Fix: Step Functions Batch SubmitJob & ECS Container Issue

Introduction

This article addresses a critical issue encountered when using AWS Step Functions to manage AWS Batch jobs, specifically when dealing with ECS multi-container Batch setups. The problem arises when Step Functions' BatchSubmitJob task automatically adds ContainerOverrides, which are incompatible with Batch jobs that utilize ecsProperties. This leads to job submission failures and disrupts the intended workflow. We will explore the details of this bug, its impact, and potential solutions. If you're leveraging AWS Batch and Step Functions for orchestrating your containerized workloads, understanding this issue is crucial for ensuring smooth and reliable execution.

Understanding the Bug: Incompatibility of Container Overrides with ECS Properties

The core of the issue lies in the conflict between AWS Step Functions' default behavior and the requirements of AWS Batch jobs configured with ecsProperties. When a job definition in AWS Batch is set up to run multiple containers within a single task using ecsProperties, it expects to manage container configurations directly. However, the BatchSubmitJob task in Step Functions, by default, injects a ContainerOverrides section into the job definition during submission. This ContainerOverrides section typically includes environment variables like MANAGED_BY_AWS: STARTED_BY_STEP_FUNCTIONS. While this is generally helpful for tracking jobs initiated by Step Functions, it becomes problematic when ecsProperties are involved.

The AWS Batch service throws an error when it encounters ContainerOverrides in a job definition that also uses ecsProperties. This is because the service expects container configurations to be exclusively managed within the ecsProperties block for multi-container jobs. The presence of ContainerOverrides creates ambiguity and leads to the following error message: Container overrides should not be set for ecsProperties jobs. (Service: AWSBatch; Status Code: 400; Error Code: ClientException; Request ID: [unique-request-id]; Proxy: null). This error effectively prevents the Step Function from successfully launching the Batch job, disrupting the intended workflow.

To further clarify, consider a scenario where you have defined a Batch job definition with two containers, each with specific resource requirements and configurations, within the ecsProperties. You intend to use Step Functions to orchestrate the execution of this job as part of a larger workflow. When Step Functions' BatchSubmitJob task attempts to submit the job, it inadvertently adds the ContainerOverrides, triggering the error and halting the process. This incompatibility highlights a critical gap in the integration between Step Functions and Batch when dealing with multi-container setups.

Real-World Impact and Examples

The ramifications of this bug can be significant for organizations relying on AWS Batch and Step Functions for their containerized workloads. Imagine a data processing pipeline where multiple containers need to collaborate on a single dataset. This is a common use case for ecsProperties, allowing you to define containers that share resources and communicate efficiently. If Step Functions is used to manage this pipeline, the ContainerOverrides issue can break the entire workflow, leading to processing delays and potential data loss.

Consider a specific example of an image processing application. You might have one container responsible for downloading images from a source, another for performing image manipulation, and a third for uploading the processed images to a storage service. All these containers are defined within the ecsProperties of a single Batch job definition. If Step Functions is used to trigger this job, the ContainerOverrides conflict will prevent the job from running, effectively halting the image processing pipeline.

Another use case could involve machine learning workflows, where different containers might be responsible for data preprocessing, model training, and evaluation. Using ecsProperties allows you to optimize resource utilization by running these tasks concurrently within a single Batch job. However, the ContainerOverrides issue can severely impact the reliability of these workflows, hindering the development and deployment of machine learning models.

The impact extends beyond immediate job failures. Debugging this issue can be time-consuming, as the error message might not immediately point to the ContainerOverrides conflict. Developers might spend valuable time investigating other potential causes before discovering the root problem. This delay can further exacerbate the disruption to critical workflows and impact overall productivity.

Code Example and Error Reproduction

To illustrate the issue, let's examine a simplified code example using the AWS Cloud Development Kit (CDK) in TypeScript. This example demonstrates how to define a Batch job definition with ecsProperties and then attempt to launch it using Step Functions' BatchSubmitJob task.

