The Creator Supreme! …..or How to be the Kenny Dalglish of Nutanix API automation

For the non European football fans out there, Kenny Dalglish,or “King Kenny” as he was known to both the Liverpool and Celtic faithful, was once described in a match commentary as “the creator supreme”.  In this short series of posts covering the REST capabilities for managing the Nutanix Enterprise Cloud, I hope to show its possible that we can all be a “creator supreme” just like King Kenny!

Swagger

The first place to look when working with the API is the REST API Explorer itself. You invoke the Explorer page by right-clicking the admin pull-down menu (top right of Prism home page) and selecting the REST API Explorer option.

It’s good practice to create a separate user login for the REST Explorer. The REST API Explorer is essentially the documentation to the API. It’s produced via swagger, which is an open standard that takes your API spec and generates interactive documentation. The documentation can be viewed and you are able to interactively test API calls via a browser.

Images

Let’s start by taking a look at a simple POST method that will list all currently available images:

POST /images/list

Select the above method in the images section of the REST API Explorer to expand the method details:

In order to try out the REST method, double click on the Model Schema box (right hand side above) – this will then be populated into the get_entities_request box on the left hand side. You can edit the entities according to how you want to retrieve the available information. For example here’s the bare minimum you need as a JSON payload to request information from the Images catalogue.

 {
   "kind": "image",
   "offset": 0,
   "length": 10
 }

Note that with our pagination we are starting at offset zero – so the first image – until the tenth image, defined by the length parameter. With the JSON payload entered as above we can press the Try it out! button and see the method in action.

The results of the method call are displayed below. The Curl syntax for invoking the method and json payload are shown, along with the individual Request URL and the Response Body. We can use the Curl syntax to programmatically call the method outside of the Explorer, either in Bash or Python, for example.

Once we begin to use the methods independently of the Explorer, then in addition to curl you should consider installing a JSON command line processor like jq, and use a JSON Linter to validate your JSON syntax for data payloads. How the tools might be used will be shown throughout this post

CURL

Lets recap the previous POST method but this time run it from the command line. In this instance we load the JSON payload (see above) from the file list_images_v3.json using the -d option. The -k option , or — insecure allows the command to proceed even though I am using self-signed SSL/TLS certs. The -s option simply disables all progress indicators.

curl -s --user api:<password> -k -X POST --header "Content-Type: application/json" --header "Accept: application/json" -d @list_images_v3.json "https://10.XX.XX.60:9440/api/nutanix/v3/images/list" | jq 

Piping the output from the curl command into jq, provides a formatted and syntax highlighted output that’s easier to read. To make this more obvious, let’s use some additional options to the jq command line and pull out just one image reference:

curl -s --user apiuser:<password> -k -X POST --header "Content-Type: application/json" --header "Accept: application/json" -d @list_images_v3.json "https://10.68.64.60:9440/api/nutanix/v3/images/list" | jq '.entities[] | select (.spec.name=="CentOS7-x86_64-Generic Cloud")'

 {
   "status": {
     "state": "COMPLETE",
     "name": "CentOS7-x86_64-Generic Cloud",
     "resources": {
       "retrieval_uri_list": [
         "https://127.0.0.1:9440/api/nutanix/v3/images//file"
       ],
       "image_type": "DISK_IMAGE",
       "architecture": "X86_64",
       "size_bytes": 8589934592
     },
     "description": "Generic Cloud"
   },
   "spec": {
     "name": "CentOS7-x86_64-Generic Cloud",
     "resources": {
       "image_type": "DISK_IMAGE",
       "architecture": "X86_64"
     },
     "description": "Generic Cloud"
   },
   "metadata": {
     "last_update_time": "2019-03-27T10:47:15Z",
     "kind": "image",
     "uuid": "04a18eb0-a3ed-4ff7-aa43-bdbb055a96ef",
     "spec_version": 0,
     "creation_time": "2019-03-27T10:47:15Z",
     "categories": {}
   }
 }

All well and good if you know the exact name of your image. What about if you don’t ? See below

curl -s --user apiuser:<password> -k -X POST --header "Content-Type: application/json" --header "Accept: application/json" -d @list_images_v3.json "https://10.68.64.60:9440/api/nutanix/v3/images/list" | jq '.entities[] | select (.spec.name | . and contains("CentOS"))'

{
  "status": {
    "state": "COMPLETE",
    "name": "CentOS7-x86_64-Minimal",
    "resources": {
      "retrieval_uri_list": [
        "https://127.0.0.1:9440/api/nutanix/v3/images//file"
      ],
      "image_type": "ISO_IMAGE",
      "architecture": "X86_64",
      "size_bytes": 713031680
    },
    "description": "Minimal"
  },
  "spec": {
    "name": "CentOS7-x86_64-Minimal",
    "resources": {
      "image_type": "ISO_IMAGE",
      "architecture": "X86_64"
    },
    "description": "Minimal"
  },
  "metadata": {
    "last_update_time": "2019-03-27T10:47:15Z",
    "kind": "image",
    "uuid": "dd482003-99f4-45df-9406-1dc9859418c4",
    "spec_version": 0,
    "creation_time": "2019-03-27T10:47:15Z",
    "categories": {}
  }
}
{
  "status": {
    "state": "COMPLETE",
    "name": "CentOS7-x86_64-Generic Cloud",
    "resources": {
      "retrieval_uri_list": [
        "https://127.0.0.1:9440/api/nutanix/v3/images//file"
      ],
      "image_type": "DISK_IMAGE",
      "architecture": "X86_64",
      "size_bytes": 8589934592
    },
    "description": "Generic Cloud"
  },
  "spec": {
    "name": "CentOS7-x86_64-Generic Cloud",
    "resources": {
      "image_type": "DISK_IMAGE",
      "architecture": "X86_64"
    },
    "description": "Generic Cloud"
  },
  "metadata": {
    "last_update_time": "2019-03-27T10:47:15Z",
    "kind": "image",
    "uuid": "04a18eb0-a3ed-4ff7-aa43-bdbb055a96ef",
    "spec_version": 0,
    "creation_time": "2019-03-27T10:47:15Z",
    "categories": {}
  }
}

