Tutorial / Cram Notes
CloudWatch alarms watch a single metric over a specified time period, and perform one or more actions based on the value of the metric relative to a given threshold. The alarms can send notifications or automatically make changes to the resources you are monitoring when a threshold is breached. For example, an alarm could send a notification when the CPU utilization of an EC2 instance exceeds a certain percentage, or when network throughput falls below a particular baseline.
Creating a CloudWatch Alarm
To create a CloudWatch alarm that triggers when certain conditions are met, you can use the AWS Management Console, AWS CLI, or CloudWatch API. Here’s a high-level step-by-step process using the AWS Management Console:
- Navigate to the CloudWatch service in the AWS Management Console.
- In the navigation pane, click Alarms and then click Create Alarm.
- In the Create Alarm wizard, select the metric you want to monitor, such as network packets in/out on a specific EC2 instance.
- Specify the criteria for your alarm. For instance, you might want to trigger an alarm if the network input exceeds 10,000 packets for three consecutive periods of 5 minutes.
- Define the actions to take when the alarm state is met. This could be to notify an SNS topic or take auto-scaling actions.
- Give your alarm a name and an optional description.
- Click Create Alarm.
Example of a CloudWatch Alarm Using AWS CLI
The following is an example of how to create a CloudWatch alarm using the AWS Command Line Interface (CLI) to monitor an EC2 instance’s CPU utilization:
aws cloudwatch put-metric-alarm –alarm-name HighCPUUtilization –namespace AWS/EC2 –metric-name CPUUtilization –statistic Average –dimensions Name=InstanceId,Value=i-1234567890abcdef0 –period 300 –evaluation-periods 2 –threshold 80 –comparison-operator GreaterThanThreshold –alarm-actions arn:aws:sns:us-west-2:111122223333:MyTopic –unit Percent
This command creates an alarm named HighCPUUtilization that will trigger if the average CPU utilization of the specified EC2 instance is greater than 80% for two consecutive periods of 5 minutes.
Use Cases for CloudWatch Alarms in Advanced Networking
- Network Throughput Monitoring: Setting alarms for network throughput metrics can help ensure that your networking infrastructure is performing as expected. For instance, you could set an alarm to notify you if network throughput for a critical application goes below a certain threshold potentially indicating congestion or other issues.
- Bandwidth Billing Alerts: Bandwidth can incur significant costs. You can set alarms to get notified when estimated charges for data transfer are above your expected range, which can help control costs.
- VPN Monitoring: You might set up a CloudWatch alarm to monitor the health of a VPN connection. If the tunnel status changes, which could impact connectivity, a CloudWatch alarm can send a notification to take corrective action.
Comparing CloudWatch Alarms and CloudTrail
While CloudWatch alarms are great for monitoring real-time performance metrics and setting alerts based on thresholds, AWS CloudTrail is used for logging and tracking API calls across your AWS infrastructure. CloudTrail helps with compliance audits, tracking resource changes, and troubleshooting operational issues by providing a history of AWS API calls for an account.
| Feature | CloudWatch Alarms | CloudTrail |
|---|---|---|
| Purpose | Real-time monitoring and alerts | Logging and tracking API calls |
| Use Case | Performance metrics, operational health | Compliance, auditing, resource change tracking |
| Operational Timeframe | Real-time | Historical |
| Customization | Metric thresholds, evaluation periods | Event selectors, data events |
| Response | Notifications, automated actions | Log files to S3, CloudWatch Logs integration |
Understanding when to use CloudWatch alarms and when to combine them with other services such as CloudTrail is vital for creating a robust and secure AWS networking infrastructure. These concepts are critical when preparing for the AWS Certified Advanced Networking – Specialty (ANS-C01) exam, ensuring that you are adept at managing and alerting on your network’s operational health and security.
Practice Test with Explanation
(True/False) AWS CloudWatch can monitor AWS resources and applications in real-time.