First, define a Batch job definition with two containers within ecsProperties:

import * as cdk from 'aws-cdk-lib';
import * as batch from 'aws-cdk-lib/aws-batch';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as ecs from 'aws-cdk-lib/aws-ecs';
import { Construct } from 'constructs';

class BatchJobDefinitionStack extends cdk.Stack {
 constructor(scope: Construct, id: string, props?: cdk.StackProps) {
 super(scope, id, props);

 const vpc = new ec2.Vpc(this, 'Vpc', { maxAzs: 2 });

 const cluster = new ecs.Cluster(this, 'EcsCluster', { vpc });

 const jobDefinition = new batch.CfnJobDefinition(this, 'MyJobDefinition', {
 type: 'container',
 platformCapabilities: ['EC2'],
 containerProperties: {
 image: 'public.ecr.aws/amazonlinux/amazonlinux2023:latest',
 jobRoleArn: 'arn:aws:iam::123456789012:role/ecsTaskExecutionRole',
 resourceRequirements: [
 { type: 'VCPU', value: '1' },
 { type: 'MEMORY', value: '2048' },
 ],
 ecsProperties: {
 containers: [
 {
 name: 'container1',
 image: 'public.ecr.aws/amazonlinux/amazonlinux2023:latest',
 resourceRequirements: [
 { type: 'VCPU', value: '0.5' },
 { type: 'MEMORY', value: '1024' },
 ],
 },
 {
 name: 'container2',
 image: 'public.ecr.aws/amazonlinux/amazonlinux2023:latest',
 resourceRequirements: [
 { type: 'VCPU', value: '0.5' },
 { type: 'MEMORY', value: '1024' },
 ],
 },
 ],
 },
 });
 }
}

Next, try to launch this job definition using Step Functions:

import * as sfn from 'aws-cdk-lib/aws-stepfunctions';
import * as tasks from 'aws-cdk-lib/aws-stepfunctions-tasks';

class StepFunctionStack extends cdk.Stack {
 constructor(scope: Construct, id: string, props?: cdk.StackProps) {
 super(scope, id, props);

 const jobDefinitionArn = 'arn:aws:batch:us-east-1:123456789012:job-definition/MyJobDefinition'; // Replace with your Job Definition ARN
 const jobQueueArn = 'arn:aws:batch:us-east-1:123456789012:job-queue/MyJobQueue'; // Replace with your Job Queue ARN

 const batchJobTask = new tasks.BatchSubmitJob(this, 'BatchSubmitJobTask', {
 jobName: 'MyBatchJob',
 jobDefinitionArn: jobDefinitionArn,
 jobQueueArn: jobQueueArn,
 });

 const definition = new sfn.Chain(batchJobTask);

 new sfn.StateMachine(this, 'MyStateMachine', {
 definition,
 });
 }
}

When you execute this Step Function, the BatchSubmitJob task will fail with the error: Container overrides should not be set for ecsProperties jobs. This clearly demonstrates the incompatibility issue.

Potential Solutions and Workarounds

Several approaches can be considered to address this issue. One potential solution is for AWS to update the BatchSubmitJob task in Step Functions to conditionally include ContainerOverrides based on the job definition configuration. If a job definition uses ecsProperties, the task should avoid adding ContainerOverrides to prevent the conflict.

In the meantime, several workarounds can be employed. One option is to modify the job definition to avoid using ecsProperties altogether. This might involve restructuring the application to run each container as a separate Batch job, which can add complexity and overhead. Another workaround is to use a Lambda function as an intermediary to submit the Batch job. The Lambda function can programmatically submit the job without adding the ContainerOverrides. This approach provides more control but introduces an additional component into the workflow.

Another potential workaround involves leveraging the AWS SDK directly within a Step Functions' Task state, utilizing a Lambda Function. This approach grants you fine-grained control over the job submission process, enabling you to construct the Batch submission request without the problematic ContainerOverrides. While effective, this method requires a deeper understanding of the AWS SDK and adds complexity to your Step Function definition.

Community Discussion and Related Issues

This issue has been reported by multiple users in the AWS community, highlighting its widespread impact. A related discussion on the AWS re:Post forums (https://repost.aws/questions/QUYUtrKcPGRf-Rj1m1dXJH1Q/aws-batch-running-ecsproperties-job-with-aws-stepfunction) provides further context and insights into the problem. This underscores the need for a comprehensive solution to ensure seamless integration between Step Functions and Batch for multi-container workloads.

Conclusion

The incompatibility between Step Functions' BatchSubmitJob task and AWS Batch jobs with ecsProperties is a significant issue that can disrupt containerized workflows. The automatic addition of ContainerOverrides by Step Functions conflicts with the requirements of multi-container Batch jobs, leading to job submission failures. While workarounds exist, a long-term solution from AWS is necessary to address this problem effectively. Understanding this issue and its potential impact is crucial for organizations leveraging AWS Batch and Step Functions for their container orchestration needs. By staying informed and employing appropriate workarounds, you can mitigate the risks and ensure the reliability of your workflows. For further reading on AWS Step Functions and its integration with other services, you might find the official AWS Step Functions documentation here to be a valuable resource. 📝