Docker Swarm managers acting nodes?
<p>I've created setup with 3 swarm managers and 3 nodes.</p>

<p>You e can see below that in the case with 3 masters and 3 workers actually I have <strong>3 managers and 6 nodes</strong>. Is it idea that managers are also capable to run containers, not just workers? Am I missing something in the setup or this is intended to work  as it is now?</p>

<p>when I execute docker info command, I am getting this output:</p>

<pre><code>ubuntu@manager3:~$ docker info
Containers: 4
 Running: 3
 Paused: 0
 Stopped: 1
Images: 3
Server Version: 1.12.0
Storage Driver: aufs
 Root Dir: /var/lib/docker/aufs
 Backing Filesystem: extfs
 Dirs: 23
 Dirperm1 Supported: false
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: overlay bridge host null
Swarm: active
 NodeID: 9uv3xhwzibx52xghpsa0sp3f7
 Is Manager: true
 ClusterID: 04r095rvj6b4i7ygbnr2quo9e
 **Managers: 3
 Nodes: 6**
 Orchestration:
  Task History Retention Limit: 5
 Raft:
  Snapshot interval: 10000
  Heartbeat tick: 1
  Election tick: 3
 Dispatcher:
  Heartbeat period: 5 seconds
 CA configuration:
  Expiry duration: 3 months
 Node Address: 172.100.0.23
Runtimes: runc
Default Runtime: runc
Security Options: apparmor
Kernel Version: 3.13.0-92-generic
Operating System: Ubuntu 14.04.4 LTS
OSType: linux
Architecture: x86_64
CPUs: 1
Total Memory: 992.5 MiB
Name: manager3
ID: MUXB:GUNV:HIDO:APRJ:S2JU:763E:QSOL:2554:EZJL:L4OI:6TS5:RD7O
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
WARNING: No swap limit support
Insecure Registries:
 127.0.0.0/8
</code></pre>

<p>when I create some services to run on swarm cluster:</p>

<p><code>docker service create --replicas=3 --name redis redis:latest</code></p>

<p>Some of them will run on managers, some on workers. That's confusing me.</p>

<p>if I create more services</p>

<p><code>docker service create --replicas=6 --name redis redis:latest</code></p>

<p>they will run on all machines in cluster. increasing even more will start failing due to port collision. </p>