Docker services are not automatically rebalanced after events that affect Docker Swarm nodes, so you have to initiate this process yourself.
Display tasks for specific service.
Both tasks are running on the same server due to unexpected swarm-margay server restart.
$ docker service ps blog_production
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS z6uimamz8dkw blog_production.1 registry.example.org/websites/blog:production swarm-coloclo Running Running 2 minutes ago 7bpspre223bc \_ blog_production.1 registry.example.org/websites/blog:production swarm-margay Shutdown Shutdown 5 minutes ago 4vttp5y5pk30 blog_production.2 registry.example.org/websites/blog:production swarm-coloclo Running Running 2 minutes ago 52rh7rj8izqe \_ blog_production.2 registry.example.org/websites/blog:production swarm-margay Shutdown Shutdown 2 minutes ago
Initiate service rebalance by forcing an update.
You need to force this update as there are no changes to be applied, so no action would be taken by default.
$ docker service update --force blog_production
blog_production overall progress: 2 out of 2 tasks 1/2: running [==================================================>] 2/2: running [==================================================>] verify: Service converged
Display tasks to verify that service is rebalanced.
$ docker service ps blog_production
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS 0e3i9bj9tz3c blog_production.1 registry.example.org/websites/blog:production swarm-coloclo Running Running about a minute ago c2vzwb753bc7 blog_production.2 registry.example.org/websites/blog:production swarm-margay Running Running 2 minutes ago
Additional notes
Please read Re-balance swarm tasks when new nodes join #24103 GitHub issue for some interesting insights.