ECS EC2 launch type and event was unable to place a task because no container instance met all of its requirements

Question

I'm trying to learn more about ECS with `EC2 launch type`.

Sometimes, when updating the `Task Definition` or `Service` I see the following error in the Service `events`

```
service ecs-service was unable to place a task because no container instance met all of its requirements. The closest matching container-instance XXX has insufficient CPU units available. For more information, see the Troubleshooting section.
```

I checked the suggested docs: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/troubleshooting.html

I also checked: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/service-event-messages.html

In my `Task Definition` I have:
* For the `Task Definition` CPU `2048` and Memory `1024`
* For the `container` CPU `1024` and Memory `1024` (I tried also setting the CPU value to `2048`).

**Why this happens randomly?
What can I do to fix it? When this happens the service seems to get stuck and even after long waits, nothing happens.**

Answer

Hi,
here there is a nice summary of all the reason behind the issue that you are facing https://repost.aws/knowledge-center/ecs-container-instance-requirement-error

* Not enough memory for your tasks
* Not enough CPU units for your container instance 
* No container instances were found in your cluster
* The port needed by the task is already in use
* Not enough available elastic network interface attachment points
* A required attribute is missing for your container instance

The first 2 of the list are the one that most likely happening if you select a small EC2 instance to perform your tests

ECS EC2 launch type and event was unable to place a task because no container instance met all of its requirements

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