Configuring an EC2 (not Fargate) instance via task_definition.json - docker

Question

Currently we have a working task_definition file for a AWS Fargate instance.
We want to migrate from Fargate to a specific AWS EC2 instance, e.g. Z1d.
From the AWS documentation I found that the ecs.instance-type parameter needs to be added.
Unfortunately it does not state where it should be added in the task_definition.json file.
Currently we have something along the lines of:
{
"family": "generic-family",
"requiresCompatibilities": ["FARGATE"],
"cpu": "4096",
"memory": "8192",
...
"containerDefinitions": [
{
"name": "generic-docker-name",
"image": "...",
},
]
}
We think it should be something like:
{
"family": "generic-family",
"requiresCompatibilities": ["EC2"],
"ecs.instance-type": "Z1d",
...
"containerDefinitions": [
{
"name": "generic-docker-name",
"image": "...",
},
]
}
Or looking at some other documentation:
{
"family": "generic-family",
"requiresCompatibilities": ["EC2"],
...
"containerDefinitions": [
{
"name": "generic-docker-name",
"image": "...",
"Parameters": {
"InstanceTypeParameter" : {
"Type" : "String",
"Default" : "z1d.large",
"AllowedValues" : ["z1d.large"],
"Description" : "..."
}
}
},
]
}
But that doesn't seem to work.
Does anyone know how this should be done? Or how I should read the AWS documentation for this specific topic?

Answer 1

Add this to your task_definition.json file at the top level.
"placementConstraints": [
{
"type": "memberOf",
"expression": "attribute:ecs.instance-type == z1d.large"
}
],
You can read more about it here: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-placement-constraints.html