Docker Service Modes

Service Modes:

1. Notice it in docker service ls
2. Defaults to replicated, but global is an option.
3. Global=one task per node
4. Set on service create only, must remove service to change.
5. Good for host agents (security, monitoring, backup, proxy, etc).
6. Global Mode can be combined with constraints. (version 1.13+)

Replicated v/s global services:

There are two types of service deployments, replicated and global.

For a replicated service, you specify the number of identical tasks you want to run. For example, you decide to deploy an HTTP service with three replicas, each serving the same content.

A global service is a service that runs one task on every node. There is no pre-specified number of tasks. Each time you add a node to the swarm, the orchestrator creates a task and the scheduler assigns the task to the new node. Good candidates for global services are monitoring agents, an anti-virus scanners or other types of containers that you want to run on every node in the swarm.


[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app
$ docker service create --mode=global --name=test1 nginx
u2dxb2rmibqce20eg40gcqs9o
overall progress: 4 out of 4 tasks
przg4018ytv0: running   [==================================================>]
epr99u2uuky4: running   [==================================================>]
ptncdjhii2as: running   [==================================================>]
khlavmixa3pv: running   [==================================================>]
verify: Service converged

[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app
$ docker service ls
ID                  NAME                 MODE                REPLICAS            IMAGE                             PORTS
u2dxb2rmibqc        test1                global              4/4                 nginx:latest                     
q9vom02oh95n        voteapp_visualizer   replicated          1/1                 dockersamples/visualizer:stable   *:8080->8080/tcp
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service ps test1
ID                  NAME                              IMAGE               NODE                DESIRED STATE       CURRENT STATE           
ERROR               PORTS
1vfev5nr30mh        test1.przg4018ytv0ksr3fqsvvkcst   nginx:latest        node4               Running             Running 31 seconds ago 
                   
dgk73ddgd6im        test1.epr99u2uuky4temuxydo1j98x   nginx:latest        node3               Running             Running 31 seconds ago 
                   
129pvl9sspag        test1.khlavmixa3pvam8x8okpiv84v   nginx:latest        node2               Running             Running 31 seconds ago 
                   
ov2k20yegep0        test1.ptncdjhii2as07utv3m51a6zr   nginx:latest        node1               Running             Running 30 seconds ago                     
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app
$
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app
$

[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service rm test1
test1
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service ls
ID                  NAME                 MODE                REPLICAS            IMAGE                             PORTS
q9vom02oh95n        voteapp_visualizer   replicated          1/1                 dockersamples/visualizer:stable   *:8080->8080/tcp
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service create --mode=global --name=test1 --constraint=node.role==worker nginx
8i78qliotelyddf5l7kgc7hwt
overall progress: 3 out of 3 tasks
przg4018ytv0: running   [==================================================>]
khlavmixa3pv: running   [==================================================>]
epr99u2uuky4: running   [==================================================>]
verify: Service converged

[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service ls
ID                  NAME                 MODE                REPLICAS            IMAGE                             PORTS
8i78qliotely        test1                global              3/3                 nginx:latest                     
q9vom02oh95n        voteapp_visualizer   replicated          1/1                 dockersamples/visualizer:stable   *:8080->8080/tcp
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app

$ docker service ps test1
ID                  NAME                              IMAGE               NODE                DESIRED STATE       CURRENT STATE            ERROR               PORTS
lnu4c4mxrftk        test1.przg4018ytv0ksr3fqsvvkcst   nginx:latest        node4               Running             Running 33 seconds ago                     
jg75f1seauxg        test1.epr99u2uuky4temuxydo1j98x   nginx:latest        node3               Running             Running 33 seconds ago                     
6loqrzvminzx        test1.khlavmixa3pvam8x8okpiv84v   nginx:latest        node2               Running             Running 33 seconds ago                     
[node1] (local) root@192.168.0.48 ~/voting-app/example-voting-app
$