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chore(kb/aws/ecs): expand part about capacity providers

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Michele Cereda
2025-07-04 14:35:27 +02:00
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knowledge base/cloud computing/aws/ecs.md
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@@ -2,10 +2,11 @@
1. [TL;DR](#tldr)
1. [How it works](#how-it-works)
1. [Standalone tasks](#standalone-tasks)
1. [Services](#services)
1. [Launch type](#launch-type)
1. [EC2 launch type](#ec2-launch-type)
1. [Fargate launch type](#fargate-launch-type)
1. [Standalone tasks](#standalone-tasks)
1. [Services](#services)
1. [Capacity providers](#capacity-providers)
1. [EC2 capacity providers](#ec2-capacity-providers)
1. [Fargate for ECS](#fargate-for-ecs)
@@ -148,7 +149,7 @@ while [[ $(aws ecs list-tasks --query 'taskArns' --output 'text' --cluster 'test
Tasks must be registered in _task definitions_ **before** they can be launched.
Tasks can be executed as [Standalone tasks] or [services].<br/>
Whatever the _launch type_:
Whatever the [launch type] or [capacity provider][capacity providers]:
1. On launch, a task is created and moved to the `PROVISIONING` state.<br/>
While in this state, ECS needs to find compute capacity for the task and neither the task nor its containers exist.
@@ -164,23 +165,7 @@ Whatever the _launch type_:
1. ECS starts the task's containers.
1. ECS moves the task into the `RUNNING` state.
### EC2 launch type
Starts tasks onto _registered_ EC2 instances.
Instances can be registered:
- Manually.
- Automatically, by using the _cluster auto scaling_ feature to dynamically scale the cluster's compute capacity.
### Fargate launch type
Starts tasks on dedicated, managed EC2 instances that are **not** reachable by the users.
Instances are automatically provisioned, configured, and registered to scale one's cluster capacity.<br/>
The service takes care itself of all the infrastructure management for the tasks.
### Standalone tasks
## Standalone tasks
Refer [Amazon ECS standalone tasks].
@@ -188,7 +173,7 @@ Meant to perform some work, then stop similarly to batch processes.
Can be executed on schedules using the EventBridge Scheduler.
### Services
## Services
Refer [Amazon ECS services].
@@ -238,9 +223,27 @@ Available service scheduler strategies:
Fargate does **not** support the `DAEMON` scheduling strategy.
## Launch type
### EC2 launch type
Starts tasks onto _registered_ EC2 instances.
Instances can be registered:
- Manually.
- Automatically, by using the _cluster auto scaling_ feature to dynamically scale the cluster's compute capacity.
### Fargate launch type
Starts tasks on dedicated, managed EC2 instances that are **not** reachable by the users.
Instances are automatically provisioned, configured, and registered to scale one's cluster capacity.<br/>
The service takes care itself of all the infrastructure management for the tasks.
## Capacity providers
Refer [Capacity providers].
Refer [Capacity providers][upstream capacity providers].
Clusters can contain a mix of tasks that are hosted on Fargate, Amazon EC2 instances, or external instances.<br/>
Tasks can run on Fargate or EC2 infrastructure as a launch type or a capacity provider strategy.<br/>
@@ -249,11 +252,63 @@ Capacity providers manage the scaling of infrastructure for tasks in one's clust
Each cluster can have one or more _capacity providers_, and an optional _capacity provider strategy_.
The capacity provider strategy determines how tasks are spread across a cluster's capacity providers.<br/>
One can assign a **default** capacity provider strategy to a cluster. This strategy **only** applies when one does not
specify a launch type nor a capacity provider strategy for a task or service. If either of these parameters is provided,
the default strategy is ignored.<br/>
One can assign a **default** capacity provider strategy to a cluster.
<details style='padding: 0 0 1rem 1rem'>
```json
{
"clusterName": "some-cluster",
"capacityProviders": [
"FARGATE",
"FARGATE_SPOT"
],
"defaultCapacityProviderStrategy": [
{
"capacityProvider": "FARGATE_SPOT",
"weight": 100,
},
{
"capacityProvider": "FARGATE",
"weight": 0,
}
],
```
</details>
When running a standalone task or creating a service, one can either use the cluster's default capacity provider
strategy or provide one that overrides the default.
strategy or provide one that overrides the default.<br/>
The default capacity provider strategy **only** applies when one does **not** specify a launch type **nor** a capacity
provider strategy for a task or service. If either of these parameters is provided, the cluster's default strategy is
ignored.
