Let's assume there is one application server serving x amount of clients. If the intention is to serve twice the amount of clients, you could increase the resources on the server load balancing the first server. However you go about this process, it is a repetitive manual process, because as the need increases, you will need to increase the cluster by adding application servers.
- Container lifecycle automation
- Ease of scaling out/in/up/down
- Ensuring re-creation of failed containers
- Replacement of containers without downtime (aka "blue/green deploy")
- Docker Swarm mode overview: https://docs.docker.com/engine/swarm/
- Swarm mode key concepts: https://docs.docker.com/engine/swarm/key-concepts/
Swarm is the cluster management and orchestration tooling built into Docker that essentially solves these problems. It is build using swarmkit, which implements the orchestration layer that is utilized directly inside Docker.
- Consists of multiple Docker hosts running in swarm mode and act as managers and workers
- Docker host can be a manager, worker, or both
- When creating the service, you define its optimal state (e.g. number of replicas, network and storage resources, ports exposed, etc.)
- Docker is responsible for maintaining the desired state -- if a worker node becomes unavailable, Docker schedules that node's tasks on other nodes
- A task is a running container belonging to the swarm service managed by the swarm manager, as opposed to a standalone container
A key advantage of swarm services vs. standalone containers is the pattern known as "blue/green deploy." Let's assume you modify a service's configuration -- networks and volumes connected to it as well. Docker will update the configuration, stop the service tasks with the out-of-date configuration, and create new ones with the desired state.
More about Desired state reconciliation from the Swarm mode overview Feature highlights:
Desired state reconciliation: The swarm manager node constantly monitors the cluster state and reconciles any differences between the actual state and your expressed desired state. For example, if you set up a service to run 10 replicas of a container, and a worker machine hosting two of those replicas crashes, the manager creates two new replicas to replace the replicas that crashed. The swarm manager assigns the new replicas to workers that are running and available.
- A node is an instance of the Docker engine participating in the swarm
- One or more nodes can be run on a single physical computer or cloud server; however, production deployments typically include nodes distributed across multiple physical and cloud machines
- Deploying an application to a swarm requires the submission of a service definition to a manager node. The manager node dispatches units of work called tasks to worker nodes
- Manager nodes perform orchestration and cluster management to maintain the desired state of the swarm, and elect a single leader to conduct orchestration
- Worker nodes receive and execute tasks dispatched from manager nodes
- Manager nodes also run services as worker nodes (by default), but can be configured to run manager tasks exclusively and be manager-only nodes
- An agent runs on the worker nodes and reports on the tasks assigned to it
- The worker node notifies the manager node of the current state of those tasks so the manager can handle the desired state of each worker
- A service defines the tasks to execute on the manager or worker nodes
- When creating a service, the container image is specified, along with which commands to execute inside running containers (e.g.
docker service create alpine ping 8.8.8.8) - A replicated service is a scalable service instance in which the swarm manager distributes a defined number of replica tasks among the nodes based on the scale of the desired state (e.g.
docker service create --name hello --replicas 3 --publish 8080:80 nginx) - A task carries a container along with its commands to run within the container
- Manager nodes assign tasks to work nodes based on the number of replicas set in the service scale
- Tasks are immovable from one node to another once assigned
- The swarm manager uses ingress load balancing to expose the services you want externally available to the swarm
- Manager can auto-assign the service a PublishedPort in the
30000-32767range, or it can be self-configured with any unused port - External components (i.e. cloud load balancers) are able to access the service on the PublishedPort of any node within the cluster regardless of whether or not the node is currently running the service's task
- All nodes in the swarm route ingress connections to a running task instance
- Swarm mode has internal DNS that automatically assigns each service a DNS entry
- The swarm manager uses internal load balancing to distribute requests among services within the cluster based on the DNS name of the service
- Not enabled by default
- When running
docker swarm init, the Docker Engine sets up the swarm by:- enabling swarm
- creating a
defaultswarm - designating the current node as a leader manager
- naming the node with the machine hostname
- configuring the manager to listen on the active network interface on port 2377
- setting the current node to
Activeavailability, allowing it to receive tasks from the scheduler - starting an internal distributed data store to maintain view consistency between services and any Engines participating in the swarm
- generates a self-signed root CA, by default
- generates tokens for worker and manager nodes to join the swarm, be default
- creates an overlay network name
ingressfor publishing external service ports
$ docker swarm init
Swarm initialized: current node (dxn1zf6l61qsb1josjja83ngz) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join \
--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
192.168.99.100:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.Manager nodes utilize and advertise address to allow other nodes within the swarm to access the Swarmkit API and overlay networking. The other nodes must be able to access the manager node on its advertise address as well.
