I can't run more than 5 tasks in AWS ECS Fargate

Question

I'm facing a problem when using AWS ECS Fargate on a new AWS account. When I try to run run more than 5 tasks, I get an error saying:

service feedback was unable to place a task. Reason: You've reached the limit on the number of tasks you can run concurrently.

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Answer 1

TL;DR

Run an EC2 instance

More Detail

I raised a support request with AWS after receiving this on a new account. This is their response:

In this situation, in order to activate the requested regions i.e EU (Ireland) and/or other regions, please launch an EC2 instance in those regions, this will enable you to run multiple concurrent Fargate tasks.

Running an t3.medium instance for 10 minutes in eu-west-1 resulted in an email being sent to the account email informing us that:

Your request has now been validated for AWS Europe (Ireland) region(s).

After which, I was able to run more than 2 concurrent ECS Fargate tasks.

Don't forget to terminate your EC2 instance!

Even more detail: Run a basic EC2 instance:

1. https://eu-west-1.console.aws.amazon.com/ec2/v2/home?region=eu-west-1#LaunchInstances:
2. Change to the same region as your ECS cluster
3. Click Launch Instance
4. Name: Test
5. Image: Amazon Linux
6. Architecture: 64-bit x86
7. Instance Type: t3.medium
8. Key pair: Proceed without
9. Network: Uncheck all
10. Storage: 8GB or default
11. Click Launch
12. Wait 10 minutes
13. Goto https://eu-west-1.console.aws.amazon.com/ec2/v2/home?region=eu-west-1#Instances:
14. Select correct region
15. Instant State -> Terminate Instance -> Terminate

Answer 2

All AWS accounts have service limits, to protect you and other accounts.

See the ECS Service Limits page and decide if you need to request an increase in service limits.

In your case, you're using Fargate which has their own service limit separated from ECS service limit. Search for "Fargate" in service limit page and request for the new limit.

Answer 3

Apparently all new account has a limit of 2 tasks that can be run concurrently, which does not seem to be documented anywhere. Increasing the limit fixes the issue.