<details style='padding: 0 0 1rem 1rem'>
<summary>Override the cluster's default strategy</summary>
```json
{
"serviceName": "some-ecs-service",
… ,
"capacityProviderStrategy": [
{
"capacityProvider": "FARGATE",
"weight": 1,
"base": 1
},
{
"capacityProvider": "FARGATE_SPOT",
"weight": 2
},
{
"capacityProvider": "some-custom-ec2-capacity-provider",
"weight": 0
}
]
}
```
</details>
One must associate a capacity provider with a cluster **before** associating it with a capacity provider strategy.<br/>
Strategies allow to specify a maximum of 20 capacity providers.
@@ -261,7 +316,8 @@ Strategies allow to specify a maximum of 20 capacity providers.
Strategies' weight value defaults to `1` when creating it from the Console, and to `0` if using the API or CLI.
To run tasks on Fargate, one only needs to associate one or more of the pre-defined Fargate-specific capacity providers
with the cluster. This takes away the need to create or manage that cluster's capacity.
with the cluster.<br/>
Leveraging the Fargate providers lifts the need to create or manage that cluster's capacity.
Clusters _can_ contain a mix of Fargate and Auto Scaling group capacity providers. However, a capacity provider strategy
can only contain either Fargate or Auto Scaling group capacity providers, but **not both**.
@@ -269,13 +325,92 @@ can only contain either Fargate or Auto Scaling group capacity providers, but **
One **cannot** update a service that is using an Auto Scaling Group capacity provider to use a Fargate one, and
vice versa.
When multiple capacity providers are specified within a strategy, at least one of the providers **must** have a weight
value greater than zero.<br/>
Capacity providers with a weight of zero are **not** used to run tasks. Should all specified providers in a strategy
have the same weight of zero, any RunTask or CreateService actions using that strategy will fail.
A strategy's capacity provider can have a defined `base` value. This determines the **guaranteed minimum** number of
tasks that that provider will host. If no `base` value is specified for the provider, it defaults to `0`.<br/>
When multiple capacity providers are specified within a strategy, only **one** of them can have a defined `base` value.
In strategies, only **one** capacity provider can have a defined `base` value. If no base value is specified for a
provider, it defaults to zero.
The `weight` value determines **the relative ratio** of tasks to place over the long run, **after the `base` values are
satisfied**.<br/>
When multiple capacity providers are specified within a strategy, at least one of the providers **must** have a `weight`
value greater than zero (`0`).
Capacity providers with a `weight` value of zero are **not** used to run tasks. Should _all_ providers in a strategy
have a weight of `0`, any RunTask or CreateService actions using that strategy will fail.
The `weight` ratio is computed by summing up all providers' weights, then determining the percentage per provider.
<details style='padding: 0 0 0 1rem'>
<summary>Simple example</summary>
Provider 1 is `FARGATE`, with weight of `1`.<br/>
Provider 2 is `FARGATE_SPOT`, with weight of `3`.
```json
{
…
"capacityProviderStrategy": [
{
"capacityProvider": "FARGATE",
"weight": 1,
"base": 1
},
{
"capacityProvider": "FARGATE_SPOT",
"weight": 3
}
],
}
```
Sum of weights: `1 + 3 = 4`.<br/>
Percentage per provider:
- `FARGATE`: `1 / 4 = 0.25`.
- `FARGATE_SPOT`: `3 / 4 = 0.75`.
`FARGATE` will receive 25% of the tasks, while `FARGATE_SPOT` will receive the remaining 75%.
</details>
<details style='padding: 0 0 1rem 1rem'>
<summary>More advanced example</summary>
Provider 1 is `FARGATE`, with a weight of `1` and base of `2`.<br/>
Provider 2 is `FARGATE_SPOT`, with a weight of `19`.<br/>
Provider 3 is `some-custom-ec2-capacity-provider`, with a weight of `0`.
```json
{
…
"capacityProviderStrategy": [
{
"capacityProvider": "FARGATE",
"weight": 1,
"base": 1
},
{
"capacityProvider": "FARGATE_SPOT",
"weight": 19
},
{
"capacityProvider": "some-custom-ec2-capacity-provider",
"weight": 0
}
]
}
```
`some-custom-ec2-capacity-provider` will just be ignored due to its weight being `0`.<br/>
Sum of the remaining weights: `1 + 19 = 20`.<br/>
Percentage per provider:
- `FARGATE`: `1 / 20 = 0.05`.
- `FARGATE_SPOT`: `19 / 20 = 0.95`.
`FARGATE` will receive 2 task for the `base` value being `2`, then 5% of the remaining tasks.<br/>
`FARGATE_SPOT` will receive the remaining 95% of the remaining tasks.
