Service Modes
- Notice it in
docker service ls - Defaults to replicated, but global is an option
- Global = one task per node
- Set on service create only, must remove service to change
- Good for host agents (security, monitoring, backup, proxy, etc.)
- 1.13+ Global Mode can be combined with Constraints
Examples
- Place one task on each node in Swarm
docker service create --mode=global nginx
- Place one task on each Worker in Swarm
docker service create --mode=global --constraint=node.role==worker nginx
Hands On
[node1] ~> docker service create --mode=global --name test1 nginx
q8shwxzsucgwi6b6kijfn55nq
overall progress: 3 out of 3 tasks
rru8z0gj9riq: running [==================================================>]
th2nb6uc5j61: running [==================================================>]
tsojlv10aqlv: running [==================================================>]
verify: Service converged
[node1] ~> docker service create --mode=global --name test2 --constraint=node.role==worker nginx
qlzmyl2fmouim1p5rsxj09l7w
overall progress: 2 out of 2 tasks
tsojlv10aqlv: running [==================================================>]
rru8z0gj9riq: running [==================================================>]
verify: Service converged
It might be good to run special devops or maintenance services on worker nodes (backup, proxy, monitoring, etc.)
Service Modes in Stack Files
version: "3.1"
services:
web:
image: nginx
deploy:
mode: global