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Optimizing Amazon EMR for resilience and cost with capacity-optimized Spot Instances
Amazon EMR now supports the capacity-optimized allocation strategy for Amazon Elastic Compute Cloud (Amazon EC2) Spot Instances for launching Spot Instances from the most available Spot Instance capacity pools by analyzing capacity metrics in real time. You can now specify up to 15 instance types in your EMR task instance fleet configuration. This provides Amazon EMR with more options in choosing the optimal pools to launch Spot Instances from in order to decrease chances of Spot interruptions, and increases the ability to relaunch capacity using other instance types in case Spot Instances are interrupted when Amazon EC2 needs the capacity back.
Background
Amazon EMR is the industry-leading cloud big data platform for processing vast amounts of data using open-source tools such as Apache Spark, Apache Hive, Apache HBase, Apache Flink, Apache Hudi, and Presto. With Amazon EMR, you can run petabyte-scale analysis at less than half of the cost of traditional on-premises solutions, and over three times as fast on Amazon EMR runtime for Apache Spark compared to running without the runtime. If you have existing on-premises deployments of open-source tools such as Apache Spark and Apache Hive, you can also run Amazon EMR clusters on AWS Outposts.
Spot Instances are spare Amazon EC2 compute capacity in the AWS Cloud available to you at savings of up to 90% compared to On-Demand Instance prices. The only difference between On-Demand Instances and Spot Instances is that Amazon EC2 can interrupt Spot Instances with 2 minutes of notification when Amazon EC2 needs the capacity back. Using Spot Instances in Amazon EMR is a common pattern that allows AWS customers to achieve significant cost savings.
The capacity-optimized allocation strategy in the Amazon EC2 fleet (also available for Amazon EC2 Auto Scaling and Spot Fleet) provisions Spot Instances from the most-available Spot Instance pools by analyzing capacity metrics. By offering the possibility of fewer interruptions, the capacity-optimized strategy can lower the overall cost of your workload. For more information about how AWS customers are benefiting from decreased Spot interruptions with the capacity-optimized allocation strategy, see Capacity-Optimized Spot Instance Allocation in Action at Mobileye and Skyscanner.
Amazon EMR uses the Amazon EC2 RunInstances API to provision compute capacity. We are enhancing the way Amazon EMR provisions EC2 instances to provide more flexibility and increased cluster resilience using EC2 Fleet (CreateFleet) in Instant mode, as a drop-in replacement for RunInstances.
Optimizing capacity for greater resilience
With this launch, you can configure Amazon EMR to use allocation strategies.
The capacity-optimized allocation strategy uses real-time capacity data to allocate instances from the Spot Instance pools with the optimal capacity for the number of instances that are launching. This allocation strategy is appropriate for workloads that have a higher cost of interruption. Examples include long-running jobs and multi-tenant persistent clusters running Apache Spark, Apache Hive, and Presto. This allocation strategy lets you specify up to 15 EC2 instance types on task instance fleets to diversify your Spot requests and get steep discounts. Previously, instance fleets allowed a maximum of five instance types. You can now diversify your Spot requests across these 15 pools within each Availability Zone and prioritize deploying into a deeper capacity pool to lower the chance of interruptions. With more instance type diversification, Amazon EMR has more capacity pools to allocate capacity from, and chooses the Spot Instances which are least likely to be interrupted.
For example, if you’re initially using EC2 memory-optimized r5.4xlarge instances (with 16 vCPUs and 128GB of RAM) for your EMR task nodes, you can configure the EMR task instance fleet with different instances types. First, explore different-sized instance types such as r5.2xlarge and r5.8xlarge. Second, add previous generation r4.4xlarge and other R4 instance sizes. After you’ve added different sizes within the same family, as well as previous generation instance types, you can add extra instance types with similar hardware characteristics and vCPU to memory ratio, such as the r5a instance family with AMD processors, r5d instance family with locally attached NVMe storage, and more.
The allocation strategy is also taken into account in case the cluster scales out after the initial provisioning phase—for example, if you manually resize the core or task fleets, or if you’re using managed scaling to automatically increase or decrease the number of instances or units in your cluster based on workload.
