Improve error log when instance reigstration fails due to bad attributes

[angelcar]

Summary

Addresses #2981

Implementation details

The validation of the attributes is done in the back-end. When validation fails, the back end doesn't return an actual error, so the agent actually compares attributes in the request vs attributes in the response, and if any are missing we deduct there was a problem, how ever there's no information as to why.

However, the information about attribute validation is documented publicly, so we add that information in the log for the customer convenience.

Testing

UTs suffice

Description for the changelog

• Improvement of log message displayed when container instance registartion fails due to attribute validation errors.

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[yinyic]

agent actually compares attributes in the request vs attributes in the response, and if any are missing we deduct there was a problem

Is it possible to include the attributes that fail to register in the error message? I think that'll give customer a better clue.

[angelcar]

Is it possible to include the attributes that fail to register in the error message? I think that'll give customer a better clue.

Good idea @yinyic . Will do

Actually @yinyic, that log message already exists here:

amazon-ecs-agent/agent/api/ecsclient/client.go

Line 324 in 20fdeeb

seelog.Errorf("Error registering attributes: %v", msg)