[BUG] "docker-compose config" consumes huge amounts of memory with broken config

[ahollmann]

Description

docker-compose config with the following config consumes huge amounts of memory. I had to SIGTERM it with ctrl-c in order not to run out of memory.

The config is obviously broken as services: is missing.

I'm using docker-compose config to verify if the config is correct so it seems to be valid use case.

Version used: Docker Compose version v2.29.7

x-healthcheck: &healthcheck
  healthcheck:
    test: [ "CMD", "wget", "--quiet", "--spider", "--timeout=1", "http://localhost:9000/health/live" ]
    start_period: 20s
    start_interval: 1s
    interval: 30s
    timeout: 2s
    retries: 5


  egress-service:
    <<: *healthcheck

Steps To Reproduce

Create compose.yaml with the input

x-healthcheck: &healthcheck
  healthcheck:
    test: [ "CMD", "wget", "--quiet", "--spider", "--timeout=1", "http://localhost:9000/health/live" ]
    start_period: 20s
    start_interval: 1s
    interval: 30s
    timeout: 2s
    retries: 5


  egress-service:
    <<: *healthcheck

run: docker-compose config

Compose Version

Docker Compose version v2.29.7

Docker Environment

Client: Docker Engine - Community
Version: 27.3.1
Context: default
Debug Mode: false
Plugins:
buildx: Docker Buildx (Docker Inc.)
Version: v0.17.1
Path: /usr/libexec/docker/cli-plugins/docker-buildx
compose: Docker Compose (Docker Inc.)
Version: v2.29.7
Path: /usr/libexec/docker/cli-plugins/docker-compose

Anything else?

No response

[idsulik]

@ahollmann Hi! I think the reason is the recursive alias. the egress-service is located inside the healthcheck alias and the egress-service uses the healthcheck alias

[ahollmann]

@idsulik Thanks. This seems to be the case.

Thanks for creating the MR.

[caseywebdev]

This fix broke references for services that are prefixed with the name of a preceding service.

docker-compose.yaml

services:
  a: &a
    image: alpine
  a2: *a

$ dc config
cycle detected at path: services.a2

Switch the order and see that since the services.a-test prefix hasn't been seen at the point of services.a, it's fine:

docker-compose.yaml

services:
  a2: &a
    image: alpine
  a: *a

$ dc config
...
services:
  a:
    image: alpine
    networks:
      default: null
  a2:
    image: alpine
    networks:
      default: null
...

The fix I believe would be to check the visited path plus a dot, so that at services.a2. in the example would not match the prefix check for services.a.

[idsulik]

@caseywebdev thank you for the details! pushed fix for it compose-spec/compose-go#704