Nope, You Can't Run a Windows Service in ECS Fargate Using LocalStack. A Developer's Reality Check

Nope, You Can't Run a Windows Service in ECS Fargate Using LocalStack? A Developer's Reality Check

Aaron Rose   

Software Engineer & Technology Writer

Problem

You've got a Windows service running in a Docker container. It's deployed to ECS Fargate and processes messages from an SQS queue. Now you want to streamline your development workflow by simulating everything locally. LocalStack sounds like the perfect tool—but can it really handle a Windows service deployed to Fargate?

Clarifying the Issue

At first glance, the setup seems straightforward. LocalStack emulates AWS services locally. ECS? Supported. Fargate? Supported. SQS? Definitely supported. But when you dig deeper into the platform requirements, the picture becomes clearer—and more restrictive.

LocalStack's ECS simulation is built on top of Docker's Linux container engine. There's no support for Docker's Windows container mode, which means you can't run Windows-based container images in LocalStack's ECS environment. When you attempt to deploy a Windows container task, you'll either see explicit failures during task startup or the task will appear to launch but never actually execute your Windows service code.

This creates a fundamental incompatibility: your production workload runs on Windows containers in AWS Fargate, but LocalStack can only simulate Linux-based ECS tasks.

Why It Matters

If you're working in a Windows ecosystem—legacy services, background workers, or .NET Framework applications—this limitation significantly impacts your development workflow. Many enterprises are containerizing existing Windows services as part of their cloud migration journey.

Local emulation shortens development cycles, reduces cloud costs, and increases deployment confidence. When LocalStack can't run your actual Windows container, you're forced to test infrastructure configuration separately from service behavior, or find creative workarounds.

Being able to validate the complete system locally—infrastructure and runtime behavior—is crucial for maintaining development velocity and catching integration issues early.

Key Terms

• ECS Fargate: AWS's serverless container platform that abstracts away server management
• Windows Container: Docker container running Windows-based applications, requiring Windows host compatibility
• LocalStack: Local AWS service emulator, primarily designed for Linux-based development workflows
• SQS: AWS's managed message queue service for asynchronous task processing
• Task Definition: ECS configuration specifying container image, resources, and runtime requirements

Steps at a Glance

1. Deploy supporting AWS infrastructure (SQS, IAM roles) using LocalStack
2. Attempt Windows container deployment to confirm the limitation
3. Point your Windows service to LocalStack's SQS endpoint for integration testing
4. Run the Windows service locally outside of containers
5. Optionally create a Linux shim container for ECS simulation
6. Use the shim for infrastructure testing in LocalStack
7. Deploy the real Windows container to AWS for staging and production

Detailed Steps

Your goal is to test as much as possible locally while working within LocalStack's platform constraints. Focus on separating infrastructure validation from service logic testing.


Step 1: Create supporting AWS infrastructure in LocalStack

Use Terraform, CDK, or AWS CLI to provision your SQS queues, ECS task definitions, and IAM roles. All supporting infrastructure works perfectly in LocalStack—the limitation is specifically with Windows container execution.


Step 2: Verify the Windows container limitation

Deploy your Windows-based ECS task definition to LocalStack as a sanity check. This will fail or appear to succeed while never actually running your service code. It's worth confirming this limitation with your team, but it's not a viable execution path.


Step 3: Configure SQS integration for local testing

Point your Windows service directly to LocalStack's SQS endpoint. This validates your complete message processing logic without requiring containerization. 

c#

// Configure .NET service to use LocalStack SQS
var config = new AmazonSQSConfig
{
    ServiceURL = "http://localhost:4566", // LocalStack's default port
    UseHttp = true,
    AuthenticationRegion = "us-east-1"
};

var sqsClient = new AmazonSQSClient("test", "test", config);

Step 4: Run the Windows service locally

Execute your service directly on your Windows development machine while connected to LocalStack's SQS. This tests end-to-end functionality: message receiving, processing, error handling, and queue cleanup.


Step 5: Build a Linux simulation container (optional)

Create a lightweight Linux container that mimics your Windows service's message processing behavior. This enables ECS task testing within LocalStack, even with simplified business logic. 

python

import boto3
import time
import json

# Connect to LocalStack SQS
sqs = boto3.client(
    'sqs',
    endpoint_url='http://localhost:4566',
    region_name='us-east-1',
    aws_access_key_id='test',
    aws_secret_access_key='test'
)

queue_url = sqs.get_queue_url(QueueName='my-processing-queue')['QueueUrl']

# Simulate message processing loop
while True:
    try:
        response = sqs.receive_message(QueueUrl=queue_url, MaxNumberOfMessages=1)
        
        for message in response.get('Messages', []):
            print(f"Processing message: {message['Body']}")
            # Simulate your Windows service logic here
            
            # Delete message after successful processing
            sqs.delete_message(
                QueueUrl=queue_url,
                ReceiptHandle=message['ReceiptHandle']
            )
            
    except Exception as e:
        print(f"Error processing messages: {e}")
        
    time.sleep(5)  # Polling interval

Step 6: Use the shim for ECS infrastructure testing

Deploy the Linux simulation container to LocalStack's ECS to validate task definitions, service auto-scaling, networking configuration, and deployment workflows. This tests everything except the actual Windows service execution.


Step 7: Deploy the real Windows container to AWS

For staging and production environments, deploy your actual Windows container to ECS Fargate. Ensure your task definition specifies operatingSystemFamily: WINDOWS_SERVER_2019_CORE and uses platform version 1.0.0 or higher.

Conclusion

You cannot run Windows containers in LocalStack's ECS Fargate simulation due to fundamental Docker platform limitations. LocalStack's container orchestration relies on Linux-based Docker execution, which is incompatible with Windows container images.

However, this constraint doesn't eliminate the value of local development. By testing infrastructure configuration in LocalStack and running your Windows service locally against LocalStack's SQS, you capture most integration issues without cloud deployment costs.

The hybrid approach—LocalStack for AWS infrastructure, local Windows execution for service logic—provides significant development workflow improvements while respecting platform realities. For teams migrating Windows services to containerized architectures, this limitation also encourages consideration of cross-platform runtimes for future development.

LocalStack delivers about 80% of the local development benefits you're seeking. The remaining 20% requires creative solutions, but the overall productivity gains make the effort worthwhile.

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Aaron Rose is a software engineer and technology writer at tech-reader.blog.