Retrieving the Service Instance with the JSON Protocol

ServiceInstance is a singleton managed object that acts as a gateway to the resources available on the server. You can locate other important singletons such as SessionManager and SearchIndex from ServiceInstance properties. ServiceInstance is accessible without authentication, so you can retrieve a reference to the SessionManager which you can use to authenticate a session.

To retrieve the properties of the ServiceInstance managed object, do the following.

Prerequisites

You need the IP address or FQDN of a vCenter Server to which you will send the request.

Procedure

1. Synthesize a managed object reference to the ServiceInstance managed object. This managed object reference always has a fixed value of {type: "ServiceInstance", value: "ServiceInstance"} because it is a prerequisite for access to other managed object references.

   motype = 'ServiceInstance'
   moid = 'ServiceInstance'
   moref = motype + '/' + moid
2. Specify the property to retrieve from the managed object.

   property = 'content'

3. Assemble the URL from the pieces previously defined.

   scheme = 'https://'
   domain = 'vc.example.com'
   endpoint = '/sdk/vim25'
   version = '8.0.3'
   url = scheme + domain + endpoint + '/' + version + '/' + moref + '/' + property
   print(url)

   href="https://vc.example.com/sdk/vim25/8.0.3/ServiceInstance/ServiceInstance/content"

4. Send the URL in an HTTP GET request.

   from urllib.request import urlopen, Request
   import ssl
   # Skip certificate verification on test systems only:
   unverified_context = ssl._create_unverified_context()
   request = Request( url, headers=headers or {} )
   with urlopen( request, context=unverified_context ) as response :
     response_headers = response.headers
     response_body = response.read()

5. Display the result of the query.

   from pprint import pprint
   json_body = json.loads(response_body)
   pprint(json_body)

Results

The program displays a number of managed object references for singletons that you can use for additional requests. The following excerpt includes several important managed objects that you will use for basic operations, including authentication.

Example: Excerpt from Service Content

...
'propertyCollector': {'_typeName': 'ManagedObjectReference',
                      'type': 'PropertyCollector',
                      'value': 'propertyCollector'},
'rootFolder': {'_typeName': 'ManagedObjectReference',
               'type': 'Folder',
               'value': 'group-d1'},
'scheduledTaskManager': {'_typeName': 'ManagedObjectReference',
                         'type': 'ScheduledTaskManager',
                         'value': 'ScheduledTaskManager'},
'searchIndex': {'_typeName': 'ManagedObjectReference',
                'type': 'SearchIndex',
                'value': 'SearchIndex'},
'serviceManager': {'_typeName': 'ManagedObjectReference',
                   'type': 'ServiceManager',
                   'value': 'ServiceMgr'},
'sessionManager': {'_typeName': 'ManagedObjectReference',
                   'type': 'SessionManager',
                   'value': 'SessionManager'},
...

What to do next

Use the SessionManager URL in the Service Content to open an authenticated session with the vCenter Server instance.