How do I connect to an ECS service running on Fargate?

Question

I'm building a slack app, and my application is expected to receive webhook calls from slack. SO I need to give Slack the "endpoint URL for my service"

I'm not sure I understand what AWS bricks I need to put together to make this work. So far, I have configured my service using Fargate and it is running on ECS with 1 task.

I'm not really sure how I can successfully connect the internet (slack) to my container instance. How do I make an "endpoint" that slack can send requests to ? I believe I need to use API Gateway for this, but I'm not sure how I'm supposed to configure API Gateway so it redirect my URLs to my ECS service...?

Notes :

I am not planning to have more than one task right now, so it would be more convenient if I did not have to setup a load balancer
However I'm planning to make some regular updates to the service itself, and the tasks will be restarted often

Don't know much about Fargate, but your endpoint need to be able to receive HTTP requests. So you basically need a web server running at the endpoint. — Erik Kalkoken
That's a given and already what I had. The problem is how do I route traffic to my container instance / how do I configure a DNS entry to route to my container — Cyril Duchon-Doris
In general you need to create an "A record" with the server name that points to the IP address of your web server, e.g.` mydomain.example.com` — Erik Kalkoken

Cyril Duchon-Doris Cyril Duchon-Doris · Accepted Answer · 2019-10-10T17:25:09

I'm not sure if there's an alternative or not, but when setting up a service on fargate, in order to receive traffic you will need

To have a load balancer (either an ALB or NLB should work)
In case of an ALB, a target group targeting "IP" must be created
It's only during the creation of the service that you can select to put your containers behind a target group or ALB

For instance, to distribute traffic from a target group, you can use this to configure the service

"loadBalancers": [
        {
            "containerName": "your-container-name-app",
            "containerPort": 80,
            "targetGroupArn": "arn:aws:elasticloadbalancing:eu-central-1:account-id:targetgroup/targetgroup-name/RANDOM-ID"
        }
    ],

Create the target group like this

aws elbv2 create-target-group \
--name targetgroup-name \
--protocol HTTP \
--port 80 \
--vpc-id vpc-YOUR_VPC_ID \
--health-check-protocol HTTP \
--health-check-path /healthcheck \
--target-type ip

So you'll basically use the load balancer DNS to route traffic to your instances. Using an ALB, you can easily intercept a certain path (eg /slack/*) to route to your specific target group, so the same ALB can be used for multiple different services.

But you need a load balancer, and cannot target Fargate containers directly from what I understand.

How do I connect to an ECS service running on Fargate?

1 Answers