Deploying Cassandra on ECS?

Question

I'm trying to deploy Cassandra on AWS ECS as docker containers. Single nodes are easily done, but now I'm trying to make a cluster for it.

Cassandra needs fixed ip addresses, at least for the seed nodes, which needs to be passed to all nodes in a cluster. Cassandra cannot work with ELB addresses, because the ELB name resolves to a different ip as the docker host itself.

So basically I need to be able to force AWS to deploy an image to a specific instance/host/ip. In that way I can pass the correct configuration while running the docker image.

Could I use the RunTask api and pass it PlacementConstraint giving a constraint to limit the hosts to a single one, based on IP? Is PrivateIp an attribute of an EC2 instance in this interface?

Do you have any other good ideas how I can achieve that?

Thanks!

Answer 1

You can use hostnames in the seeds list. Just make sure that your seeds will use those names. Also, if a seed stops and resolves to another IP you'll need to replace it (but that's true for any node that changes its IP)

Answer 2

If seed ecs containers are added using awsvpc network mode then each task get their own eni. After you launch seed nodes you can use 'aws describe-tasks' API to get their ip address and update your Cassandra.yml accordingly