Without a specified advertise address, Docker will try to use the IP address listening on 2377 by default. If the system has multiple IP addresses, you must specify the correct --advertise-addr to enable inter-manager communication and overlay networking:
$ docker swarm init --advertise-addr <MANAGER-IP>An example of this configuration is show in the demo being utilized in play.docker.com.
Nodes require a secret token to join a swarm. The token for worker nodes and manager nodes are not the same. Nodes only use the join-token at the moment they join the swarm. Rotating the token after joining does not affect a node's swarm membership. Rotation of a token ensures an old token cannot be used by new nodes attempting to join.
To retrieve the join command with the join token for work nodes:
$ docker swarm join-token worker
To add a worker to this swarm, run the following command:
docker swarm join \
--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
192.168.99.100:2377
This node joined a swarm as a worker.To view the join command and token for manager nodes:
$ docker swarm join-token manager
To add a worker to this swarm, run the following command:
docker swarm join \
--token SWMTKN-1-59egwe8qangbzbqb3ryawxzk3jn97ifahlsrw01yar60pmkr90-bdjfnkcflhooyafetgjod97sz \
192.168.99.100:2377Pass the --quiet flag to print the token only:
$ docker swarm join-token --quiet worker
SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7cFor more information on Swarm mode, the Docker docs are your friend.
- Use play.docker.com
- Single instance for basic examples
- 3-node swarm
- Swarm Visualizer
Note: Could copy/paste the docker swarm join --token <token>, or get it later as needed.
$ docker swarm init --advertise-addr <instance IP>
Swarm initialized: current node (98bw7xv33ryx0yzb05gksfiny) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-5836ufdx8zspdccpirb3ezizt7eglbebqhapnzs4fikysl2pa3-36bcaxewlzgrxxv0enah0lg26 192.168.0.48:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.$ docker service create --name hello --replicas 3 --publish 8080:80 nginx
4zmjjn3ns97pm9v32zxtkb2y9
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
98bw7xv33ryx0yzb05gksfiny * node1 Ready Active Leader 18.03.1-ce$ docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
4zmjjn3ns97p hello replicated 3/3 nginx:latest *:8080->80/tcp# $ docker service ps [ID/NAME]
$ docker service ps hello
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
nyg72k0vw2kt hello.1 nginx:latest node1 Running Running 10 minutes ago
kwqqd7g4nwlv hello.2 nginx:latest node1 Running Running 10 minutes ago
qg0s1ooo3172 hello.3 nginx:latest node1 Running Running 10 minutes ago$ docker service create alpine ping 8.8.8.8
gz7521yo6tb4ocg2k5hlrcbb0
overall progress: 1 out of 1 tasks
1/1: running [==================================================>]
verify: Service converged$ docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
4zmjjn3ns97p hello replicated 3/3 nginx:latest *:8080->80/tcp
gz7521yo6tb4 relaxed_golick replicated 1/1 alpine:latest# $ docker service ps [ID/NAME]
$ docker service ps relaxed_golick
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
558e3zecikqt relaxed_golick.1 alpine:latest node1 Running Running 4 minutes ago# $ docker service update <ID> --replicas <NUM>
$ docker service update gz7521yo6tb4 --replicas 3
gz7521yo6tb4
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged$ docker swarm --help
Usage: docker swarm COMMAND
Manage Swarm
Options:
Commands:
ca Display and rotate the root CA
init Initialize a swarm
join Join a swarm as a node and/or manager
join-token Manage join tokens
leave Leave the swarm
unlock Unlock swarm
unlock-key Manage the unlock key
update Update the swarm
Run 'docker swarm COMMAND --help' for more information on a command.