- True
True
AWS CloudWatch can monitor AWS resources and applications in real-time, providing metrics and logs that can be used to set alarms and take automated actions.
(Single Select) What does an Amazon CloudWatch alarm do when it changes state?
- A) It sends an update to an Amazon Simple Notification Service (SNS) topic.
- B) It automatically resolves the issue causing the alarm.
- C) It increases the EC2 instance size to handle the load.
- D) It creates a snapshot of the EC2 instance.
A
Amazon CloudWatch alarms send updates to an Amazon SNS topic when they change state, which can then notify the appropriate personnel or trigger automated actions.
(Multiple Select) Which of the following metrics are provided by Amazon CloudWatch by default for Amazon EC2 instances? (Select TWO)
- A) Disk read/write bytes
- B) Memory utilization
- C) CPU utilization
- D) Network in/out
A, C
By default, Amazon CloudWatch provides metrics such as disk read/write bytes and CPU utilization for EC2 instances, but memory utilization needs to be monitored using custom metrics.
(True/False) Amazon CloudWatch alarms can only be set for existing metrics, not custom metrics.
- False
False
Amazon CloudWatch alarms can be set for both existing metrics and custom metrics that you can define based on specific needs for your application.
(Single Select) Which of the following is NOT a valid state for a CloudWatch alarm?
- A) INSUFFICIENT_DATA
- B) ALARM
- C) OK
- D) DISABLED
D
The valid states for a CloudWatch alarm are ALARM, OK, and INSUFFICIENT_DATA. There is no “DISABLED” state; instead, alarms can be enabled or disabled.
(Multiple Select) Which actions can be triggered by a CloudWatch Alarm? (Select TWO)
- A) Automatically creating an Amazon Machine Image (AMI) of an instance
- B) Sending a notification to an Amazon SNS topic
- C) Auto-scaling an EC2 instance group
- D) Initiating an AWS Lambda function
B, C
CloudWatch alarms can trigger various actions, such as sending a notification to an SNS topic or auto-scaling an EC2 instance group. Creating an AMI or initiating a Lambda function requires additional integration.
(True/False) CloudWatch alarms can be set up to monitor the estimated charges on your AWS account.
- True
True
CloudWatch alarms can be set up to monitor the estimated charges on your AWS account, providing an alert when charges exceed a certain threshold.
(Single Select) What is a prerequisite for creating a CloudWatch alarm on EC2 instance memory utilization?
- A) Installing the Amazon Inspector Agent
- B) Installing a third-party monitoring tool
- C) Configuring AWS Config
- D) Installing the CloudWatch agent on the instance
D
To create a CloudWatch alarm on EC2 instance memory utilization, you must install the CloudWatch agent on the instance since memory utilization is a custom metric.
(True/False) CloudWatch alarms can be used to directly stop or terminate an Amazon EC2 instance when certain criteria are met.
- True
True
CloudWatch alarms can be configured to automatically stop or terminate an Amazon EC2 instance when certain conditions are met by integrating with EC2 actions.
(Multiple Select) For which of the following AWS services can CloudWatch alarms be set up for monitoring? (Select TWO)
- A) Amazon S3
- B) Amazon Aurora
- C) Amazon Kinesis
- D) AWS Direct Connect
B, C
CloudWatch alarms can be set up for various AWS services, including Amazon Aurora and Amazon Kinesis, allowing for the monitoring of database performance or stream data, respectively. Direct Connect does not provide direct CloudWatch metrics, and S3 requires additional configuration as CloudWatch primarily monitors operational metrics like bucket-level operations not storage size directly.
(Single Select) Which Amazon CloudWatch feature allows the correlation of logs and metrics for a set of resources?
- A) CloudWatch Alarms
- B) CloudWatch Logs
- C) CloudWatch Dashboards
- D) CloudWatch Insights
D
CloudWatch Insights allows users to analyze and correlate logs and metrics, making it easier to understand and respond to operational issues across a set of resources.
