I’ve just started using docker stack, and ran into a question to which I cannot seem to find an answer.
If I do a ‘docker stack deploy’ on a swarm that has many nodes, what is the behaviour with regard to where the services are spawned?
- • I do a docker stack deploy of a stack that has 5 services
- • Things are set so that only one instance of the stack is deployed
- • But I have a swarm with 5 nodes in it
When the stack deploys, will all 5 services be deployed on the same worker node? Or is it possible for me to have one service deployed on each of the 5 nodes (but all part of the same stack)?
(You may want to answer “why would you care? they are services, and can be anywhere, right?”, but in this case I have volumes shared between the services – this would work only if they are on the same node; or if there were an easy/simple distributed volume plugin for docker (sigh)).
So, in short, does docker stack make any sort of guarantee as to where the services are placed?
Thanks in advance!