Amazon's EC2 Container Service allows you to run any amount of containers you want, it will choose an EC2 instance(s) to run the containers on automatically. Which are great features. However, we are really concerned about automatic scalability.
Scenario:
- I launch a container via AWS ECS Console.
- The HTTP requests are starting to come up.
- The HTTP load increases significantly with time.
- CPU (or RAM) usage of the container is getting closer to 100%.
Question 1: Will ECS run one more container automatically?
Question 2: Will ECS automatically shut one of the containers down when CPU (or RAM) load gets low?
No, you don't get fully automated scaling with basic ECS. What you can do is create an alarm for when load gets high and have the alarm trigger an update to increase the cluster size.
Update Nov 29, 2017
AWS Fargate is a technology for Amazon ECS and EKS* that allows you to
run containers without having to manage servers or clusters. With AWS
Fargate, you no longer have to provision, configure, and scale
clusters of virtual machines to run containers.
This allows to scale containers without worrying about underneath infrastructure working with ECS service level scaling configurations.
You should ideally put scaling both at the ec2 and ecscontainer level.
In case you are using ASGs, ec2 scaling based on the cloudwatch alarms can be configured on the ASG.
For container scaling you will have to write a lambda function or have some sort of application which can be triggered on an cloudwatch alarm for the scaling to occur.
On May 18th 2016, ECS has released autoscaling capability. you wont need Lambda to build scaling capability at service level.
Please see the release and feature documentation below
https://aws.amazon.com/about-aws/whats-new/2016/05/amazon-ec2-container-service-supports-automatic-service-scaling/
http://docs.aws.amazon.com/AmazonECS/latest/developerguide/service-auto-scaling.html
So it doesn't say so explicitly and Nathaniel could certainly be correct but this blog from April 9th this year seems to imply at least that you can do what you are asking
Long-Running Applications Previously, Amazon ECS included two ways to
schedule Docker containers on a cluster. You could run tasks once for
processes such as batch jobs that perform work and then stop. You
could also make calls to the Amazon ECS APIs to retrieve state
information about the cluster and then use it to power a third-party
or custom-written scheduler.
With today’s launch you can also use the new Amazon ECS Service
scheduler to manage long-running applications and services. The
Service scheduler helps you maintain application availability and
allows you to scale your containers up or down to meet your
application’s capacity requirements. Here’s what it does for you:
Load Balancing – The Service scheduler allows you to distribute
traffic across your containers using Elastic Load Balancing. Amazon
ECS will automatically register and deregister your containers from
the associated load balancer. Health Management – The Service
scheduler will also automatically recover containers that become
unhealthy (fail ELB health checks) or stop running to make sure that
you have the desired number of healthy containers available to run
your application. Scale-Up and Scale-Down – You can scale your
application up and down by changing the number of containers you want
the service to run. Update Management – You can update your
application by changing its definition or using a new image. The
scheduler will automatically start new containers using the new
definition and stop containers running the previous version. It will
wait for the ELB connections to drain if ELB is used. You can also use
these new facilities to implement a basic service discovery model. You
can list the services that are running in a cluster and then use the
ELB as the service endpoint.
As of Dec 2017 Amazon announced the new service called Fargate. Quoting the link:
AWS Fargate makes it easy to scale your applications. You no longer have to worry about provisioning enough compute resources for your container applications. After you define your application requirements (e.g., CPU, memory, etc.), AWS Fargate manages all the scaling and infrastructure needed to run your containers in a highly-available manner. You no longer have to decide when to scale your clusters or pack them for optimal utilization.
I assume the bold text means that Fargate will scale up and down the resources for me. Not 100% sure though.
