Container port mappings are not shown in ECS metadata response on Fargate

[hmahmood]

Summary

Not seeing the Ports field on container metadata in a response for the /task endpoint from a V4 metadata endpoint.

Description

The task definition has the portMappings field populated like so for the container:

            "portMappings": [
                {
                    "name": "nginx-80-tcp",
                    "containerPort": 80,
                    "hostPort": 80,
                    "protocol": "tcp"
                }

Expected Behavior

Observed Behavior

Environment Details

ECS Fargate

Supporting Log Snippets

[hmahmood]

Any insight into this? Is this a bug or something is missing from the task definition?

[amogh09]

Hi @hmahmood . There is no /tasks V4 metadata endpoint. Do you mean /task endpoint?

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-metadata-endpoint-v4-fargate.html

[hmahmood]

Hi @hmahmood . There is no /tasks V4 metadata endpoint. Do you mean /task endpoint?

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-metadata-endpoint-v4-fargate.html

Sorry, yes, that is what I meant.

[amogh09]

@hmahmood Port mappings are not applicable to awsvpc network mode and that's why task metadata does not include it in its response.

I see that documentation of portMappings suggests that it may be used with awsvpc network mode but in fact it's redundant.

For task definitions (both the Fargate and EC2 launch type) that use the awsvpc network mode, only specify the containerPort. The hostPort is always ignored, and the container port is automatically mapped to a random high-numbered port on the host.

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#container_definitions

[hmahmood]

Thanks @amogh09 . I also see this on the same page:

Note
After a task reaches the RUNNING status, manual and automatic host and container port assignments are visible in the following locations:

Console: The Network Bindings section of a container description for a selected task.

AWS CLI: The networkBindings section of the describe-tasks command output.

API: The DescribeTasks response.

Metadata: The task metadata endpoint.

I am not seeing the automatic port assignment from the task metadata endpoint as the blurb above claims.