For more information about the Amazon ECS cluster, run the following command. You will find the number of running tasks, capacity providers, and more. 

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aws ecs describe-clusters --cluster <your-fargate-cluster>

Sample output:

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{
    "clusters": [
        {
            "clusterArn": "arn:aws:ecs:us-east-2:123456789012:cluster/<your-fargate-cluster>",
            "clusterName": "fargate-getting-started",
            "status": "ACTIVE",
            "registeredContainerInstancesCount": 0,
            "runningTasksCount": 3,
            "pendingTasksCount": 0,
            "activeServicesCount": 1,
            "statistics": [],
            "tags": [],
            "settings": [],
            "capacityProviders": [
                "FARGATE",
                "FARGATE_SPOT"
            ],
            "defaultCapacityProviderStrategy": []
        }
    ],
    "failures": []
}