cloudwatch metrics datasource

[wardviaene]

A few notes:

• There is no resource to create a metric, so the test includes a PutMetricData to create a custom metric.
• The output of this datasource is a list of maps, because you typically want to retrieve more than one metric.
• One use-case is to retrieve all EC2 instances or RDS instances to create alarms for specific metrics.

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Closes #3644

Release note for CHANGELOG:

datasource/aws_cloudwatch_metrics: Get metrics from CloudWatch

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccAWSCloudwatchMetricsDataSource_basic'
-run=TestAccAWSCloudwatchMetricsDataSource_basic'==> Checking that code complies with gofmt requirements...TF_ACC=1 go test ./aws -v -count 1 -parallel 20 -run=TestAccAWSCloudwatchMetricsDataSource_basic -timeout 120m
=== RUN   TestAccAWSCloudwatchMetricsDataSource_basic
=== PAUSE TestAccAWSCloudwatchMetricsDataSource_basic
=== CONT  TestAccAWSCloudwatchMetricsDataSource_basic
--- PASS: TestAccAWSCloudwatchMetricsDataSource_basic (159.96s)
PASS
ok      github.com/terraform-providers/terraform-provider-aws/aws       161.487s
...

[teamterraform]

Notification of Recent and Upcoming Changes to Contributions

Thank you for this contribution! There have been a few recent development changes that affect this pull request. We apologize for the inconvenience, especially if there have been long review delays up until now. Please note that this is automated message from an unmonitored account. See the FAQ for additional information on the maintainer team and review prioritization.

If you are unable to complete these updates, please leave a comment for the community and maintainers so someone can potentially continue the work. The maintainers will encourage other contributors to use the existing contribution as the base for additional changes as appropriate. Otherwise, contributions that do not receive updated code or comments from the original contributor may be closed in the future so the maintainers can focus on active items.

For the most up to date information about Terraform AWS Provider development, see the Contributing Guide. Additional technical debt changes can be tracked with the technical-debt label on issues.

As part of updating a pull request with these changes, the most current unit testing and linting will run. These may report issues that were not previously reported.

Terraform 0.12 Syntax

Reference: #8950
Reference: #14417

Version 3 and later of the Terraform AWS Provider, which all existing contributions would potentially be added, only supports Terraform 0.12 and later. Certain syntax elements of Terraform 0.11 and earlier show deprecation warnings during runs with Terraform 0.12. Documentation and test configurations, such as those including deprecated string interpolations (some_attribute = "${aws_service_thing.example.id}") should be updated to the newer syntax (some_attribute = aws_service_thing.example.id). Contribution testing will automatically fail on older syntax in the near future. Please see the referenced issues for additional information.

Action Required: Terraform Plugin SDK Version 2

Reference: #14551

The Terraform AWS Provider has been upgraded to the latest version of the Terraform Plugin SDK. Generally, most changes to contributions should only involve updating Go import paths in source code files. Please see the referenced issue for additional information.

Removal of website/aws.erb File

Reference: #14712

Any changes to the website/aws.erb file are no longer necessary and should be removed from this contribution to prevent merge issues in the near future when the file is removed from the repository. Please see the referenced issue for additional information.

Upcoming Change of Git Branch Naming

Reference: #14292

Development environments will need their upstream Git branch updated from master to main in the near future. Please see the referenced issue for additional information and scheduling.

Upcoming Change of GitHub Organization

Reference: #14715

This repository will be migrating from https://github.com/terraform-providers/terraform-provider-aws to https://github.com/hashicorp/terraform-provider-aws. No practitioner or developer action is anticipated and most GitHub functionality will automatically redirect to the new location. Go import paths including terraform-providers can remain for now. Please see the referenced issue for additional information and scheduling.

[zhelding]

Pull request #21306 has significantly refactored the AWS Provider codebase. As a result, most PRs opened prior to the refactor now have merge conflicts that must be resolved before proceeding.

Specifically, PR #21306 relocated the code for all AWS resources and data sources from a single aws directory to a large number of separate directories in internal/service, each corresponding to a particular AWS service. This separation of code has also allowed for us to simplify the names of underlying functions -- while still avoiding namespace collisions.

We recognize that many pull requests have been open for some time without yet being addressed by our maintainers. Therefore, we want to make it clear that resolving these conflicts in no way affects the prioritization of a particular pull request. Once a pull request has been prioritized for review, the necessary changes will be made by a maintainer -- either directly or in collaboration with the pull request author.

For a more complete description of this refactor, including examples of how old filepaths and function names correspond to their new counterparts: please refer to issue #20000.

For a quick guide on how to amend your pull request to resolve the merge conflicts resulting from this refactor and bring it in line with our new code patterns: please refer to our Service Package Refactor Pull Request Guide.

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[github-actions]

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