Docker Swarm Init
$ docker swarm init --advertise-addr 192.168.99.100
Swarm initialized: current node (3ukhpra7zfoz6a1phx3mayth1) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-0hn48r8yx3lxr0vwz7t8b39akqm1gukjeie67c4ipomfq54qd9-29sv3h2u5ip07rnor5bjmh39y 192.168.99.100:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
--advertise-addr flag configures the manager node to publish its address as 192.168.99.100. The other nodes in the swarm must be able to access the manager at the IP address.The output includes the commands to join new nodes to the swarm. Nodes will join as managers or workers depending on the value for the
--token flag.docker swarm init with no arguments. There is no need to specify--advertise-addr in this case. To learn more, see the topic on how to Use Docker Desktop or Mac or Docker Desktop for Windows with Swarm.Run docker info to view the current state of the swarm:
$ docker info
Client:
Debug Mode: false
Plugins:
app: Docker App (Docker Inc., v0.9.1-beta3)
Server:
Containers: 4
Running: 2
Paused: 0
Stopped: 2
Images: 13
Server Version: 19.03.11
Storage Driver: overlay2
Backing Filesystem: xfs
Supports d_type: true
Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: active
NodeID: 3ukhpra7zfoz6a1phx3mayth1
Is Manager: true
ClusterID: lknzb8g9tgmgp6cumnw2qqo7i
Managers: 1
Nodes: 1
Default Address Pool: 10.0.0.0/8
SubnetSize: 24
Data Path Port: 4789
Orchestration:
Task History Retention Limit: 5
Raft:
Snapshot Interval: 10000
Number of Old Snapshots to Retain: 0
Heartbeat Tick: 1
Election Tick: 10
Dispatcher:
Heartbeat Period: 5 seconds
CA Configuration:
Expiry Duration: 3 months
Force Rotate: 0
Autolock Managers: false
Root Rotation In Progress: false
Node Address: 127.0.0.1
Manager Addresses:
127.0.0.1:2377
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 7ad184331fa3e55e52b890ea95e65ba581ae3429
runc version: dc9208a3303feef5b3839f4323d9beb36df0a9dd
init version: fec3683
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 4.4.0-96-generic
Operating System: Alpine Linux v3.12 (containerized)
OSType: linux
Architecture: x86_64
CPUs: 8
Total Memory: 31.4GiB
Name: node1
ID: N37T:M2Y6:XFOS:FNZI:HVOV:KXHH:ZC5W:OK3U:5A4H:VKDZ:M63T:SWYR
Docker Root Dir: /var/lib/docker
Debug Mode: true
File Descriptors: 54
Goroutines: 167
System Time: 2020-09-07T08:11:13.359727764Z
EventsListeners: 0
Registry: https://index.docker.io/v1/
Labels:
Experimental: true
Insecure Registries:
127.0.0.1
127.0.0.0/8
Live Restore Enabled: false
Product License: Community Engine
WARNING: API is accessible on http://0.0.0.0:2375 without encryption.
Access to the remote API is equivalent to root access on the host. Refer
to the 'Docker daemon attack surface' section in the documentation for
more information: https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface
WARNING: No swap limit support
WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled
Run the docker node ls command to view information about nodes:
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
dxn1zf6l61qsb1josjja83ngz * manager1 Ready Active Leader
The * next to the node ID indicates that you’re currently connected on this node.
Docker Engine swarm mode automatically names the node for the machine host name. The tutorial covers other columns in later steps.
Add nodes to the swarm
Once you’ve created a swarm with a manager node, you’re ready to add worker nodes.
Open a terminal and ssh into the machine where you want to run a worker node. This tutorial uses the name worker1.
Run the command produced by the docker swarm init output from the Create a swarm tutorial step to create a worker node joined to the existing swarm:
$ docker swarm join \
--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
192.168.0.28:2377
This node joined a swarm as a worker. # This node's ip is 192.168.0.27
- Open a terminal and ssh into the machine where the manager node runs and
- run the
docker node lscommand to see the worker nodes:
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
3ukhpra7zfoz6a1phx3mayth1 * node1 Ready Active Leader 19.03.11
ujaw7yd9n932w72i48d01grsk node2 Ready Active 19.03.11
15dss2zuext1jw28418nugg9x node3 Ready Active 19.03.11The MANAGER column identifies the manager nodes in the swarm. The empty status in this column for worker1 and worker2 identifies them as worker nodes.
Swarm management commands like docker node ls only work on manager nodes.
Deploy a service to the swarm
After you create a swarm, you can deploy a service to the swarm. For this tutorial, you also added worker nodes, but that is not a requirement to deploy a service.
Open a terminal and ssh into the machine where you run your manager node. For example, the tutorial uses a machine named manager1.
