggest the need for better I/O capacity or optimized query performance. Actions such as increasing provisioned IOPS, optimizing queries, or scaling up the database instance size might be considered based on this metric.

What are 5xx errors in the context of an Application Load Balancer (ALB) and why is it important to monitor them using CloudWatch?

5xx errors represent server-side errors that occur when the ALB receives a request but cannot get a proper response from the target’s back-end servers. Monitoring these errors is critical because they indicate issues with the application or infrastructure that need immediate attention to ensure service availability and to provide a smooth user experience. High numbers of 5xx errors may require investigation into application code, server health, or capacity issues.

In CloudWatch, how would you set up an alarm for high CPU utilization for an EC2 instance, and what actions would you configure in response to this alarm?

To set up an alarm in CloudWatch for high CPU utilization on an EC2 instance, navigate to the CloudWatch dashboard, create a new alarm, and specify the EC2 metric for CPU Utilization. Define the threshold that signifies high CPU usage and the period over which the metric should be evaluated. In response to the alarm, you could configure actions such as sending notifications, triggering an Auto Scaling policy to scale out the EC2 fleet, or executing an AWS Lambda function to perform an automated task.

Can you explain the difference between CloudWatch Logs and CloudWatch Metrics, and provide examples where each would be used?

CloudWatch Logs are used for monitoring, storing, and accessing log files from EC2 instances, AWS CloudTrail, and other sources. They provide detailed information about specific events and are useful for troubleshooting. For example, they can be used to track application errors or security incidents. CloudWatch Metrics, on the other hand, provides a more aggregate view of system performance, such as CPU utilization, network I/O, or disk read/write operations. These are used for real-time monitoring of resources and setting alarms based on thresholds.

How can you use CloudWatch to monitor memory usage on your Amazon EC2 instances, given that memory utilization is not a metric provided by AWS out of the box?

Memory usage monitoring on EC2 instances requires custom metrics. You can use the CloudWatch agent or custom scripts to collect memory usage data from the instance and push it to CloudWatch as a custom metric. Once the data is in CloudWatch, you can view, graph, and set alarms on memory utilization just like any other metric.

What CloudWatch metric would you use to monitor the read/write throughput of your Amazon RDS instance, and why is this important?

The ReadThroughput and WriteThroughput metrics in CloudWatch should be used to monitor the I/O throughput of an Amazon RDS instance. Monitoring these metrics is important because they provide insights into the volume of data the application reads from and writes to the database, which is directly related to the database performance and the application’s responsiveness.

How can CloudWatch Logs help you identify and diagnose application issues, and what features does CloudWatch provide to search and analyze log data?

CloudWatch Logs helps in identifying and diagnosing application issues by allowing the collection and analysis of log data. It provides features like log groups and log streams to organize logs, and you can search and filter log data using query language. Moreover, CloudWatch Logs Insights provides an interactive interface to explore, analyze, and visualize your log data, helping you quickly find the root cause of issues.

What are some common CloudWatch metrics you would monitor for an Amazon DynamoDB table and why?

Common CloudWatch metrics for DynamoDB include ReadCapacityUnits and WriteCapacityUnits (providing insight into provisioned capacity utilization), ConsumedReadCapacityUnits and ConsumedWriteCapacityUnits (showing the level of consumed capacity), ThrottledRequests (indicating whether requests are being throttled due to capacity limits), and ConditionalCheckFailedRequests (useful to monitor failed conditional writes). Monitoring these metrics is important to ensure that your DynamoDB table has sufficient capacity to meet demand and maintain performance.

What benefits does integrating Amazon CloudWatch with AWS Auto Scaling provide?

Integrating CloudWatch with AWS Auto Scaling allows you to dynamically adjust the number of instances in response to real-time changes in demand, based on CloudWatch metrics like CPU utilization, network I/O, and custom metrics. This ensures that you maintain optimal application performance and cost-efficiency by scaling the infrastructure automatically according to defined policies.

Explain a scenario where you would use CloudWatch Events and the actions you could automate following a specific event.

CloudWatch Events can be used to respond to state changes in AWS resources. For example, you could create an event rule to trigger an AWS Lambda function or send an SNS notification when an Auto Scaling group launches or terminates EC2 instances. This helps automate workflows and quickly respond to infrastructure changes without manual intervention.

When configuring an alarm, why is it essential to set the appropriate period for a CloudWatch metric, and what considerations should you take into account?

Setting the appropriate period for a CloudWatch metric is essential because it defines the time length over which data points are aggregated into a single metric for evaluation. If the period is too short, the alarm may trigger too often, including false positives. If the period is too long, you may miss quick spikes or drop-offs in performance. You should consider the nature of the workload, metric volatility, and the responsiveness required when choosing the period.

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Elmer Warren
6 months ago

The tutorial on AWS Certified DevOps Engineer is really insightful! I particularly enjoyed learning about monitoring CPU utilization with CloudWatch on Amazon EC2.

Frank Fields
6 months ago

I agree – the explanation of how CloudWatch logs work with AWS services like RDS and ALB was very useful!

Liam Moore
6 months ago

Can someone explain how to set an alarm for high CPU utilization on an EC2 instance using CloudWatch?

Volker Vidal
5 months ago

How often should I check my RDS queue length to ensure optimal performance?

Phoebe Thomas
6 months ago

Thanks for the valuable post!

Teodora Ćirković

I appreciate the detailed explanation on managing 5xx errors with an Application Load Balancer.

Herlinde Richter
6 months ago

Is there any way to filter specific 5xx error codes using CloudWatch logs?

Erin Daniels
6 months ago

Love the way the tutorial breaks down complex topics. Kudos!

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