Terraform multiple volumes in ECS task definition JSON

Question

I want to add multiple volume defintions in my ECS task definition JSON like this:

[
{
    "name": "agent",
    "image": "${agent_image}",
    "essential": true,
    "environment": [
        {
            "name": "apple",
            "value": "mango"
        },
        {
            "name": "AGENT_NAME",
            "value": "AGENT3"
        }
    ],
    "volume": {
        "name"      : "/data/agent2/conf",
        "host_path" : "/data/agent2/conf"
    }
    "volume": {
        "name"      : "/data/agent3/conf",
        "host_path" : "/data/agent3/conf"
    }
    
}
]

This is obviously not working because json cannot have 2 keys volume with the same name. How to acheive this? Please help.

Answer 1

I don't know exactly what you are trying to achieve, but let me try to help with a few ideas:

The following will map the /data/agent3/conf to the /data/agent/conf inside your container:

{
    "containerDefinitions": [
        {
            "mountPoints": [
                {
                    "containerPath": "/data/agent/conf",
                    "sourceVolume": "vol1"
                }
            ]
        }
    ],
    "volumes": [
        {
            "name": "vol1",
            "host": {
                "sourcePath": "/data/agent3/conf"
              }
        }
    ]
}

If you want to use two volumes:

{
    "containerDefinitions": [
        {
            "mountPoints": [
                {
                    "containerPath": "/data/agent/conf",
                    "sourceVolume": "vol1"
                },
                {
                    "containerPath": "/alternate/path/to/conf",
                    "sourceVolume": "vol2"
                }
            ]
        }
    ],
    "volumes": [
        {
            "name": "vol1",
            "host": {
                "sourcePath": "/data/agent3/conf"
              }
        },
        {
            "name": "vol2",
            "host": {
                "sourcePath": "/data/agent3/conf"
              }
        }
    ]
}

As far as I know, It's not possible to mount two volumes into the same mount point within your container. :)

But if you're trying to share data between containers/tasks between multiple hosts, Amazon EFS will be a better option.

You can find more details bellow:

Amazon ECS and Docker volume drivers

Bind Mounts