CloudWatch metrics in AWS - Commands & Configuration

Introduction

CloudWatch metrics help you watch how your apps and servers are doing by collecting numbers about their work. This helps you find problems early and keep everything running smoothly.

When you want to see how much CPU your server is using over time.

When you need to check if your website is getting more visitors than usual.

When you want to get alerts if your app is using too much memory.

When you want to track how many errors your app has each hour.

When you want to compare performance before and after a change.

Commands

This command sends a custom metric called PageViews with a value of 100 to CloudWatch under the namespace MyApp. It helps you track how many pages were viewed.

Terminal

aws cloudwatch put-metric-data --namespace MyApp --metric-name PageViews --value 100 --unit Count

Expected Output

No output (command runs silently)

→

--namespace - Groups your metrics so you can find them easily.

→

--metric-name - Names the metric you are sending.

→

--value - Sets the number you want to record.

This command lists all metrics under the MyApp namespace so you can see what data is available.

Terminal

aws cloudwatch list-metrics --namespace MyApp

Expected Output

{

    "Metrics": [

        {

            "Namespace": "MyApp",

            "MetricName": "PageViews",

            "Dimensions": []

        }

    ]

}

→

--namespace - Filters metrics to only show those in the given group.

This command fetches the total PageViews metric data from June 1, 2024, between midnight and 1 AM, showing the sum per minute.

Terminal

aws cloudwatch get-metric-statistics --namespace MyApp --metric-name PageViews --start-time 2024-06-01T00:00:00Z --end-time 2024-06-01T01:00:00Z --period 60 --statistics Sum

Expected Output

{

    "Label": "PageViews",

    "Datapoints": [

        {

            "Timestamp": "2024-06-01T00:00:00Z",

            "Sum": 100.0,

            "Unit": "Count"

        }

    ]

}

→

--start-time - Sets the beginning of the time range for data.

→

--end-time - Sets the end of the time range for data.

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--statistics - Chooses the type of data summary to get, like Sum or Average.

Key Concept

If you remember nothing else from this pattern, remember: CloudWatch metrics let you send and view numbers about your apps to understand their health and performance.

Common Mistakes

Not specifying the correct namespace when sending or retrieving metrics.

Metrics won't appear where you expect, making them hard to find or missing in reports.

Always use the same namespace consistently for related metrics.

Using incorrect time format or range in get-metric-statistics command.

The command returns no data or errors because the time range is invalid.

Use ISO 8601 format with UTC time and ensure start-time is before end-time.

Not waiting enough time after sending metrics before trying to retrieve them.

Metrics may not be available immediately, causing empty results.

Wait a few minutes after put-metric-data before querying metrics.

Summary

Use aws cloudwatch put-metric-data to send custom numbers about your app.

Use aws cloudwatch list-metrics to see what metrics exist in a group.

Use aws cloudwatch get-metric-statistics to get detailed data for a metric over time.

Practice

1. What is the primary purpose of AWS CloudWatch metrics?

easy

A. To create virtual machines

B. To store files and documents securely

C. To monitor and track the performance of cloud resources

D. To manage user permissions

Solution

1. Step 1: Understand CloudWatch metrics role

   CloudWatch metrics collect data points about cloud resources like CPU usage or network traffic.

2. Step 2: Identify the main use

   This data helps monitor and keep cloud resources healthy and efficient.

3. Final Answer:

   To monitor and track the performance of cloud resources -> Option C

4. Quick Check:

   CloudWatch metrics = Monitor resources [OK]

Hint: CloudWatch metrics = numbers about resource health [OK]

Common Mistakes:

• Confusing metrics with storage services
• Thinking metrics create resources
• Mixing metrics with user management

2. Which of the following is the correct way to specify a metric namespace in AWS CloudWatch?

easy

A. Namespace: AWS/EC2

B. Namespace = AWS-EC2

C. Namespace -> AWS.EC2

D. Namespace is AWS_EC2

Solution

1. Step 1: Recall CloudWatch namespace format

   Namespaces use a string format with a slash, like AWS/EC2, to group metrics.

2. Step 2: Check each option format

   Only 'Namespace: AWS/EC2' uses the correct slash format without invalid characters.

3. Final Answer:

   Namespace: AWS/EC2 -> Option A

4. Quick Check:

   Namespace uses slash (/) format [OK]

Hint: Namespace uses slash (/) format, not dash or underscore [OK]

Common Mistakes:

• Using dash or underscore instead of slash
• Using equal sign instead of colon
• Using arrow notation incorrectly

3. Given the following CloudWatch metric data points for CPU utilization: [10, 20, 30, 40, 50], what is the average CPU utilization reported?

medium

A. 10

B. 25

C. 50

D. 30

Solution

1. Step 1: Sum all CPU utilization values

   10 + 20 + 30 + 40 + 50 = 150

2. Step 2: Calculate average by dividing sum by count

   150 / 5 = 30

3. Final Answer:

   30 -> Option D

4. Quick Check:

   Average = Sum / Count = 30 [OK]

Hint: Average = add all values, divide by number of values [OK]

Common Mistakes:

• Adding incorrectly
• Dividing by wrong count
• Picking max or min instead of average

4. You set a CloudWatch alarm to trigger when CPU utilization exceeds 70%, but it never triggers even when CPU is 80%. What is a likely cause?

medium

A. The metric period is too long, smoothing out spikes

B. The alarm threshold is set incorrectly below 70%

C. The alarm action is missing

D. The CPU utilization metric is disabled

Solution

1. Step 1: Understand alarm threshold and metric period

   The alarm triggers if average CPU exceeds 70% during the period.

2. Step 2: Identify effect of long metric period

   A long period averages out spikes, so short CPU spikes above 70% may not trigger alarm.

3. Final Answer:

   The metric period is too long, smoothing out spikes -> Option A

4. Quick Check:

   Long period averages hide spikes [OK]

Hint: Long metric periods smooth spikes, prevent alarms [OK]

Common Mistakes:

• Assuming threshold is set below 70%
• Ignoring missing alarm actions
• Thinking metrics can be disabled

5. You want to monitor the average latency of your web application every 5 minutes using CloudWatch. Which combination of settings is best to achieve this?

hard

A. Set metric period to 60 seconds and statistic to Sum

B. Set metric period to 300 seconds and statistic to Average

C. Set metric period to 300 seconds and statistic to Maximum

D. Set metric period to 60 seconds and statistic to Minimum

Solution

1. Step 1: Understand metric period and statistic

   Period defines how often data is collected; statistic defines how data is summarized.

2. Step 2: Match requirements to settings

   To monitor average latency every 5 minutes, use 300 seconds period and Average statistic.

3. Final Answer:

   Set metric period to 300 seconds and statistic to Average -> Option B

4. Quick Check:

   5 min period + Average = correct monitoring [OK]

Hint: Use 300s period and Average for 5-minute average latency [OK]

Common Mistakes:

• Using Sum or Maximum instead of Average
• Using 60s period for 5-minute average
• Confusing Minimum with latency monitoring