There is always a requirement to run every individual service without failover and load balancing. When this comes to container services docker swarm comes into the picture.
Docker swarm is a cluster of docker containers and provide a container orchestration framework like k8s, nomad and apache mesos.
- comprises of managers and workers
- managers are also known as workers
- there will be only one manager as a leader, other managers will act as a backup
- as a pre-requisite, your docker version should be on 1.12+
# to initiate docker swarm$ docker swarm init --advertise-addr ManagerIP:2377 --listen-addr ManagerIP:swarmListenPort
2377 - is the default port for swarm
172.31.22.15 - is my Manger node IP
addvertise-addr - will let swarm manager to use specific IP:PORT.
now creating a SERVICE and running it on docker swarm
(the whole idea of setting this orchestration layer is, we don't need to worry about our app as where it is running but it will be up for the whole time)
addvertise-addr - will let swarm manager to use specific IP:PORT.
[root@Manager1]# docker swarm init --advertise-addr 172.31.22.15:2377 --listen-addr 172.31.22.15:2377Swarm initialized: current node (icuih1r0n8juo8xigkceniu3j) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-15z6ejowo...63dn550as-7998mw9sxnh3ig 172.31.22.15:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
[root@Manager1]# docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
icuih1r0n8juo8xigkceniu3j * docker Ready Active Leader
the highlighted command is the exact command that we need to run on a worker/manager that you wanna join to this swarm, it includes a token
[root@Manager1]# docker swarm join-token manager
To add a manager to this swarm, run the following command:
docker swarm join --token SWMTKN-1-15z6ejowow...63dn550as-9wiyb3pyiviqik 172.31.22.15:2377
[root@Worker1]# docker swarm join-token worker
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-15z6ejowow...63dn550as-7998mw9sxnh3ig 172.31.22.15:2377
following the above command to join leader as worker/manager, launch another ec2 instance or any with docker 1.12+ in it and
you will see all the workers/managers you have joined with your swarm from the Leader node as:
$ docker swarm join --token SWMTKN-1-15z6ejowow53...63dn550as-9wiyb3pyiviqik 172.31.22.15:2377
[root@Manager1]# docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
25nwmw5eg7a5ms4ch93aw0k03 Worker3 Ready Active
icuih1r0n8juo8xigkceniu3j * Manager1 Ready Active Leader
5pm9f2pzr8ndijqkkblkgqbsf Worker2 Ready Active
9yq4lcmfg0382p39euk8lj9p4 Worker1 Ready Active
# docker info will give you a detailed info on your swarm
[root@Manager1]# docker info
Containers: 12
Running: 0
Paused: 0
Stopped: 12
Images: 1
Server Version: 1.13.1
Storage Driver: aufs
Root Dir: /var/lib/docker/aufs
Backing Filesystem: extfs
Dirs: 54
Dirperm1 Supported: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host macvlan null overlay
Swarm: active
NodeID: icuih1r0n8juo8xigkceniu3j
Is Manager: true
ClusterID: hpvfpcevwt8144bj65yk744q8
Managers: 1
Nodes: 6
Orchestration:
.
..
Node Address: 10.91.20.119
Manager Addresses:
10.91.20.119:2377
......
..
(the whole idea of setting this orchestration layer is, we don't need to worry about our app as where it is running but it will be up for the whole time)
$ docker serivce create | update | ls | ps | inspect | rmex:$ docker service update -image=punitporwal07/apache:2.0 --detach=true apache $ docker service scale >> docker service update --replicas $ docker service scale Name=7 $ docker service ps Name$ docker network create -d overlay pp-net$ docker service create --name myswarmapp -p 9090:80 punitporwal07/apache rvzrpe4szt0vdyqte7g7tfshs
accessing the service now:
NOTE: after advertising listen address to the docker swarm, you may get an error next time when you try to initialize the docker daemon. (if you are using dynamic IP)
# below two files hold your IP and failed to initialize docker-daemon/var/lib/docker/swarm/docker-state.json /var/lib/docker/swarm/state.json# sample error message
ERRO[0001] cluster exited with error: failed to listen on remote APIaddress: listen tcp 10.91.20.119:2377: bind: cannot assign requested addressFATA[0001] Error creating cluster component: swarm component couldnot be started: failed to listen on remote API address: listen tcp10.91.20.119:2377: bind: cannot assign requested address
$ service docker restart
k/r,
P