Docker-compose: Start container after another with timeout - docker

Question

Is it possible to start myapp-1 with myapp-2, then sleep for 30 seconds and only then start myapp-3?
Tried this docker-compose.yml with no luck.
version: '3'
services:
myapp-1:
container_name: myapp-1
image: myapp:latest
restart: always
myapp-2:
container_name: myapp-2
image: myapp:latest
restart: always
test-sleep:
image: busybox
command: ["/bin/sleep", "30"]
depends_on:
- "myapp-1"
- "myapp-2"
myapp-3:
container_name: myapp-3
image: myapp:latest
restart: always
depends_on:
- "test-sleep"

Answer 1

The docker-compose.yml you proposed could not address your use case, as the depends_on property does not wait for the dependencies to be ready (or terminated), but only for them to be started (i.e., in your example, myapp-3 is started as soon as the /bin/sleep 30 command has been started).
See e.g. the corresponding doc:
depends_on does not wait for [dependencies] to be “ready” before starting [the service] - only until they have been started. If you need to wait for a service to be ready, see Controlling startup order for more on this problem and strategies for solving it.
The link above mentions several tools (including wait-for-it) that could be used to wait that some service dependencies are ready (provided they expose a web service at a given TCP port).
Otherwise, if you just want to wait for 30s before starting myapp-3, assuming the Dockerfile of myapp-3 contains CMD ["/prog", "first argument"], you could just get rid of test-sleep and write something like:
version: '3'
services:
myapp-1:
container_name: myapp-1
image: myapp:latest
restart: always
myapp-2:
container_name: myapp-2
image: myapp:latest
restart: always
myapp-3:
container_name: myapp-3
image: myapp:latest
restart: always
command:
- '/bin/sh'
- '-c'
- '/bin/sleep 30 && /prog "first argument"'
depends_on:
- "myapp-1"
- "myapp-2"