Create an EC2 Fleet

To create an EC2 Fleet, define the fleet configuration in a JSON file and reference the file with the create-fleet command. In the JSON file, you must specify the total target capacity for the fleet, separate target capacities for Spot Instances and On-Demand Instances, and a launch template that defines the configuration for the instances in the fleet, such as an AMI, instance type, subnet or Availability Zone, and one or more security groups. You can optionally specify additional configurations, such as parameters to override the launch template configuration, allocation strategies for selecting Spot Instances and On-Demand Instances from the EC2 capacity pools, and the maximum amount you're willing to pay for the fleet. For more information, see Configuration options for your EC2 Fleet or Spot Fleet.

The EC2 Fleet launches On-Demand Instances when capacity is available, and launches Spot Instances when your maximum price exceeds the Spot price and capacity is available.

If your fleet includes Spot Instances and is of type maintain, Amazon EC2 will attempt to maintain your fleet target capacity when your Spot Instances are interrupted.

EC2 Fleet limitations

The following limitations apply to EC2 Fleet:

Create an EC2 Fleet

To launch a fleet of instances using EC2 Fleet, you need only specify the following parameters in your fleet request, and the fleet will use the default values for the other parameters:

To override the parameters specified in the launch template, you can specify one or more overrides. Each override can vary by instance type, Availability Zone, subnet, and maximum price, and can include a different weighted capacity. As an alternative to specifying an instance type, you can specify the attributes that an instance must have, and Amazon EC2 will identify all the instance types with those attributes. For more information, see Specify attributes for instance type selection for EC2 Fleet or Spot Fleet.

For EC2 Fleets of type instant, you can specify a Systems Manager parameter instead of the AMI ID. You can specify the Systems Manager parameter in the override or in the launch template. For more information, see Use a Systems Manager parameter instead of an AMI ID.

You can specify the fleet parameters in a JSON file. For information about all the possible parameters you can specify, see View all the EC2 Fleet configuration options.

For fleet configuration examples, see Example CLI configurations for EC2 Fleet.

There is currently no console support for creating an EC2 Fleet.

aws ec2 create-fleet --cli-input-json file://file_name.json

The following is example output for a fleet of type request or maintain.

{
    "FleetId": "fleet-12a34b55-67cd-8ef9-ba9b-9208dEXAMPLE"
} 

The following is example output for a fleet of type instant that launched the target capacity.

{
  "FleetId": "fleet-12a34b55-67cd-8ef9-ba9b-9208dEXAMPLE",
  "Errors": [],
  "Instances": [
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c5.large",
          "AvailabilityZone": "us-east-1a"
        }
      },
      "Lifecycle": "on-demand",
      "InstanceIds": [
        "i-1234567890abcdef0",
        "i-9876543210abcdef9" 
      ],
      "InstanceType": "c5.large",
      "Platform": null
    },
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c4.large",
          "AvailabilityZone": "us-east-1a"
        }
      },
      "Lifecycle": "on-demand",
      "InstanceIds": [
        "i-5678901234abcdef0",
        "i-5432109876abcdef9" 
      ]
  ]
}

The following is example output for a fleet of type instant that launched part of the target capacity with errors for instances that were not launched.

{
  "FleetId": "fleet-12a34b55-67cd-8ef9-ba9b-9208dEXAMPLE",
  "Errors": [
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c4.xlarge",
          "AvailabilityZone": "us-east-1a",
        }
      },
      "Lifecycle": "on-demand",
      "ErrorCode": "InsufficientInstanceCapacity",
      "ErrorMessage": ""
    },
  ],
  "Instances": [
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c5.large",
          "AvailabilityZone": "us-east-1a"
        }
      },
      "Lifecycle": "on-demand",
      "InstanceIds": [
        "i-1234567890abcdef0",
        "i-9876543210abcdef9" 
      ]
  ]
}

The following is example output for a fleet of type instant that launched no instances.

{
  "FleetId": "fleet-12a34b55-67cd-8ef9-ba9b-9208dEXAMPLE",
  "Errors": [
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c4.xlarge",
          "AvailabilityZone": "us-east-1a",
        }
      },
      "Lifecycle": "on-demand",
      "ErrorCode": "InsufficientCapacity",
      "ErrorMessage": ""
    },
    {
      "LaunchTemplateAndOverrides": {
        "LaunchTemplateSpecification": {
          "LaunchTemplateId": "lt-01234a567b8910abcEXAMPLE",
          "Version": "1"
        },
        "Overrides": {
          "InstanceType": "c5.large",
          "AvailabilityZone": "us-east-1a",
        }
      },
      "Lifecycle": "on-demand",
      "ErrorCode": "InsufficientCapacity",
      "ErrorMessage": ""
    },
  ],
  "Instances": []
}

Create an EC2 Fleet that replaces unhealthy Spot Instances

EC2 Fleet checks the health status of the instances in the fleet every two minutes. The health status of an instance is either healthy or unhealthy.