Run the following command:
$ docker service create --replicas 1 --name helloworld alpine ping docker.com
9uk4639qpg7npwf3fn2aasksr
- The
docker service create command creates the service. - The
--name flag names the service helloworld. - The
--replicas flag specifies the desired state of 1 running instance. - The arguments
alpine ping docker.com define the service as an Alpine Linux container that executes the command ping docker.com.
Run docker service ls to see the list of running services:
$ docker service ls
ID NAME SCALE IMAGE COMMAND
9uk4639qpg7n helloworld 1/1 alpine ping docker.com
Inspect a service on the swarm
When you have deployed a service to your swarm, you can use the Docker CLI to see details about the service running in the swarm.
If you haven’t already, open a terminal and ssh into the machine where you run your manager node. For example, the tutorial uses a machine named manager1.
Run docker service inspect --pretty <SERVICE-ID> to display the details about a service in an easily readable format.
To see the details on the helloworld service:
[manager1]$ docker service inspect --pretty helloworld
ID: gg8j8u8qhwtvfbz4kphkx4e1c
Name: helloworld
Service Mode: Replicated
Replicas: 1
Placement:
UpdateConfig:
Parallelism: 1
On failure: pause #can change to restart
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: alpine:latest@sha256:185518070891758909c9f839cf4ca393ee977ac378609f700f60a771a2dfe321
Args: ping docker.com
Init: false
Resources:
Endpoint Mode: vip
Tip: To return the service details in json format, run the same command without the --pretty flag.
Run docker service ps <SERVICE-ID> to see which nodes are running the service:
[manager1]$ docker service ps helloworld
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
roelhski88xz helloworld.1 alpine:latest node1 Running Running 5 minutes ago
Swarm also shows you the DESIRED STATE and CURRENT STATE of the service task so you can see if tasks are running according to the service definition.
Run docker ps on the node where the task is running to see details about the container for the task.
Tip: If helloworld is running on a node other than your manager node, you must ssh to that node.
[worker2]$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
70038e250789 alpine:latest "ping docker.com" 7 minutes ago Up 7 minutes
Scale the service in the swarm
Once you have deployed a service to a swarm, you are ready to use the Docker CLI to scale the number of containers in the service. Containers running in a service are called “tasks.”Run the following command to change the desired state of the service running in the swarm:
$ docker service scale <SERVICE-ID>=<NUMBER-OF-TASKS>
For example, start 5 instences of the helloworld sevices:
$ docker service scale helloworld=5 # start 5 instances. you can change it later.
helloworld 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
Run docker service ps <SERVICE-ID> to see the updated task list:
$ docker service ps helloworld
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
roelhski88xz helloworld.1 alpine:latest node1 Running Running 10 minutes ago
6o4ts34bmttp helloworld.2 alpine:latest node1 Running Running about a minute ago
7amy0pz964ww helloworld.3 alpine:latest node1 Running Running about a minute ago
zo9ju37c68ef helloworld.4 alpine:latest node1 Running Running about a minute ago
7wnp0v2l0vk1 helloworld.5 alpine:latest node1 Running Running about a minute ago
Run docker ps to see the containers running on the node where you’re connected. The following example shows the tasks running on manager1:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
fa05e955ff53 alpine:latest "ping docker.com" 2 minutes ago Up 2 minutes helloworld.3.7amy0pz964ww9hfiu2qsyq0uu
40a365af4a57 alpine:latest "ping docker.com" 2 minutes ago Up 2 minutes helloworld.2.6o4ts34bmttpaa44qwhkqdxpr
86ec03252986 alpine:latest "ping docker.com" 2 minutes ago Up 2 minutes helloworld.4.zo9ju37c68efkpn42ltfy7omv
f896f9b7820d alpine:latest "ping docker.com" 2 minutes ago Up 2 minutes helloworld.5.7wnp0v2l0vk140c16vztmqegl
70038e250789 alpine:latest "ping docker.com" 11 minutes ago Up 11 minutes helloworld.1.roelhski88xzkfwfr6v5r0egv
If you want to see the containers running on other nodes, ssh into those nodes and run the docker ps command.
Delete the service running on the swarm
The remaining steps in the tutorial don’t use the helloworld service, so now you can delete the service from the swarm.Run docker service rm helloworld to remove the helloworld service.
$ docker service rm helloworld
helloworld
Run docker service inspect <SERVICE-ID> to verify that the swarm manager removed the service. The CLI returns a message that the service is not found:
$ docker service inspect helloworld
[]
Status: Error: no such service: helloworld, Code: 1
Even though the service no longer exists, the task containers take a few seconds to clean up. You can use docker ps on the nodes to verify when the tasks have been removed.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS
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