Docker Swarm - Route a request to ALL containers

Question

Is there any sort of way to broadcast an incoming request to all containers in a swarm?

EDIT: More info

I have a distributed application with many docker containers. The client can send requests to the swarm and have it respond. However, in some cases, the client needs to change a state on all server instances and therefore I would either need to be able to broadcast a message or have all the Docker containers talk to each other similar to MPI, which I'm trying to avoid.

Answer 1

There is no built-in way to turn a unicast packet into a multicast packet, nor any common 3rd party way of doing (That I've seen or heard of).

I'm not sure what "change a state on all server instances" means. Are we talking about the running state on all containers in a single service? Or the actual underlying OS? All containers on all services? etc.

Without knowing more about your use case, I'd say it's likely better to design something where the request is received by one Swarm service, and then it's stored in a queue system where a backend worker would pick it up and "change the state on all server instances" for you.

Answer 2

It depends on your specific use case. One way to do it is to send a docker service update --force , which will cause all containers to reboot. If your containers fetch the information that is changed at startup, it would have the required effect