$ docker update --help
Usage: docker update [OPTIONS] CONTAINER [CONTAINER...]
Update configuration of one or more containers
Options:
--blkio-weight uint16 Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0)
--cpu-period int Limit CPU CFS (Completely Fair Scheduler) period
--cpu-quota int Limit CPU CFS (Completely Fair Scheduler) quota
--cpu-rt-period int Limit the CPU real-time period in microseconds
--cpu-rt-runtime int Limit the CPU real-time runtime in microseconds
-c, --cpu-shares int CPU shares (relative weight)
--cpus decimal Number of CPUs
--cpuset-cpus string CPUs in which to allow execution (0-3, 0,1)
--cpuset-mems string MEMs in which to allow execution (0-3, 0,1)
--kernel-memory bytes Kernel memory limit
-m, --memory bytes Memory limit
--memory-reservation bytes Memory soft limit
--memory-swap bytes Swap limit equal to memory plus swap: '-1' to enable unlimited swap
--restart string Restart policy to apply when a container exits
$ docker service update --help # blue/green
Usage: docker service update [OPTIONS] SERVICE
Update a service
Options:
--args command Service command args
--config-add config Add or update a config file on a service
--config-rm list Remove a configuration file
--constraint-add list Add or update a placement constraint
--constraint-rm list Remove a constraint
--container-label-add list Add or update a container label
--container-label-rm list Remove a container label by its key
--credential-spec credential-spec Credential spec for managed service account (Windows only)
-d, --detach Exit immediately instead of waiting for the service to converge
--dns-add list Add or update a custom DNS server
--dns-option-add list Add or update a DNS option
--dns-option-rm list Remove a DNS option
--dns-rm list Remove a custom DNS server
--dns-search-add list Add or update a custom DNS search domain
--dns-search-rm list Remove a DNS search domain
--endpoint-mode string Endpoint mode (vip or dnsrr)
--entrypoint command Overwrite the default ENTRYPOINT of the image
--env-add list Add or update an environment variable
--env-rm list Remove an environment variable
--force Force update even if no changes require it
--generic-resource-add list Add a Generic resource
--generic-resource-rm list Remove a Generic resource
--group-add list Add an additional supplementary user group to the container
--group-rm list Remove a previously added supplementary user group from the container
--health-cmd string Command to run to check health
--health-interval duration Time between running the check (ms|s|m|h)
--health-retries int Consecutive failures needed to report unhealthy
--health-start-period duration Start period for the container to initialize before counting retries towards unstable (ms|s|m|h)
--health-timeout duration Maximum time to allow one check to run (ms|s|m|h)
--host-add list Add a custom host-to-IP mapping (host:ip)
--host-rm list Remove a custom host-to-IP mapping (host:ip)
--hostname string Container hostname
--image string Service image tag
--isolation string Service container isolation mode
--label-add list Add or update a service label
--label-rm list Remove a label by its key
--limit-cpu decimal Limit CPUs
--limit-memory bytes Limit Memory
--log-driver string Logging driver for service
--log-opt list Logging driver options
--mount-add mount Add or update a mount on a service
--mount-rm list Remove a mount by its target path
--network-add network Add a network
--network-rm list Remove a network
--no-healthcheck Disable any container-specified HEALTHCHECK
--no-resolve-image Do not query the registry to resolve image digest and supported platforms
--placement-pref-add pref Add a placement preference
--placement-pref-rm pref Remove a placement preference
--publish-add port Add or update a published port
--publish-rm port Remove a published port by its target port
-q, --quiet Suppress progress output
--read-only Mount the containers root filesystem as read only
--replicas uint Number of tasks
--reserve-cpu decimal Reserve CPUs
--reserve-memory bytes Reserve Memory
--restart-condition string Restart when condition is met ("none"|"on-failure"|"any")
--restart-delay duration Delay between restart attempts (ns|us|ms|s|m|h)
--restart-max-attempts uint Maximum number of restarts before giving up
--restart-window duration Window used to evaluate the restart policy (ns|us|ms|s|m|h)
--rollback Rollback to previous specification
--rollback-delay duration Delay between task rollbacks (ns|us|ms|s|m|h)
--rollback-failure-action string Action on rollback failure ("pause"|"continue")
--rollback-max-failure-ratio float Failure rate to tolerate during a rollback
--rollback-monitor duration Duration after each task rollback to monitor for failure (ns|us|ms|s|m|h)
--rollback-order string Rollback order ("start-first"|"stop-first")
--rollback-parallelism uint Maximum number of tasks rolled back simultaneously (0 to roll back all at once)
--secret-add secret Add or update a secret on a service
--secret-rm list Remove a secret
--stop-grace-period duration Time to wait before force killing a container (ns|us|ms|s|m|h)
--stop-signal string Signal to stop the container
-t, --tty Allocate a pseudo-TTY
--update-delay duration Delay between updates (ns|us|ms|s|m|h)
--update-failure-action string Action on update failure ("pause"|"continue"|"rollback")
--update-max-failure-ratio float Failure rate to tolerate during an update
--update-monitor duration Duration after each task update to monitor for failure (ns|us|ms|s|m|h)
--update-order string Update order ("start-first"|"stop-first")
--update-parallelism uint Maximum number of tasks updated simultaneously (0 to update all at once)
-u, --user string Username or UID (format: <name|uid>[:<group|gid>])
--with-registry-auth Send registry authentication details to swarm agents
-w, --workdir string Working directory inside the container# $ docker container rm -f <NAME>.1.<ID>
$ docker container ls # <NAMES> field
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8fa7faa344e3 alpine:latest "ping 8.8.8.8" 8 minutes ago Up 8 minutes relaxed_golick.3.plzginj3y2bersge03ip91k1o
aa90115a6375 alpine:latest "ping 8.8.8.8" 8 minutes ago Up 8 minutes relaxed_golick.2.ra9byjbz0ah8y6linvozx8cnh
0dd2d231ecd3 alpine:latest "ping 8.8.8.8" 16 minutes ago Up 16 minutes relaxed_golick.1.558e3zecikqtbump1t2oblcoi
6a46e803dc8e nginx:latest "nginx -g 'daemon of…" 38 minutes ago Up 38 minutes 80/tcp hello.2.kwqqd7g4nwlv58vltszx5qwk8
62f1626710df nginx:latest "nginx -g 'daemon of…" 38 minutes ago Up 38 minutes 80/tcp hello.3.qg0s1ooo3172rzaa0ab18fe58
b25c2de42e50 nginx:latest "nginx -g 'daemon of…" 38 minutes ago Up 38 minutes 80/tcp hello.1.nyg72k0vw2ktrw0wlbc5jbzix
$ docker container rm -f hello.1.nyg72k0vw2ktrw0wlbc5jbzix
hello.1.nyg72k0vw2ktrw0wlbc5jbzix
