Instead of hard-coding server, application, and sensor names in your metric queries, you can use variables. The variables are listed as dropdown select boxes at the top of the dashboard. These dropdowns make it easy to change the display of data in your dashboard.
For an introduction to templating and template variables, refer to the [Templating]({{< relref "../../variables/_index.md" >}}) documentation.
You can use the following CloudWatch data source queries to specify the `Query Type` field in the Variable edit view. Use them to fill a variables options list with values like `regions`, `namespaces`, `metric names`, and `dimension keys/values`.
Read more about the available dimensions in the [CloudWatch Metrics and Dimensions Reference](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CW_Support_For_AWS.html).
| `Namespaces` | Returns a list of all the namespaces CloudWatch supports. |
| `Metrics` | Returns a list of metrics in the namespace. (specify region or use "default" for custom metrics) |
| `Dimension Keys` | Returns a list of dimension keys in the namespace. |
| `Dimension Values` | Returns a list of dimension values matching the specified `region`, `namespace`, `metric`, and `dimension_key`. You can use dimension `filters` to get more specific results. |
| `EBS Volume IDs` | Returns a list of volume ids matching the specified `region` and `instance_id`. |
| `EC2 Instance Attributes` | Returns a list of attributes matching the specified `region`, `attribute_name`, and `filters`. |
| `Resource ARNs` | Returns a list of ARNs matching the specified `region`, `resource_type` and `tags`. |
| `Statistics` | Returns a list of all the standard statistics. |
For details about the metrics CloudWatch provides, please refer to the [CloudWatch documentation](https://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/CW_Support_For_AWS.html).
You can specify [pre-defined filters of ec2:DescribeInstances](http://docs.aws.amazon.com/AWSEC2/latest/APIReference/API_DescribeInstances.html).
### Selecting attributes
Only 1 attribute per instance can be returned. Any flat attribute can be selected (i.e. if the attribute has a single value and isn't an object or array). Below is a list of available flat attributes:
