Docker Swarm

Docker is a free package management tool which helps us in package management, Docker is a platform designed to help us build, share, and run container applications.

Docker Swarm is a feature of Docker that allows you to set up a cluster consisting of one manager and multiple worker nodes. These nodes work together in a tightly coupled manner to meet the service requirements.

Docker swarm gives us different features as

--> Deployment

--> Scaling

--> Resource allocation

--> Load balancing

--> Health Monitoring

Now we will see how docker swarm works and how to use it.

1. Create one node/system as master/manager

   docker swarm init

For understanding purposes, I am creating 4 instances on AWS as swarm workers.

Swarm manager:- 172-31-34-90 is the IP address of the manager node

ubuntu@ip-172-31-34-90:~$ docker swarm init
Swarm initialized: current node (va2uul58txk146aboh0wrdlz9) is now a manager.

To add a worker to this swarm, run the following command:

    docker swarm join --token SWMTKN-1-2v6eh96i1pui7kiypxvjitvf0sr18331ln6srx95i72in8whgs-7e988wvdua2lwwqm9lmf3rn3k 172.31.34.90:2377

To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.

Swarm worker 1:- -172-31-33-90

ubuntu@ip-172-31-33-90:~$ docker swarm join --token SWMTKN-1-2v6eh96i1pui7kiypxvjitvf0sr18331ln6srx95i72in8whgs-7e988wvdua2lwwqm9lmf3rn3k 172.31.34.90:2377
This node joined a swarm as a worker.
ubuntu@ip-172-31-33-90:~$

Swarm worker2:- 172-31-45-118

ubuntu@ip-172-31-45-118:~$ docker swarm join --token SWMTKN-1-2v6eh96i1pui7kiypxvjitvf0sr18331ln6srx95i72in8whgs-7e988wvdua2lwwqm9lmf3rn3k 172.31.34.90:2377
This node joined a swarm as a worker.
ubuntu@ip-172-31-45-118:~$

Swarm woker3:- 172-31-34-64

ubuntu@ip-172-31-34-64:~$ docker swarm join --token SWMTKN-1-2v6eh96i1pui7kiypxvjitvf0sr18331ln6srx95i72in8whgs-7e988wvdua2lwwqm9lmf3rn3k 172.31.34.90:2377
This node joined a swarm as a worker.
ubuntu@ip-172-31-34-64:~$

2. Docker Node details

   docker node ls

    ID                            HOSTNAME           STATUS    AVAILABILITY   MANAGER STATUS   ENGINE VERSION
    jlr9d7g7b01a6b6nmzqj0horj     ip-172-31-33-90    Ready     Active                          24.0.7
    yknnlgi3eha40rl9re9ufwfy2     ip-172-31-34-64    Ready     Active                          24.0.7
    va2uul58txk146aboh0wrdlz9 *   ip-172-31-34-90    Ready     Active         Leader           24.0.7
    c9ogu8mj702nsf1g47ev98ut1     ip-172-31-45-118   Ready     Active                          24.0.7
   

3. Create docker service

   docker service create --name mysql-ser --replicas 6 -e MYSQL_ROOT_PASSWORD=abc@123 --publish 3306:3306 mysql:5.7

    ubuntu@ip-172-31-34-90:~$ docker service create --name mysql-ser --replicas 6 -e MYSQL_ROOT_PASSWORD=abc@123 --publish 3306:3306 mysql:5.7
    rf9k878fziq8wbttxco591igg
    overall progress: 6 out of 6 tasks 
    1/6: running   [==================================================>] 
    2/6: running   [==================================================>] 
    3/6: running   [==================================================>] 
    4/6: running   [==================================================>] 
    5/6: running   [==================================================>] 
    6/6: running   [==================================================>] 
    verify: Service converged
   

   We created 6 replicas of the MySQL service, and they were distributed across 4 nodes.

    ubuntu@ip-172-31-34-90:~$ docker ps
    CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                 NAMES
    3075ba5f92c8   mysql:5.7   "docker-entrypoint.s…"   7 minutes ago   Up 7 minutes   3306/tcp, 33060/tcp   mysql-ser.2.t6eimv95e31hxux065fmn2tae
    ubuntu@ip-172-31-34-90:~$ 
    SWARM MANAGER
   

    ubuntu@ip-172-31-33-90:~$ docker ps
    CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                 NAMES
    a5c37fc07a71   mysql:5.7   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   3306/tcp, 33060/tcp   mysql-ser.3.wj6jdtcgnjps4aexu0uksjft3
    ubuntu@ip-172-31-33-90:~$ 
    WORKER 1
   

    ubuntu@ip-172-31-45-118:~$ docker ps
    CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                 NAMES
    318b6860df5c   mysql:5.7   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   3306/tcp, 33060/tcp   mysql-ser.6.uw4cb6cavbpaj8nerf4gv8adc
    39a025f1f807   mysql:5.7   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   3306/tcp, 33060/tcp   mysql-ser.4.sx1rkoxz86mdco8kudwkilz5b
    WORKER 2
   

    ubuntu@ip-172-31-34-64:~$ docker ps
    CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                 NAMES
    1b55fe40bcd2   mysql:5.7   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   3306/tcp, 33060/tcp   mysql-ser.1.jybhw825yy20li11ruvdd77th
    ec9585249600   mysql:5.7   "docker-entrypoint.s…"   3 minutes ago   Up 3 minutes   3306/tcp, 33060/tcp   mysql-ser.5.wwnwxwjixwys94m2kjl8vuxyf
    WORKER 3
   

   Currently, there are 6 replicas of the MySQL server working, we can check by

    ubuntu@ip-172-31-34-90:~$ docker service ls
    ID             NAME        MODE         REPLICAS   IMAGE       PORTS
    rf9k878fziq8   mysql-ser   replicated   6/6        mysql:5.7   *:3306->3306/tcp
   

4. Scale down the service

   docker service scale mysql-ser=5

    docker service scale mysql-ser=5
    mysql-ser scaled to 5
    overall progress: 5 out of 5 tasks 
    1/5: running   [==================================================>] 
    2/5: running   [==================================================>] 
    3/5: running   [==================================================>] 
    4/5: running   [==================================================>] 
    5/5: running   [==================================================>] 
    verify: Service converged
   

Today, I learned about Docker Swarm and practised by setting up a Docker cluster with one node as the manager and the others as workers.

Thank You.....