$ docker service ls # if you're quick enough, shows 2/3 services
ID NAME MODE REPLICAS IMAGE PORTS
4zmjjn3ns97p hello replicated 2/3 nginx:latest *:8080->80/tcp
gz7521yo6tb4 relaxed_golick replicated 3/3 alpine:latest
$ docker service ls # relaunches a new replacement services within seconds
ID NAME MODE REPLICAS IMAGE PORTS
4zmjjn3ns97p hello replicated 3/3 nginx:latest *:8080->80/tcp
gz7521yo6tb4 relaxed_golick replicated 3/3 alpine:latest
$ docker service ps hello # historical representation of task
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
teklprpfs5w0 hello.1 nginx:latest node1 Running Running 3 minutes ago
nyg72k0vw2kt \_ hello.1 nginx:latest node1 Shutdown Failed 3 minutes ago "task: non-zero exit (137)"
kwqqd7g4nwlv hello.2 nginx:latest node1 Running Running 43 minutes ago
qg0s1ooo3172 hello.3 nginx:latest node1 Running Running 43 minutes ago$ docker service rm hello
hello
$ docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
gz7521yo6tb4 relaxed_golick replicated 3/3 alpine:latest
$ docker container ls # sometimes lags in the orchestration queue
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8fa7faa344e3 alpine:latest "ping 8.8.8.8" 15 minutes ago Up 15 minutes relaxed_golick.3.plzginj3y2bersge03ip91k1o
aa90115a6375 alpine:latest "ping 8.8.8.8" 15 minutes ago Up 15 minutes relaxed_golick.2.ra9byjbz0ah8y6linvozx8cnh
0dd2d231ecd3 alpine:latest "ping 8.8.8.8" 23 minutes ago Up 23 minutes relaxed_golick.1.558e3zecikqtbump1t2oblcoi# node1
$ docker swarm init --advertise-addr <instance IP>
Swarm initialized: current node (j3yr0m1vlv6kcyqy8qige7xlq) is now a manager.
To add a worker to this swarm, run the following command:
docker swarm join --token SWMTKN-1-0qqupobcvwq9bxowqyf0smmdyx3tv6qfmehv8kptaauv00f8c9-512s10jh07e300inyb3x41wwr 192.168.0.48:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
# copy-paste join-token to node2
$ docker swarm join --token SWMTKN-1-0qqupobcvwq9bxowqyf0smmdyx3tv6qfmehv8kptaauv00f8c9-512s10jh07e300inyb3x41wwr 192.168.0.48:2377
This node joined a swarm as a worker.
# node1: lists nodes with node1 manager status as "Leader"
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
j3yr0m1vlv6kcyqy8qige7xlq * node1 Ready Active Leader 18.03.1-ce
my0nswmsmc2pq45vqs33hq5o8 node2 Ready Active 18.03.1-ce
# node2: not a manager, can't do manager things
$ docker node ls
Error response from daemon: This node is not a swarm manager. Worker nodes cant be used to view or modify cluster state. Please run this command on a manager node or promote the current node to a manager.
# node1: update node2 to be a manager
$ docker node update --role manager node2
node2
# node2: lists nodes with node1 manager status as "Leader" and node2 manager status as "Reachable"
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
j3yr0m1vlv6kcyqy8qige7xlq node1 Ready Active Leader 18.03.1-ce
my0nswmsmc2pq45vqs33hq5o8 * node2 Ready Active Reachable 18.03.1-ce
# node1: get the join-token to add node3
$ docker swarm join-token manager
To add a manager to this swarm, run the following command:
docker swarm join --token SWMTKN-1-0qqupobcvwq9bxowqyf0smmdyx3tv6qfmehv8kptaauv00f8c9-9ar6jnhoswqgx6oqzdztbqaag 192.168.0.48:2377
# node3: paste join-token
$ docker swarm join --token SWMTKN-1-0qqupobcvwq9bxowqyf0smmdyx3tv6qfmehv8kptaauv00f8c9-9ar6jnhoswqgx6oqzdztbqaag 192.168.0.48:2377
This node joined a swarm as a manager.
