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)

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

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

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--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": []

        }

    ]

}

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--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"

        }

    ]

}

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

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--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.