</details>
A cluster can contain a mix of services and standalone tasks that use both capacity providers and launch types.<br/>
Services _can_ be updated to use a capacity provider strategy instead of a launch type, but one will need to force a new
@@ -294,17 +429,20 @@ Refer [AWS Fargate Spot Now Generally Available] and [Amazon ECS clusters for Fa
ECS can run tasks on the `Fargate` and `Fargate Spot` capacity when they are associated with a cluster.
The Fargate provider runs tasks on on-demand compute capacity.
Fargate Spot is intended for **interruption tolerant** tasks.<br/>
runs tasks on spare compute capacity. This makes it cost less the normal Fargate price, but comes with the ability for
AWS to interrupt tasks when it needs capacity back.
It runs tasks on spare compute capacity. This makes it cost less than Fargate's normal price, but allows AWS to
interrupt those tasks when it needs capacity back.
During periods of extremely high demand, Fargate Spot capacity might be unavailable.<br/>
When this happens, ECS services retry launching tasks until the required capacity becomes available.
ECS sends **a two-minute warning** before Spot tasks are stopped due to a Spot interruption. This warning is sent as a
task state change event to EventBridge and as a SIGTERM signal to the running task.
ECS sends **a two-minute warning** before Spot tasks are stopped due to a Spot interruption.<br/>
This warning is sent as a task state change event to EventBridge and as a SIGTERM signal to the running task.
<details style='padding: 0 0 1rem 1rem'>
<summary>EventBridge event example</summary>
```json
{
@@ -332,7 +470,7 @@ task state change event to EventBridge and as a SIGTERM signal to the running ta
</details>
When Spot tasks are terminated, the service scheduler receives the interruption signal and attempts to launch additional
tasks on Fargate Spot if such capacity is available, possibly from a different Availability Zone.
tasks on Fargate Spot, possibly from a different Availability Zone, provided such capacity is available.
Fargate will **not** replace Spot capacity with on-demand capacity.
@@ -341,7 +479,7 @@ Ensure containers exit gracefully before the task stops by configuring the follo
- Specify a `stopTimeout` value of 120 seconds or less in the container definition that the task is using.<br/>
The default value is 30 seconds. A higher value will provide more time between the moment that the task's state change
event is received and the point in time when the container is forcefully stopped.
- Make sure the `SIGTERM` signal is caught from within the container and triggers any cleanup actions.<br/>
- Make sure the `SIGTERM` signal is caught from within the container, and that it triggers any needed cleanup.<br/>
Not processing this signal results in the task receiving a `SIGKILL` signal after the configured `stopTimeout` value,
which may result in data loss or corruption.
@@ -1339,9 +1477,11 @@ Specify a supported value for the task CPU and memory in your task definition.
<!-- In-article sections -->
[bind mounts]: #bind-mounts
[Capacity providers]: #capacity-providers
[docker volumes]: #docker-volumes
[ebs volumes]: #ebs-volumes
[efs volumes]: #efs-volumes
[Launch type]: #launch-type
[resource constraints]: #resource-constraints
[services]: #services
[standalone tasks]: #standalone-tasks
@@ -1368,7 +1508,6 @@ Specify a supported value for the task CPU and memory in your task definition.
[Automatically scale your Amazon ECS service]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/service-auto-scaling.html
[AWS Distro for OpenTelemetry]: https://aws-otel.github.io/
[AWS Fargate Spot Now Generally Available]: https://aws.amazon.com/blogs/aws/aws-fargate-spot-now-generally-available/
[Capacity providers]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/clusters.html#capacity-providers
[Centralized Container Logging with Fluent Bit]: https://aws.amazon.com/blogs/opensource/centralized-container-logging-fluent-bit/
[ecs execute-command proposal]: https://github.com/aws/containers-roadmap/issues/1050
[Example Amazon ECS task definition: Route logs to FireLens]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/firelens-taskdef.html
@@ -1386,6 +1525,7 @@ Specify a supported value for the task CPU and memory in your task definition.
[troubleshoot amazon ecs deployment issues]: https://docs.aws.amazon.com/codedeploy/latest/userguide/troubleshooting-ecs.html
[troubleshoot amazon ecs task definition invalid cpu or memory errors]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-cpu-memory-error.html
[Under the hood: FireLens for Amazon ECS Tasks]: https://aws.amazon.com/blogs/containers/under-the-hood-firelens-for-amazon-ecs-tasks/
[upstream capacity providers]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/clusters.html#capacity-providers
[use amazon ebs volumes with amazon ecs]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ebs-volumes.html
[use amazon efs volumes with amazon ecs]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/efs-volumes.html
[use bind mounts with amazon ecs]: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/bind-mounts.html