Docker Swarm#
Feature highlights#
Cluster management integrated with Docker Engine
Decentralized design
Declarative service model
Scaling
Desired state reconciliation
Multi-host networking
Service discovery
Load balancing
Secure by default
Rolling updates
Create a swarm#
docker swarm init
Add nodes to the swarm#
docker swarm join-token worker
docker swarm join-token manager
docker node ls
Deploy a service#
docker service create --replicas 1 --name helloworld alpine ping docker.com
docker service ls
Inspect the service#
docker service inspect --pretty helloworld
docker service inspect helloworld
docker service ps helloworld
docker ps
Scale the service#
docker service scale helloworld=5
docker service ps helloworld
docker ps
Delete the service#
docker service rm helloworld
Apply rolling updates#
docker service create \
--replicas 3 \
--name redis \
--update-delay 10s \
redis:3.0.6
docker service inspect --pretty redis
docker service update --image redis:3.0.7 redis
docker service inspect --pretty redis
docker service update redis
docker service ps redis
Drain a node#
docker service create --replicas 3 --name redis --update-delay 10s redis:3.0.6
docker node update --availability drain worker1
docker node inspect --pretty worker1
docker service ps redis
docker node update --availability active worker1
Use swarm mode routing mesh#
Publish a port for a service#
docker service create \
--name my-web \
--publish published=8080,target=80 \
--replicas 2 \
nginx
docker service inspect --format="{{json .Endpoint.Spec.Ports}}" my-web
Publish a port for TCP only or UDP only#
Long syntax:
docker service create --name dns-cache \
--publish published=53,target=53 \
--publish published=53,target=53,protocol=udp \
dns-cache
Short syntax:
docker service create --name dns-cache \
-p 53:53 \
-p 53:53/udp \
dns-cache
Bypass the routing mesh#
docker service create --name dns-cache \
--publish published=53,target=53,protocol=udp,mode=host \
--mode global \
dns-cache
Configure an external load balancer#
/etc/haproxy/haproxy.cfg
global
log /dev/log local0
log /dev/log local1 notice
...snip...
# Configure HAProxy to listen on port 80
frontend http_front
bind *:80
stats uri /haproxy?stats
default_backend http_back
# Configure HAProxy to route requests to swarm nodes on port 8080
backend http_back
balance roundrobin
server node1 192.168.99.100:8080 check
server node2 192.168.99.101:8080 check
server node3 192.168.99.102:8080 check
How nodes work#
Change roles#
docker node promote
How services work#
Services, tasks, and containers#
Tasks and scheduling#
Replicated and global services#
