Docker : Swarm Cluster2021/04/06 |
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Configure Docker Swarm to create Docker Cluster with multiple Docker nodes.
On this example, Configure Swarm Cluster with 3 Docker nodes like follows.
There are 2 roles on Swarm Cluster, those are [Manager nodes] and [Worker nodes]. This example shows to set those roles like follows.
-----------+---------------------------+--------------------------+------------
| | |
eth0|10.0.0.51 eth0|10.0.0.52 eth0|10.0.0.53
+----------+-----------+ +-----------+----------+ +-----------+----------+
| [ node01.srv.world ] | | [ node02.srv.world ] | | [ node03.srv.world ] |
| Manager | | Worker | | Worker |
+----------------------+ +----------------------+ +----------------------+
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| [1] | |
| [2] | Change settings for Swarm mode on all nodes. |
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root@node01:~#
vi /etc/docker/daemon.json # create new # disable live-restore feature (impossible to use it on Swarm mode)
{
"live-restore": false
}
[root@node01 ~]#
systemctl restart docker
# if Firewalld is running, allow ports [root@node01 ~]# firewall-cmd --add-port={2377/tcp,7946/tcp,7946/udp,4789/udp} --permanent success [root@node01 ~]# firewall-cmd --reload success |
| [3] | Configure Swarm Cluster on Manager Node. |
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root@node01:~# docker swarm init
Swarm initialized: current node (bs01c7zj7r1bo8t7qx7nt4p34) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-1crqgsg3qoy8ocft9mpav8lgo3zsjf1th2s3n7wb9t9yry6tif-9ks9ex89nxnl89bg7jrzcwi6j 10.0.0.51:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
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| [4] | Join in Swarm Cluster on all Worker Nodes. It's OK to run the command which was shown when running swarm init on Manager Node. |
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root@node02:~# docker swarm join \ --token SWMTKN-1-1crqgsg3qoy8ocft9mpav8lgo3zsjf1th2s3n7wb9t9yry6tif-9ks9ex89nxnl89bg7jrzcwi6j 10.0.0.51:2377 This node joined a swarm as a worker. |
| [5] | Verify with a command [node ls] that worker nodes could join in Cluster normally. |
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root@node01:~# docker node ls ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION bs01c7zj7r1bo8t7qx7nt4p34 * node01.srv.world Ready Active Leader 20.10.5 pu0szo4f3fr9nn5zn87n77cyp node02.srv.world Ready Active 20.10.5 x0q143322alhmukkj94b9we7b node03.srv.world Ready Active 20.10.5 |
| [6] | Verify Cluster works normally to create a test service. For example, create a web service containers and configure Swarm service. Generally, it is used a container image on a rgistry on all Nodes, but on this example, create container images on each Node to verify settings and accesses for Swarm Cluster. |
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root@node01:~#
vi Dockerfile FROM centos MAINTAINER ServerWorld <admin@srv.world> RUN dnf -y install nginx RUN echo "Nginx on node01" > /usr/share/nginx/html/index.html EXPOSE 80 CMD ["/usr/sbin/nginx", "-g", "daemon off;"] docker build -t nginx-server:latest . |
| [7] | Configure service on Manager Node. After successing to configure service, access to the Manager node's Hostname or IP address to verify it works normally. Access requests to worker nodes are load-balanced with round-robin like follows. |
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root@node01:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE nginx-server latest 5185329f1a74 About a minute ago 289MB centos latest 300e315adb2f 3 months ago 209MB # create a service with 2 repricas root@node01:~# docker service create --name swarm_cluster --replicas=2 -p 80:80 nginx-server:latest 64pa21potpdbq1hmxbzuu3tam overall progress: 0 out of 2 tasks 1/2: preparing 2/2: preparing ..... ..... # show service list root@node01:~# docker service ls ID NAME MODE REPLICAS IMAGE PORTS 64pa21potpdb swarm_cluster replicated 2/2 nginx-server:latest *:80->80/tcp # inspect the service root@node01:~# docker service inspect swarm_cluster --pretty ID: 64pa21potpdbq1hmxbzuu3tam Name: swarm_cluster Service Mode: Replicated Replicas: 2 Placement: UpdateConfig: Parallelism: 1 On failure: pause Monitoring Period: 5s Max failure ratio: 0 Update order: stop-first RollbackConfig: Parallelism: 1 On failure: pause Monitoring Period: 5s Max failure ratio: 0 Rollback order: stop-first ContainerSpec: Image: nginx-server:latest Init: false Resources: Endpoint Mode: vip Ports: PublishedPort = 80 Protocol = tcp TargetPort = 80 PublishMode = ingress # show service state root@node01:~# docker service ps swarm_cluster ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS pbjvpqru195w swarm_cluster.1 nginx-server:latest node02.srv.world Running Running 47 seconds ago uwndpoduvpoy swarm_cluster.2 nginx-server:latest node01.srv.world Running Running 47 seconds ago # verify it works normally root@node01:~# curl node01.srv.world Nginx on node02 root@node01:~# curl node01.srv.world Nginx on node01 root@node01:~# curl node01.srv.world Nginx on node02 root@node01:~# curl node01.srv.world Nginx on node01 |
| [8] | If you'd like to change the number of repricas, configure like follows. |
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# change repricas to 3 root@node01:~# docker service scale swarm_cluster=3 swarm_cluster scaled to 3 overall progress: 2 out of 3 tasks 1/3: running 2/3: running 3/3: preparing ..... .....root@node01:~# docker service ps swarm_cluster ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS pbjvpqru195w swarm_cluster.1 nginx-server:latest node02.srv.world Running Running about a minute ago uwndpoduvpoy swarm_cluster.2 nginx-server:latest node01.srv.world Running Running about a minute ago r7lmkav7hxpt swarm_cluster.3 nginx-server:latest node03.srv.world Running Running 15 seconds ago # verify accesses root@node01:~# curl node01.srv.world Nginx on node01 root@node01:~# curl node01.srv.world Nginx on node03 root@node01:~# curl node01.srv.world Nginx on node02 |
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