moby/docs/swarm/swarm-tutorial/inspect-service.md

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.

1. 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.

2. 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:

   $ docker service inspect --pretty helloworld
   
   ID:     2zs4helqu64f3k3iuwywbk49w
   Name:       helloworld
   Mode:       REPLICATED
    Scale: 1
   Placement:
    Strategy:  SPREAD
   UpdateConfig:
    Parallelism:   1
   ContainerSpec:
    Image:     alpine
    Command:   ping docker.com
   

   Tip: To return the service details in json format, run the same command without the --pretty flag.

   $ docker service inspect helloworld
   [
   {
       "ID": "2zs4helqu64f3k3iuwywbk49w",
       "Version": {
           "Index": 16264
       },
       "CreatedAt": "2016-06-06T17:41:11.509146705Z",
       "UpdatedAt": "2016-06-06T17:41:11.510426385Z",
       "Spec": {
           "Name": "helloworld",
           "ContainerSpec": {
               "Image": "alpine",
               "Command": [
                   "ping",
                   "docker.com"
               ],
               "Resources": {
                   "Limits": {},
                   "Reservations": {}
               }
           },
           "Mode": {
               "Replicated": {
                   "Instances": 1
               }
           },
           "RestartPolicy": {},
           "Placement": {},
           "UpdateConfig": {
               "Parallelism": 1
           },
           "EndpointSpec": {}
       },
       "Endpoint": {
           "Spec": {}
       }
   }
   ]
   

3. Run docker service tasks <SERVICE-ID> to see which nodes are running the service:

   $ docker service tasks helloworld
   
   ID                         NAME          SERVICE     IMAGE   DESIRED STATE  LAST STATE          NODE
   1n6wif51j0w840udalgw6hphg  helloworld.1  helloworld  alpine  RUNNING        RUNNING 19 minutes  manager1
   

   In this case, the one instance of the helloworld service is running on the manager1 node. Manager nodes in a Swarm can execute tasks just like worker nodes.

   Swarm also shows you the DESIRED STATE and LAST STATE of the service task so you can see if tasks are running according to the service definition.

4. Run docker ps on the node where the instance of the service is running to see the service container.

   Tip: If helloworld is running on a node other than your manager node, you must ssh to that node.

   $docker ps
   
   CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
   a0b6c02868ca        alpine:latest       "ping docker.com"   12 minutes ago      Up 12 minutes                           helloworld.1.1n6wif51j0w840udalgw6hphg
   

What's next?

Next, you can change the scale for the service running in the Swarm.