CODEWITHSUNDEEP
dockerdocker-composeamazon-ecsdocker-container
overexchange
overexchange

Reputation: 1

DependsOn vs links - docker-compose vs ECS task

DependsOn

property of ECS container definition is used for container dependencies

Links property of docker compose provides service dependencies.

We are mapping a docker compose file to ECS task definition.

Conceptually, Is the purpose of links property in docker compose similar to DependsOn property of ECS container definition?

Upvotes: 0

Views: 1226

Answers (1)

David Maze
David Maze

Reputation: 159040

links: was an important part of the first-generation Docker networking setup. Once Docker introduced the docker network series of commands and Docker Compose set up a private network by default, it became much less important, and there's not really any reason to use it at all in modern Docker.

Compose has its own depends_on: option. If service a depends_on: [b], then when a starts up (maybe because you explicitly docker-compose up a, or maybe just as an ordering constraint) the b container is guaranteed to exist. If b is a database or some other service that takes a while to start up, it's not guaranteed to be functional, but for instance b will be a valid host name from a's point of view.

Within a single ECS task, one container can dependsOn others. This is similar to the Compose depends_on: setting, but it has an additional condition parameter that can support a couple of different lifecycles. Of note, one container can wait for another to be "condition": "HEALTHY", a check that in Docker Compose requires the waiting container to manually check on its own (ofter with a helper script like wait-for-it.sh); it can also wait for another container to "condition": "COMPLETE" if one container just does setup for another.

If you're porting a Docker Compose file to an ECS task, I'd start by trying to replace links: with depends_on:, which shouldn't cause much functional change; translating this to ECS, the semantics of that are very similar to "dependsOn": [{"condition": "START"}].

Upvotes: 1

Related Questions