# node1: list nodes with node1 manager status as "Leader", and node2 and node3 manager statuses as "Reachable"
$ docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
j3yr0m1vlv6kcyqy8qige7xlq * node1 Ready Active Leader 18.03.1-ce
my0nswmsmc2pq45vqs33hq5o8 node2 Ready Active Reachable 18.03.1-ce
wjdr1inb3ahcc7uyygqwokl2o node3 Ready Active Reachable 18.03.1-ce
# node1: create replicated swarm with 3 replicas using alpine image with the command to ping Google's DNS service (8.8.8.8)
$ docker service create --replicas 3 alpine ping 8.8.8.8
c6dx9i1x45crf429s44a87fs4
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged
# node1: list the service tasks currently running on the outputted container
$ docker node ps
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
t1o7m94rdzng gifted_blackwell.1 alpine:latest node1 Running Running about a minute ago
# node1: show containers running on node2
$ docker node ps node2
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
liwv1yjog5i7 gifted_blackwell.2 alpine:latest node2 Running Running 2 minutes ago
# node1: list all tasks running, their current state, etc.
$ docker service ps gifted_blackwell
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
t1o7m94rdzng gifted_blackwell.1 alpine:latest node1 Running Running 3 minutes ago
liwv1yjog5i7 gifted_blackwell.2 alpine:latest node2 Running Running 3 minutes ago
jo7te1cofmkd gifted_blackwell.3 alpine:latest node3 Running Running 3 minutes ago
# node1: scale the service
# $ docker service scale <SERVICE-ID>=<NUMBER>
$ docker service scale gifted_blackwell=5
gifted_blackwell 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
# node1: list updated running tasks to see the scaled state
$ docker service ps gifted_blackwell
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
t1o7m94rdzng gifted_blackwell.1 alpine:latest node1 Running Running 9 minutes ago
liwv1yjog5i7 gifted_blackwell.2 alpine:latest node2 Running Running 9 minutes ago
jo7te1cofmkd gifted_blackwell.3 alpine:latest node3 Running Running 9 minutes ago
pn3fp4he6468 gifted_blackwell.4 alpine:latest node2 Running Running about a minute ago
4i9won9100b1 gifted_blackwell.5 alpine:latest node1 Running Running about a minute ago
# node1: list running containers on the connected node
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6d2325535e5d alpine:latest "ping 8.8.8.8" 2 minutes ago Up 2 minutes gifted_blackwell.5.4i9won9100b1t01xbh3wyl0le
bacc7f5b4603 alpine:latest "ping 8.8.8.8" 10 minutes ago Up 10 minutes gifted_blackwell.1.t1o7m94rdzngo36sre8ojeje7https://github.com/BretFisher/docker-swarm-visualizer
https://hub.docker.com/r/bretfisher/visualizer/
Demo container that displays Docker services running on a Docker Swarm in a diagram.
This works only with Docker swarm mode which was introduced in Docker 1.12. These instructions presume you are running on the master node and you already have a Swarm running.
Each node in the swarm will show all tasks running on it. When a service goes down it'll be removed. When a node goes down it won't, instead the circle at the top will turn red to indicate it went down. Tasks will be removed.
Occasionally the Remote API will return incomplete data, for instance the node can be missing a name. The next time info for that node is pulled, the name will update.
# node1: pull bretfisher/visualizer from Docker Hub
$ docker pull bretfisher/visualizer
Using default tag: latest
latest: Pulling from bretfisher/visualizer
88286f41530e: Pull complete
6a722742375f: Pull complete
7e9d2f284de4: Pull complete
da2fce695ca7: Pull complete
7465a3d10f0c: Pull complete
2b6c40acc71a: Pull complete
d00de06f06cc: Pull complete
0efb3b62dcd6: Pull complete
c6bbd7fdfa8b: Pull complete
fd9a75018b5a: Pull complete
1c6b95e5ce5e: Pull complete
713a6496787e: Pull complete
1b16a276e6da: Pull complete
Digest: sha256:479eb1f494e86a83c29a49ef9e763fde09490f1d4a8f1890808bd8fed8485de3
Status: Downloaded newer image for bretfisher/visualizer:latest
# node1: run in docker swarm
$ docker service create \
--name=viz \
--publish=8080:8080/tcp \
--constraint=node.role==manager \
--mount=type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock \
dockersamples/visualizer
3gq3nyblr0va7gjfm65vgp4to
overall progress: 1 out of 1 tasks
1/1: running [==================================================>]
verify: Service converged