EC2 Fleet – Manage Thousands of On-Demand and Spot Instances with One Request

EC2 Spot Fleets are really cool. You can launch a fleet of Spot Instances that spans EC2 instance types and Availability Zones without having to write custom code to discover capacity or monitor prices. You can set the target capacity (the size of the fleet) in units that are meaningful to your application and have Spot Fleet create and then maintain the fleet on your behalf. Our customers are creating Spot Fleets of all sizes. For example, one financial service customer runs Monte Carlo simulations across 10 different EC2 instance types. They routinely make requests for hundreds of thousands of vCPUs and count on Spot Fleet to give them access to massive amounts of capacity at the best possible price.

EC2 Fleet
Today we are extending and generalizing the set-it-and-forget-it model that we pioneered in Spot Fleet with EC2 Fleet, a new building block that gives you the ability to create fleets that are composed of a combination of EC2 On-Demand, Reserved, and Spot Instances with a single API call. You tell us what you need, capacity and instance-wise, and we’ll handle all the heavy lifting. We will launch, manage, monitor and scale instances as needed, without the need for scaffolding code.

You can specify the capacity of your fleet in terms of instances, vCPUs, or application-oriented units, and also indicate how much of the capacity should be fulfilled by Spot Instances. The application-oriented units allow you to specify the relative power of each EC2 instance type in a way that directly maps to the needs of your application. All three capacity specification options (instances, vCPUs, and application-oriented units) are known as weights.

I think you’ll find a number ways this feature makes managing a fleet of instances easier, and believe that you will also appreciate the team’s near-term feature roadmap of interest (more on that in a bit).

Using EC2 Fleet
There are a number of ways that you can use this feature, whether you’re running a stateless web service, a big data cluster or a continuous integration pipeline. Today I’m going to describe how you can use EC2 Fleet for genomic processing, but this is similar to workloads like risk analysis, log processing or image rendering. Modern DNA sequencers can produce multiple terabytes of raw data each day, to process that data into meaningful information in a timely fashion you need lots of processing power. I’ll be showing you how to deploy a “grid” of worker nodes that can quickly crunch through secondary analysis tasks in parallel.

Projects in genomics can use the elasticity EC2 provides to experiment and try out new pipelines on hundreds or even thousands of servers. With EC2 you can access as many cores as you need and only pay for what you use. Prior to today, you would need to use the RunInstances API or an Auto Scaling group for the On-Demand & Reserved Instance portion of your grid. To get the best price performance you’d also create and manage a Spot Fleet or multiple Spot Auto Scaling groups with different instance types if you wanted to add Spot Instances to turbo-boost your secondary analysis. Finally, to automate scaling decisions across multiple APIs and Auto Scaling groups you would need to write Lambda functions that periodically assess your grid’s progress & backlog, as well as current Spot prices – modifying your Auto Scaling Groups and Spot Fleets accordingly.

You can now replace all of this with a single EC2 Fleet, analyzing genomes at scale for as little as $1 per analysis. In my grid, each step in in the pipeline requires 1 vCPU and 4 GiB of memory, a perfect match for M4 and M5 instances with 4 GiB of memory per vCPU. I will create a fleet using M4 and M5 instances with weights that correspond to the number of vCPUs on each instance:

  • m4.16xlarge – 64 vCPUs, weight = 64
  • m5.24xlarge – 96 vCPUs, weight = 96

This is expressed in a template that looks like this:

"Overrides": [
{
  "InstanceType": "m4.16xlarge",
  "WeightedCapacity": 64,
},
{
  "InstanceType": "m5.24xlarge",
  "WeightedCapacity": 96,
},
]

By default, EC2 Fleet will select the most cost effective combination of instance types and Availability Zones (both specified in the template) using the current prices for the Spot Instances and public prices for the On-Demand Instances (if you specify instances for which you have matching RIs, your discounts will apply). The default mode takes weights into account to get the instances that have the lowest price per unit. So for my grid, fleet will find the instance that offers the lowest price per vCPU.