For more information about Spot Instance configuration if you’re using Amazon EMR to run Apache Spark workloads, see Best practices for running Apache Spark applications using Amazon EC2 Spot Instances with Amazon EMR. This blog emphasizes best practices that will help you build your Spark workloads with Amazon EMR to achieve deep cost savings.
Amazon EMR has made significant enhancements to improve elasticity and resilience, including graceful decommissioning of Spot Instances running Apache Spark and Apache Hadoop applications. Amazon EMR has customizations to open-source Apache Spark that make it more resilient to node loss—integrating with YARN’s decommissioning mechanism, extending Apache Spark’s blacklisting mechanism and actions on decommissioned nodes.
For example, when Spot Instances are interrupted in a running EMR cluster, stage failures don’t count towards the total number of failures that trigger a total job failure. For more information, see Spark enhancements for elasticity and resilience on Amazon EMR.
New configuration options and IAM policy requirements
To leverage the allocation strategies in your EMR clusters, you need to use a new AllocationStrategy parameter in your cluster configurations. Amazon EMR added support for an On-Demand allocation strategy: you can specify multiple On-Demand Instance types in your core or task instance fleets, and specify an allocation strategy of “lowest-price” to have Amazon EMR provision On-Demand Instances that have the lowest costs. This allows you to also be flexible with your selection of On-Demand instance types.
The following is an example snippet from an Amazon EMR JSON configuration file with the new capabilities:
For more information about the API options, see InstanceFleetProvisioningSpecifications.
The following IAM policy shows the additional service role permissions required to create a cluster that uses the instance fleet allocation strategy option. If your clusters are using the default role EMR_DefaultRole (which has the default managed policy attached AmazonElasticMapReduceRole), the managed policy is already updated to include these new role permissions. If your clusters are using a different role or policy, make sure you add these new permissions to your policy. See the following IAM policy:
Launching an EMR cluster with capacity-optimized Spot Instances and a diversified task fleet
In this section, we look at how to create an EMR cluster that includes allocation strategy configurations and a diversified task fleet. The reason for specifying more instance types is in order to allow Amazon EMR to launch instances from the most optimal capacity pools, and be able to replenish the cluster’s target capacity in case Spot Instances are interrupted. Moreover, by using the capacity-optimized allocation strategy, Spot Instances will be launched from the most available capacity pools, effectively decreasing the chances of Spot interruptions.
The following AWS Command Line Interface (AWS CLI) command launches an EMR cluster in the default AWS Region configured in your AWS CLI configuration, with the master and core nodes running on On-Demand Instances, and a task fleet running Spot Instances.
Amazon EMR uses a wide selection of instance types in the task instance fleet and uses "AllocationStrategy": "CAPACITY_OPTIMIZED" to launch instances from the most available Spot capacity pools and decrease the chances of workload interruptions. By providing a WeightedCapacity for each instance type that is equal to the number of vCPU (or YARN vCores), you can specify a TargetSpotCapacity that defines the number of vCPUs (YARN vCores) in your task fleet and be flexible around the instance sizes, effectively providing more capacity pools to choose from. You should specify a subnet ID per Availability Zone in the AWS Region. While each EMR cluster runs in a single Availability Zone, specifying multiple Availability Zones allows you to architect your workload with increased fault-tolerance.
See the following AWS CLI command for an example of launching an Amazon EMR cluster that adheres to the recommendations in this blog post (uses Allocation Strategies and a diversified set of instance types in the task fleet):
The following screenshot shows the result on the Amazon EMR console.
Conclusion
With this new functionality in Amazon EMR, you can increase the resilience of your organization’s data-processing workloads and optimize your costs by using Spot Instances. The capacity-optimized allocation strategy works to decrease the possibility of Spot interruptions in your cluster and allows you to specify up to 15 different instance types for your task fleet, enabling Amazon EMR to find the most available Spot capacity pools for your workload. With the Amazon EMR enhancements for increased resilience and the capacity-optimized allocation strategy for Spot Instances, you can achieve deep cost savings without compromising on availability.
About the authors
Ran Sheinberg is a principal solutions architect in the EC2 Spot team with Amazon Web Services. He works with AWS customers on cost optimizing their compute spend by utilizing Spot Instances across different types of workloads: stateless web applications, queue workers, containerized workloads, analytics, HPC and others.