Concepts
A CloudWatch alarm watches a single metric and sends notifications or automatically makes changes to the resources you are monitoring when the metric breaches a threshold you set. Alarms can be used for monitoring CPU utilization, disk I/O, network data, or any custom metric that you define.
Alarms have three states:
- OK: The metric is within the defined threshold.
- ALARM: The metric is outside of the defined threshold.
- INSUFFICIENT_DATA: The alarm has just started but hasn’t yet accumulated enough data to determine the metric’s state.
Creating CloudWatch Alarms
Step 1: Open the CloudWatch Console
To create a CloudWatch alarm, you first need to navigate to the CloudWatch dashboard in the AWS Management Console.
Step 2: Navigate to Alarms
Once you are in the CloudWatch dashboard, go to the “Alarms” section where you can create and manage your CloudWatch alarms.
Step 3: Specify Metric and Conditions
Next, you specify the metric you want to monitor. This involves selecting the namespace, the metric name, and the statistics, such as Average, Sum, Minimum, or Maximum. You then set the threshold by defining when the alarm state should change.
Step 4: Configure Actions
After specifying the metric and conditions, you set the actions that should take place when an alarm state is reached. These actions can include sending a notification to an Amazon Simple Notification Service (SNS) topic, auto-scaling actions, or EC2 instance actions such as stopping, terminating, or recovering an instance.
Step 5: Add Name and Description
Finally, you give your alarm a unique name and a description so that you can identify and manage it within the CloudWatch console.
Example: Creating a CPU Utilization Alarm
Imagine you want to create an alarm that monitors the CPU utilization of an EC2 instance and sends a notification if the CPU usage is above 80% for more than 5 minutes.
1. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/
2. In the navigation pane, click on ‘Alarms’ and then ‘Create Alarm’.
3. Click on ‘Select metric’, choose EC2 -> Per-Instance Metrics, and select the metric ‘CPUUtilization’.
4. For the statistic, choose ‘Average’ and set the period to ‘5 minutes’.
5. Set the threshold type to ‘Static’.
6. Define the Alarm condition. For example, ‘Greater/Equal’ than 80% over 5 minutes.
7. In the Actions section, configure the action to ‘Notify me’, and select an SNS topic or create a new one.
8. Name your alarm, e.g., ‘High CPU Utilization’ and provide a description.
9. Click on ‘Create Alarm’.
Best Practices for CloudWatch Alarms
When creating CloudWatch alarms, it’s essential to follow best practices:
- Descriptive Names: Choose descriptive names for your alarms that reflect the metric being monitored and the expected outcome.
- Relevant Thresholds: Set thresholds that are relevant to the application’s performance and do not generate false positives/negatives.
- Alarm Fatigue: Avoid too many unnecessary alarms that could lead to alarm fatigue.
- Period and Evaluation Periods: Choose the correct period and evaluation periods that suit your use case. The period is the granularity of the metric data, and the evaluation period is how many consecutive periods need to breach the threshold.
- Multiple Notifications: Use multiple notifications for different levels of severity. You can have an Informational notification as well as a Critical notification for the same metric.
By utilizing CloudWatch alarms, AWS Certified SysOps Administrators can effectively monitor AWS resources and ensure that appropriate actions are taken if and when specified conditions are met. Remember that persistently evaluating and adjusting your CloudWatch alarms is key to maintaining a well-monitored and responsive AWS environment.
Answer the Questions in Comment Section
True or False: You can only set CloudWatch alarms on metrics provided by AWS services by default.
False
You can set alarms on both the default metrics provided by AWS services and custom metrics that you can send to CloudWatch.
A CloudWatch alarm can be set to notify an administrator via which of the following methods?
- a) Email
- b) SMS
- c) Creating an Auto Scaling policy
- d) All of the above
d) All of the above
A CloudWatch alarm can perform several actions, such as sending notifications via Amazon SNS (which supports email and SMS), initiating Auto Scaling policies, and more.
True or False: A CloudWatch alarm can trigger an instance recovery for an EC2 instance when it becomes impaired.
True
CloudWatch alarms can be configured to automatically recover an impaired EC2 instance, ensuring high availability.
CloudWatch alarms can be created for which types of metrics?
- a) Standard resolution metrics
- b) High-resolution metrics
- c) Both a) and b)
- d) None of the above
c) Both a) and b)
CloudWatch supports alarms for standard (5-minute granularity) and high-resolution (1-minute or less granularity) metrics.
When creating a CloudWatch alarm, what is the evaluation period?
- a) The length of time to wait before the first check
- b) The number of metric data points to compare to the threshold
- c) A predefined time period that cannot be modified
- d) The interval at which data is sampled
b) The number of metric data points to compare to the threshold
The evaluation period is the number of the most recent data points to use for comparing against the threshold to determine the alarm state.
True or False: Once a CloudWatch alarm is set, it cannot be edited; it must be deleted and recreated for any modifications.
False
You can edit most properties of a CloudWatch alarm, including its name, metric, conditions, periods, and actions.
Which of the following actions can be taken by a CloudWatch alarm?
- a) Launch an EC2 instance
- b) Send a notification to an SNS topic
- c) Terminate an EC2 instance
- d) Send an alert to AWS Support
b) Send a notification to an SNS topic
A common action taken by CloudWatch alarms is to send notifications to an Amazon SNS topic. Other actions, such as instance launch/termination, can be managed through other AWS services in response to an alarm.
True or False: You can set an alarm to notify you if a metric is above or below a predefined threshold for a specified period.
True
CloudWatch alarms can monitor a specific metric over a specified time period and perform actions if the value of the metric goes above or below the defined threshold.
What is the minimum granularity for a CloudWatch metric that you can set an alarm on?
- a) 1 minute
- b) 5 minutes
- c) 10 minutes
- d) 1 hour
a) 1 minute
While standard metrics have a granularity of 5 minutes, CloudWatch alarms can be set on high-resolution metrics with a granularity of up to 1 minute.
True or False: CloudWatch alarms have to be associated with a specific AWS region.
True
CloudWatch metrics and alarms are region-specific. You need to set and manage alarms within the region where the resource exists.
What happens if a CloudWatch alarm’s state is “INSUFFICIENT_DATA”?
- a) The alarm performs the action as if in the ALARM state
- b) The alarm performs the action as if in the OK state
- c) The alarm does not perform any actions
- d) The alarm state is manually set by the user
c) The alarm does not perform any actions
When an alarm is in the INSUFFICIENT_DATA state, it means there isn’t enough data for it to determine the metric’s state relative to the threshold. In this state, the alarm does not perform any actions.
Can you set a CloudWatch alarm on a metric representing the estimated charges on your AWS account?
- a) Yes
- b) No
a) Yes
You can set an alarm on the metric for estimated charges on your AWS account to notify you when your usage costs exceed your budgeted amount. This metric is available in the Billing and Cost Management console and gets reported to CloudWatch.
This blog post is really helpful for understanding CloudWatch alarms in the AWS Certified SysOps Administrator exam.
Can someone explain the difference between Metric Alarms and Composite Alarms?
I get confused with creating CloudWatch Alarms for EC2 instances. Any tips?
Great article! It helped me set up my first CloudWatch Alarm without issues.
How can I use CloudWatch Alarms with Auto Scaling groups?
Thanks for this post. It clarified a lot of my doubts!
Can CloudWatch Alarms integrate with third-party services?
Loved the deep dive into CloudWatch Alarms. Very thorough!