Detect AWS Region using the metadata service

[Tieske]

continuation of Kong/kong-plugin-aws-lambda#56

[Tieske]

In addition to the info in the original PR, there's also some pointers here; in the Java sdk; https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/region-selection.html#automatically-determine-the-aws-region-from-the-environment

[Tieske]

Try logic (updated from the old issue):

• read AWS_REGION environment variable (std across AWS cli apparently)
• read AWS_DEFAULT_REGION environment variable (std across AWS cli apparently)
• scan for ECS_CONTAINERMETADATA_URI_V4 or ECS_CONTAINERMETADATA_URI environment variables
• if found request and get AvailabilityZone --> seems to be ECS (we're skipping the V2 on ECS, which seems valid since its outdated)
• else try IMDSv2 (risks blocking) --> assumes it to be EC2, use short timeout, eg. 5 seconds
• requests should be within a lock to prevent many simultaneously
• the actual requests should be made a run-time, not during start up, because during startup we do not even know whether we're running on AWS infra or even if we need the region info, and then we'd possibly incur the penalty of the blocking requests until a timeout

Option would be to implement the first two above first, and the remainder later.

[Tieske]

@bungle here's my implementation in the AWS SDK: Kong/lua-resty-aws#9

[gszr]

@bungle @Tieske What specific bits aren't covered by #7765?

[Tieske]

the env var is only one options whilst there are many more. Any way AWS has no supported way of detecting it.

The AWS Lambda plugin should be rewritten on top of the aws-sdk, that would solve the issue.

[gszr]

The AWS Lambda plugin should be rewritten on top of the aws-sdk, that would solve the issue.

@Tieske Are we keeping track of this task somewhere? Thanks for explaining!

[Tieske]

internally FTI-4296