CloudWatch Dashboard to manage & monitor a budget

Question

In CloudWatch dashboard, is it possible to use math expressions (e.g. based on EstimatedCharges or some other metric) to create a metric that shows a budget, with month-to-month cloud spending gradually deducted from that budget?

Example: Suppose there is a starting budget of $1000. The cloud spend is $200 in the first month, and $100 in the second. Hence, the metric needs to have an initial value of $1000, which decreases to $800 at the end of the first month, and $700 at the end of the second month.

Can I use CloudWatch Dashboards with math expressions for this, or would other services be needed? e.g. QuickSight, Lambda?

Answer

Your use case might be met using AWS Budgets? For more details see https://aws.amazon.com/aws-cost-management/aws-budgets/.

Answer

This graph would be approximately what you need, where you are plotting ```1000 less the running total of your estimate spend```.

```
{
    "metrics": [
        [ { "expression": "1000 - RUNNING_SUM(monthly)", "label": "Expression1", "id": "budget" } ],
        [ "AWS/Billing", "EstimatedCharges", "Currency", "USD", { "id": "monthly", "visible": false } ]
    ],
    "view": "timeSeries",
    "stacked": false,
    "region": "us-east-1",
    "stat": "Maximum",
    "period": 2592000
}
```

However, it is difficult to get exact value of spend in a month.  To get exact values you would be better off querying [AWS Cost Explorer](https://aws.amazon.com/aws-cost-management/aws-cost-explorer/).  CloudWatch Dashboards has a [Custom Widget](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/add_custom_widget_samples.html) feature that comes with a simple **AWS Cost Explorer report**. It would be relatively easy to adapt the code in that to display what you need.

CloudWatch Dashboard to manage & monitor a budget

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