Now I can request capacity in terms of vCPUs, knowing EC2 Fleet will select the lowest cost option using only the instance types I’ve defined as acceptable. Also, I can specify how many vCPUs I want to launch using On-Demand or Reserved Instance capacity and how many vCPUs should be launched using Spot Instance capacity:

"TargetCapacitySpecification": {
	"TotalTargetCapacity": 2880,
	"OnDemandTargetCapacity": 960,
	"SpotTargetCapacity": 1920,
	"DefaultTargetCapacityType": "Spot"
}

The above means that I want a total of 2880 vCPUs, with 960 vCPUs fulfilled using On-Demand and 1920 using Spot. The On-Demand price per vCPU is lower for m5.24xlarge than the On-Demand price per vCPU for m4.16xlarge, so EC2 Fleet will launch 10 m5.24xlarge instances to fulfill 960 vCPUs. Based on current Spot pricing (again, on a per-vCPU basis), EC2 Fleet will choose to launch 30 m4.16xlarge instances or 20 m5.24xlarges, delivering 1920 vCPUs either way.

Putting it all together, I have a single file (fl1.json) that describes my fleet:

    "LaunchTemplateConfigs": [
        {
            "LaunchTemplateSpecification": {
                "LaunchTemplateId": "lt-0e8c754449b27161c",
                "Version": "1"
            }
        "Overrides": [
        {
          "InstanceType": "m4.16xlarge",
          "WeightedCapacity": 64,
        },
        {
          "InstanceType": "m5.24xlarge",
          "WeightedCapacity": 96,
        },
      ]
        }
    ],
    "TargetCapacitySpecification": {
        "TotalTargetCapacity": 2880,
        "OnDemandTargetCapacity": 960,
        "SpotTargetCapacity": 1920,
        "DefaultTargetCapacityType": "Spot"
    }
}

I can launch my fleet with a single command:

$ aws ec2 create-fleet --cli-input-json file://home/ec2-user/fl1.json
{
    "FleetId":"fleet-838cf4e5-fded-4f68-acb5-8c47ee1b248a"
}

My entire fleet is created within seconds and was built using 10 m5.24xlarge On-Demand Instances and 30 m4.16xlarge Spot Instances, since the current Spot price was 1.5¢ per vCPU for m4.16xlarge and 1.6¢ per vCPU for m5.24xlarge.

Now lets imagine my grid has crunched through its backlog and no longer needs the additional Spot Instances. I can then modify the size of my fleet by changing the target capacity in my fleet specification, like this:

{         
    "TotalTargetCapacity": 960,
}

Since 960 was equal to the amount of On-Demand vCPUs I had requested, when I describe my fleet I will see all of my capacity being delivered using On-Demand capacity:

"TargetCapacitySpecification": {
	"TotalTargetCapacity": 960,
	"OnDemandTargetCapacity": 960,
	"SpotTargetCapacity": 0,
	"DefaultTargetCapacityType": "Spot"
}

When I no longer need my fleet I can delete it and terminate the instances in it like this:

$ aws ec2 delete-fleets --fleet-id fleet-838cf4e5-fded-4f68-acb5-8c47ee1b248a 
  --terminate-instances   
{
    "UnsuccessfulFleetDletetions": [],
    "SuccessfulFleetDeletions": [
        {
            "CurrentFleetState": "deleted_terminating",
            "PreviousFleetState": "active",
            "FleetId": "fleet-838cf4e5-fded-4f68-acb5-8c47ee1b248a"
        }
    ]
}

Earlier I described how RI discounts apply when EC2 Fleet launches instances for which you have matching RIs, so you might be wondering how else RI customers benefit from EC2 Fleet. Let’s say that I own regional RIs for M4 instances. In my EC2 Fleet I would remove m5.24xlarge and specify m4.10xlarge and m4.16xlarge. Then when EC2 Fleet creates the grid, it will quickly find M4 capacity across the sizes and AZs I’ve specified, and my RI discounts apply automatically to this usage.

In the Works
We plan to connect EC2 Fleet and EC2 Auto Scaling groups. This will let you create a single fleet that mixed instance types and Spot, Reserved and On-Demand, while also taking advantage of EC2 Auto Scaling features such as health checks and lifecycle hooks. This integration will also bring EC2 Fleet functionality to services such as Amazon ECS, Amazon EKS, and AWS Batch that build on and make use of EC2 Auto Scaling for fleet management.

Available Now
You can create and make use of EC2 Fleets today in all public AWS Regions!

Jeff;


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