Move v2 metadata models to ecs-agent module

[amogh09]

Summary

Move v2 metadata models to ecs-agent module. These models will be needed in ecs-agent module in future work when we move metadata endpoint handlers to ecs-agent module.

Implementation details

• Move TaskResponse, ContainerResponse, LimitsResponse, and ErrorResponse structs from agent/handlers/v2/response.go to ecs-agent/tmds/handlers/v2/response.go.
• Add a new struct HealthStatus for metadata health status that replaces apicontainer.HealthStatus from agent/api/container package in ContainerResponse. This is done to decouple metadata health status from API Container health status that is used in a lot of places. The new struct has the same fields except for Status field that has type string instead of ContainerHealthStatus enum.
• A new dockerContainerHealthToV2Health function is added to agent/handlers/v2/response.go that converts apicontainer.HealthStatus to metadata HealthStatus. TestDockerContainerHealthToV2HealthJSON is added to ensure that the JSON representations of the two structs is the same.
• Existing unit tests in agent/handlers/v2/response_test.go are updated with new asserts for health status for greater confidence in the new health status struct.

Testing

New unit tests are added for the new health status struct.

In addition to automated tests, also performed manual tests to ensure that the v2, v3, and v4 metadata endpoints return the same metadata with and without the changes in this PR.

New tests cover the changes: yes

Description for the changelog

Move v2 metadata models to ecs-agent module

Licensing

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

[amogh09]

This is a new type which matches the apicontainer.HealthStatus type that is being used in v2 metadata response currently.

amazon-ecs-agent/agent/api/container/container.go

Lines 111 to 120 in 883211e

	type HealthStatus struct {
	// Status is the container health status
	Status apicontainerstatus.ContainerHealthStatus `json:"status,omitempty"`
	// Since is the timestamp when container health status changed
	Since *time.Time `json:"statusSince,omitempty"`
	// ExitCode is the exitcode of health check if failed
	ExitCode int `json:"exitCode,omitempty"`
	// Output is the output of health check
	Output string `json:"output,omitempty"`
	}

This is being done to decouple metadata response models from API models.

[chienhanlin]

Q. did we previously send heath status ContainerHealthUnknown? If yes, would this be a new change introduced to v2? Also curious how would Since, ExitCode and Output look like when status is ContainerHealthUnknown : )

[amogh09]

That's a good question. No we do not send Status when container's health status is ContainerHealthUnknown because the Status field in apicontainer.HealthStatus struct is defined with json:"status,omitempty".

ContainerHealthUnknown is the zero value of Status's type so Status = ContainerHealthUnknown is skipped when apicontainer.HealthStatus is marshaled to JSON.

The TestDockerContainerHealthToV2HealthJSON test in this PR covers this case.

amazon-ecs-agent/agent/api/container/container.go

Lines 111 to 120 in 883211e

	type HealthStatus struct {
	// Status is the container health status
	Status apicontainerstatus.ContainerHealthStatus `json:"status,omitempty"`
	// Since is the timestamp when container health status changed
	Since *time.Time `json:"statusSince,omitempty"`
	// ExitCode is the exitcode of health check if failed
	ExitCode int `json:"exitCode,omitempty"`
	// Output is the output of health check
	Output string `json:"output,omitempty"`
	}

amazon-ecs-agent/agent/api/container/status/containerstatus.go

Lines 43 to 50 in 883211e

	const (
	// ContainerHealthUnknown is the initial status of container health
	ContainerHealthUnknown ContainerHealthStatus = iota
	// ContainerHealthy represents the status of container health check when returned healthy
	ContainerHealthy
	// ContainerUnhealthy represents the status of container health check when returned unhealthy
	ContainerUnhealthy
	)

[chienhanlin]

Thanks for explaining this in detail!