(True/False) CloudWatch Logs can trigger a CloudWatch Alarm.
- True
True
CloudWatch Logs can trigger a CloudWatch Alarm based on the occurrence of specific log events, allowing for automated alerting and actions based on log data patterns.
Interview Questions
Sample Interview/Exam Questions on AWS CloudWatch Alarms:
What are the key components that make up an Amazon CloudWatch alarm?
The key components are a metric, a threshold, an evaluation period, and alarm actions.
How can Amazon CloudWatch alarms be used to monitor network traffic in AWS?
CloudWatch alarms can be set on network-related metrics such as NetworkIn and NetworkOut for AWS resources to monitor traffic thresholds, with alerts triggered if these thresholds are crossed.
Can you explain the difference between CloudWatch metrics and logs when setting up alerts?
CloudWatch Metrics provide a numerical representation of data over time, which can be used to trigger alarms, while Logs provide a more detailed, granular view of event-driven data that can be monitored for specific patterns or keywords.
In what scenarios would you prefer to use anomaly detection with CloudWatch alarms over static thresholds?
Anomaly detection is best used when the expected metrics have unpredictable patterns, so this feature can dynamically adjust thresholds to reduce false alerts.
What is the difference between the “ALARM” and the “INSUFFICIENT_DATA” state for a CloudWatch alarm?
“ALARM” state indicates that the defined threshold has been breached, while “INSUFFICIENT_DATA” state indicates that the alarm has just started, stopped, or lacks the data to determine the alarm state.
How can you set up a CloudWatch alarm to recover an EC2 instance when it becomes impaired?
This can be done by creating an alarm that watches for the EC2 status check, and configuring the alarm’s action to recover the impaired instance.
What steps are involved in creating a CloudWatch alarm for an AWS service such as RDS or EC2?
Steps include: selecting the service and metric, defining the threshold and conditions for the alert, setting the evaluation period, and configuring the actions to be taken when the alarm state is reached.
How would you integrate AWS CloudWatch with AWS SNS to notify an administrator in case of an alarm?
By setting up an SNS topic, subscribing an administrator’s email address or phone number to the topic, and then assigning that SNS topic to the CloudWatch alarm’s action.
How can you ensure CloudWatch alarms are as cost-effective as possible while still maintaining effective monitoring?
By choosing the appropriate alarm frequency (periods) and evaluation periods, opting for anomaly detection over static thresholds where practical, and combining alerts with EC2 Auto Scaling and other management tools as required.
Can you use AWS CloudWatch to set alarms on custom application metrics? If so, how would you go about it?
Yes, by sending custom application metrics to CloudWatch using the PutMetricData API, and then creating alarms based on those custom metrics.
What is the role of CloudWatch alarm “actions” and give an example of an automated action that could be triggered by an alarm?
Alarm “actions” define what should happen when an alarm changes state. An example of an automated action could be autoscaling an EC2 instance group; increasing the number of instances when a CPU Utilization threshold is breached.
How can CloudWatch alarms help in maintaining compliance with network performance standards?
Alarms can be set to notify when service level agreements (SLAs) are at risk of being breached, such as continuously high latency or low throughput, allowing for proactive remediation.
This tutorial on AWS Certified Advanced Networking – Specialty (ANS-C01) is fantastic! I found the section on CloudWatch alarms particularly useful.
Agreed, I think understanding CloudWatch alarms is crucial for anyone preparing for the ANS-C01 exam. The blog post covered it comprehensively.
Can someone explain how CloudWatch alarms interact with SNS for alert notifications?
Excellent blog post, very detailed!
I think the part about metric filters could use a bit more clarification.
Who else finds the integration between CloudWatch and Lambda super effective for automating responses?
The diagram showing the flow of alarm states was very helpful. Thanks!
Is it possible to trigger an ASG (Auto Scaling Group) scaling policy using a CloudWatch alarm?