Passive replicas with Docker swarm mode
Active Passive replica can be achieved by having below deployment mode:
mode: global
With this port of the corresponding service is open, i.e., service is accessible via any the nodes in the swarm, but container will be running only on particular node.
Ref: https://docs.docker.com/compose/compose-file/#mode
Example:VAULT-HA with Consul Backend docker stack file:https://raw.githubusercontent.com/gtanand1994/VaultHA/master/docker-compose.yml
Here, Vault and Nginx containers will be seen only in one node in the swarm, but Consul containers (having mode: replicated) will be present on all the nodes of swarm.But as I said before, VAULT, and NGINX services are available via 'any_node_ip:corresponding_port_number'