Shepherd
A Docker swarm service for automatically updating your services whenever their base image is refreshed.
Usage
docker service create --name shepherd \
--replicas 1 \
--constraint "node.role==manager" \
--env SLEEP_TIME='5m' \
--env SERVICE_LIST='services.lst'
--mount type=bind,source=/path_to_service_list,target=/tmp,ro \
--mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock,ro \
mazzolino/shepherd
Shepherd will try to update your services every 5 minutes but you can change this value by changing the value of the SLEEP_TIME variable.
You need to create a file called services.lst which contain the list of services you have and which ones can be updated using shepherd and which one can't . you can change the name by changing the value of the SERVICE_LIST variable
To update a service called shepherd, you will add w:shepherd in services.lst To prevent update of a service called registry you will add b:registry in services.lst A service not declared it services.lst will be considered as blacklisted (b:) and won't be upgraded
How does it work?
Shepherd just triggers updates by updating the image specification for each service, removing the current digest.
Most of the work is thankfully done by Docker which resolves the image tag, checks the registry for a newer version and updates running container tasks as needed.
Also, Docker handles all the work of applying rolling updates. So at least with replicated services, there should be no noticeable downtime.