CloudWatch

You can use the AWS Command Line Interface (CLI) to generate a PNG image of a metric graph from Amazon CloudWatch using the get-metric-widget-image command. This command allows you to specify a CloudWatch Metric Widget JSON definition and then retrieve the corresponding image in PNG format.

Look for valid values using

aws cloudwatch list-metrics --query "Metrics[].Namespace" --output text | sort | uniq

Filter down to a specific unit

aws cloudwatch list-metrics --namespace "AWS/EC2" --dimensions Name=InstanceId,Value=i-0123456789abcdef0

or something like

$ aws cloudwatch list-metrics \
  --namespace "AWS/S3" \
  --dimensions Name=BucketName,Value=mybucket

which returns

{
    "Metrics": [
        {
            "Namespace": "AWS/S3",
            "MetricName": "BucketSizeBytes",
            "Dimensions": [
                {
                    "Name": "BucketName",
                    "Value": "mybucket"
                },
                {
                    "Name": "StorageType",
                    "Value": "StandardStorage"
                }
            ]
        },
        {
            "Namespace": "AWS/S3",
            "MetricName": "NumberOfObjects",
            "Dimensions": [
                {
                    "Name": "BucketName",
                    "Value": "mybucket"
                },
                {
                    "Name": "StorageType",
                    "Value": "AllStorageTypes"
                }
            ]
        }
    ]
}

Now you can have a metrics set that looks like this:

{
  "metrics": [
    [ "AWS/S3", "NumberOfObjects", "BucketName", "mybucket" ]
  ],
  "period": 300,
  "stat": "Average",
  "region": "us-east-1",
  "title": "Bucket Size"
}

and then execute as

aws cloudwatch get-metric-widget-image --metric-widget '{
  "width": 600, 
  "height": 400, 
  "metrics": [
    [ "AWS/S3", "NumberOfObjects", "BucketName", "mybucket" ]
  ],
  "period": 300,
  "stat": "Average",
  "region": "us-east-1",
  "title": "Bucket Size",
  "view": "timeSeries",
  "start": "-PT1H",
  "end": "PT0H",
  "stacked": false,
  "yAxis": {"left": {"min": 0, "max": 100}}
}' --output-format json | jq -r '.MetricWidgetImage' | base64 --decode > widget_image.png

The last part with jq and base64 is important if calling from the AWS CLI, but will be different for calling directly as an API endpoint.