EC2 Fleet determines the health status of an instance by using the status checks provided by Amazon EC2. An instance is determined as unhealthy when the status of either the instance status check or the system status check is impaired for three consecutive health status checks. For more information, see Status checks for Amazon EC2 instances.

You can configure your fleet to replace unhealthy Spot Instances. After setting ReplaceUnhealthyInstances to true, a Spot Instance is replaced when it is reported as unhealthy. The fleet can go below its target capacity for up to a few minutes while an unhealthy Spot Instance is being replaced.

View all the EC2 Fleet configuration options

To view the full list of EC2 Fleet configuration parameters, you can generate a JSON file. For a description of each parameter, see create-fleet.

To generate a JSON file with all possible EC2 Fleet parameters

Use the create-fleet (AWS CLI) command and the --generate-cli-skeleton parameter to generate an EC2 Fleet JSON file, and direct the output to a file to save it.

aws ec2 create-fleet \
    --generate-cli-skeleton input > ec2createfleet.json

Example output

{
    "DryRun": true,
    "ClientToken": "",
    "SpotOptions": {
        "AllocationStrategy": "price-capacity-optimized",
        "MaintenanceStrategies": {
            "CapacityRebalance": {
                "ReplacementStrategy": "launch"
            }
        },
        "InstanceInterruptionBehavior": "hibernate",
        "InstancePoolsToUseCount": 0,
        "SingleInstanceType": true,
        "SingleAvailabilityZone": true,
        "MinTargetCapacity": 0,
        "MaxTotalPrice": ""
    },
    "OnDemandOptions": {
        "AllocationStrategy": "prioritized",
        "CapacityReservationOptions": {
            "UsageStrategy": "use-capacity-reservations-first"
        },
        "SingleInstanceType": true,
        "SingleAvailabilityZone": true,
        "MinTargetCapacity": 0,
        "MaxTotalPrice": ""
    },
    "ExcessCapacityTerminationPolicy": "termination",
    "LaunchTemplateConfigs": [
        {
            "LaunchTemplateSpecification": {
                "LaunchTemplateId": "",
                "LaunchTemplateName": "",
                "Version": ""
            },
            "Overrides": [
                {
                    "InstanceType": "r5.metal",
                    "MaxPrice": "",
                    "SubnetId": "",
                    "AvailabilityZone": "",
                    "WeightedCapacity": 0.0,
                    "Priority": 0.0,
                    "Placement": {
                        "AvailabilityZone": "",
                        "Affinity": "",
                        "GroupName": "",
                        "PartitionNumber": 0,
                        "HostId": "",
                        "Tenancy": "dedicated",
                        "SpreadDomain": "",
                        "HostResourceGroupArn": ""
                    },
                    "InstanceRequirements": {
                        "VCpuCount": {
                            "Min": 0,
                            "Max": 0
                        },
                        "MemoryMiB": {
                            "Min": 0,
                            "Max": 0
                        },
                        "CpuManufacturers": [
                            "amd"
                        ],
                        "MemoryGiBPerVCpu": {
                            "Min": 0.0,
                            "Max": 0.0
                        },
                        "ExcludedInstanceTypes": [
                            ""
                        ],
                        "InstanceGenerations": [
                            "previous"
                        ],
                        "SpotMaxPricePercentageOverLowestPrice": 0,
                        "OnDemandMaxPricePercentageOverLowestPrice": 0,
                        "BareMetal": "included",
                        "BurstablePerformance": "required",
                        "RequireHibernateSupport": true,
                        "NetworkInterfaceCount": {
                            "Min": 0,
                            "Max": 0
                        },
                        "LocalStorage": "excluded",
                        "LocalStorageTypes": [
                            "ssd"
                        ],
                        "TotalLocalStorageGB": {
                            "Min": 0.0,
                            "Max": 0.0
                        },
                        "BaselineEbsBandwidthMbps": {
                            "Min": 0,
                            "Max": 0
                        },
                        "AcceleratorTypes": [
                            "inference"
                        ],
                        "AcceleratorCount": {
                            "Min": 0,
                            "Max": 0
                        },
                        "AcceleratorManufacturers": [
                            "amd"
                        ],
                        "AcceleratorNames": [
                            "a100"
                        ],
                        "AcceleratorTotalMemoryMiB": {
                            "Min": 0,
                            "Max": 0
                        }
                    }
                }
            ]
        }
    ],
    "TargetCapacitySpecification": {
        "TotalTargetCapacity": 0,
        "OnDemandTargetCapacity": 0,
        "SpotTargetCapacity": 0,
        "DefaultTargetCapacityType": "on-demand",
        "TargetCapacityUnitType": "memory-mib"
    },
    "TerminateInstancesWithExpiration": true,
    "Type": "instant",
    "ValidFrom": "1970-01-01T00:00:00",
    "ValidUntil": "1970-01-01T00:00:00",
    "ReplaceUnhealthyInstances": true,
    "TagSpecifications": [
        {
            "ResourceType": "fleet",
            "Tags": [
                {
                    "Key": "",
                    "Value": ""
                }
            ]
        }
    ],
    "Context": ""
}