Add depends_on in docker compose

[nook0110]

I think some wrong solutions (for example my first one) can rely on the 'server' starting before 'clients'. I propose a crutch for this. It can catch some "naive" solutions

[lodthe]

You should never expect server is started before clients. Even depends_on doesn't guarantee that. It guarantees the container start order, but you have to add extra steps to verify that server is ready to accept and process requests, and only after that start client containers. Not sure if it's possible to combine depends_on and readiness probes in docker.

The correct way to handle that is to add retries on the client side / or set up "restart always" policy for clients. Clients should gracefully handle temporary server's unavailability.

[nook0110]

You should never expect server is started before clients. Even depends_on doesn't guarantee that. It guarantees the container start order, but you have to add extra steps to verify that server is ready to accept and process requests, and only after that start client containers. Not sure if it's possible to combine depends_on and readiness probes in docker.

The correct way to handle that is to add retries on the client side / or set up "restart always" policy for clients. Clients should gracefully handle temporary server's unavailability.

@lodthe

That's the reason of this pr... it makes the server container start AFTER clients, so it will catch some wrong solutions