It is not possible to retrieve the hostname of a swarm replica using cc-runtime 3.0.4 with docker 17.06-ce as it leaves the replicas in "create" state.

$docker swarm init
Swarm initialized: current node (cl0wp2btl2e2gt0yaeh33m2og) is now a manager.

$ docker service create --name testswarm --replicas 1 --publish 8080:80 mcastelino/nginx /bin/bash -c "hostname > /usr/share/nginx/html/hostname; nginx -g "daemon off;"" 2> /dev/null
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$docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b017d21f121c mcastelino/nginx:latest "/bin/bash -c 'hostna" 2 minutes ago Created testswarm.1.3jjt16h597dko31tjgb8pfegy

Setup:
cc-runtime : 3.0.4
commit : 28bd75d
OCI specs: 1.0.0-rc5