Beginning on January 6th, Amazon Web Services added a new option to include your instance’s tags as part of the instance’s metadata when the instance is launched:

https://aws.amazon.com/about-aws/whats-new/2022/01/instance-tags-amazon-ec2-instance-metadata-service/

By including this data in the instance metadata, this information no longer needs the DescribeInstances or DescribeTags API calls to retrieve tag information. For shops which use tag information extensively, this will cut down on the number of API calls you need to make and allow tag retrieval to scale better.

There is one limitation: tags stored in metadata cannot have spaces. If you have the “tags in metadata” option enabled and you have a tag with spaces in it, you’ll see a message similar to the one below:

‘Tag Name Here’ is not a valid tag key. Tag keys must match pattern ([0-9a-zA-Z-_+=,[email protected]:]{1,255}), and must not be a reserved name (‘.’, ‘..’, ‘_index’)

This was an issue for me yesterday because I’m using AWS’s Patch Manager to keep my instances updated and that uses the following tag:

Patch Group

This tag must be used by patching groups and is referenced in the documentation this way:

Patch groups require use of the tag key Patch Group. You can specify any tag value, but the tag key must be Patch Group.

https://docs.aws.amazon.com/systems-manager/latest/userguide/sysman-patch-group-tagging.html

The result was that I set up a new instance yesterday with my tags, including the Patch Group tag, and received the following message when I tried to launch the instance:

‘Patch Group’ is not a valid tag key. Tag keys must match pattern ([0-9a-zA-Z-_+=,[email protected]:]{1,255}), and must not be a reserved name (‘.’, ‘..’, ‘_index’)

I put in a ticket to AWS Support and the fix is the following:

When setting up new EC2 instances, make sure that the Allow tags in metadata setting under the Advanced Details section is set to Disabled.

This turns off including your instance’s tags as part of the instance’s metadata as part of the instance’s launch. This addresses the issue because tag information will not be added to your instance’s metadata and thus removes the metadata tagging limitations from the instance creation process. Now your tags can include spaces again, though you’re also back to having to retrieve tag information via the API.

On Monday, January 10th 2022, the Allow tags in metadata setting was set to Enabled by default. However, I suspect AWS got enough support calls about this particular issue that they made a change to the default settings. As of Tuesday, January 11th 2022, the Allow tags in metadata setting is now set to Disabled by default.