One of the prime uses for this kind of command is to retrieve only the info required when populating a schema for another REST method (see below shortly). For example, you may only want a subset of entries and perhaps they need to be conveniently labelled:

curl -s --user apiuser:<password> -k -X POST --header "Content-Type: application/json" --header "Accept: application/json" -d @list_images_v3.json "https://10.68.64.60:9440/api/nutanix/v3/images/list" | jq '.entities[] | {name: .spec.name, type: .spec.resources.image_type, uuid: .metadata.uuid} | select (.name | . and contains("CentOS"))'
{
"name": "CentOS7-x86_64-Minimal",
"type": "ISO_IMAGE",
"uuid": "dd482003-99f4-45df-9406-1dc9859418c4"
}
{
"name": "CentOS7-x86_64-Generic Cloud",
"type": "DISK_IMAGE",
"uuid": "04a18eb0-a3ed-4ff7-aa43-bdbb055a96ef"
}

Upload

Let’s have a look at uploading an image to the image repository on your Prism Central instance. The following is the required schema :

cat upload_image_v3.json
{
     "spec": {
         "name": "test",
         "resources": {
             "version": {
                 "product_version": "test",
                 "product_name": "test"
             },
             "architecture": "X86_64",
             "image_type": "DISK_IMAGE",
             "source_uri": "http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-disk1.img"
         }
     },
     "api_version": "3.1.0",
     "metadata": {
         "kind": "image"
     }
 }

which we can use as follows :

curl -s --user apiuser:<password> -k -X POST --header "Content-Type: application/json" --header "Accept: application/json" -d @upload_image_v3.json "https://10.68.64.60:9440/api/nutanix/v3/images" | jq .
 {
   "status": {
     "state": "PENDING",
     "execution_context": {
       "task_uuid": "f1456be3-21a8-45ab-9dc3-c323973e6f3f"
     }
   },
   "spec": {
     "name": "test",
     "resources": {
       "image_type": "DISK_IMAGE",
       "source_uri": "http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-disk1.img",
       "version": {
         "product_version": "test",
         "product_name": "test"
       },
       "architecture": "X86_64"
     }
   },
   "api_version": "3.1",
   "metadata": {
     "owner_reference": {
       "kind": "user",
       "uuid": "00000000-0000-0000-0000-000000000000",
       "name": "admin"
     },
     "kind": "image",
     "spec_version": 0,
     "uuid": "b87c7183-8716-4051-8a35-da69fdbf1e60"
   }
 }

Tasks

Notice the PENDING status in the output above. We can follow the progress of the image upload by using the task_uuid entry in a tasks method call. The call can be run again and again until a task, in this case the upload, is complete

curl -s --user apiuser:<password> -k -X GET --header "Content-Type: application/json" --header "Accept: application/json" "https://10.68.64.60:9440/api/nutanix/v3/tasks/f1456be3-21a8-45ab-9dc3-c323973e6f3f" | jq .
 {
   "status": "RUNNING",
   "last_update_time": "2019-05-30T13:19:00Z",
   "logical_timestamp": 1,
   "entity_reference_list": [
     {
       "kind": "image",
       "uuid": "b87c7183-8716-4051-8a35-da69fdbf1e60"
     }
   ],
   "start_time": "2019-05-30T13:19:00Z",
   "creation_time": "2019-05-30T13:18:59Z",
   "start_time_usecs": 1559222340033005,
   "cluster_reference": {
     "kind": "cluster",
     "uuid": "e0cca748-66c4-45fb-95e2-10836439ea15"
   },
   "subtask_reference_list": [],
   "progress_message": "create_image_intentful",
   "creation_time_usecs": 1559222339906023,
   "operation_type": "create_image_intentful",
   "percentage_complete": 0,
   "api_version": "3.1",
   "uuid": "f1456be3-21a8-45ab-9dc3-c323973e6f3f"

Delete

Finally, lets delete the image. This is done by specifying the image UUID in the delete method call. We covered how to get a UUID for an image (or any entity really) above. So let’s just show the call

curl -s --user apiuser:<password> -k -X DELETE --header "Content-Type: application/json" --header "Accept: application/json" "https://10.68.64.60:9440/api/nutanix/v3/images/081e562f-6c26-4897-bc36-a74e4843bb57" | jq .
 {
     "status": 
     {
         "state": "DELETE_PENDING", 
         "execution_context": 
             {
                 "task_uuid": "b9ae5dce-c79d-4bca-b77d-b322949f71e5"
             }
     }, 
     "spec": "", 
     "api_version": "3.1", 
     "metadata": 
         {
             "kind": "image"
         }
 }

You can of course track the deletion progress via the tasks method using the task_uuid produced above.

Conclusion

Useful Resources recap:
HTTP Response status codes 
jq
curl
JSON Lint - The JSON Validator

Hopefully this will help get people started on their API path, we haven’t really scratched the surface of what can be done. Hopefully, this post has at least demystified where and how to make a start. In subsequent posts I hope to show more ways to glean info from the API Explorer itself and how to use it to build more complex REST methods. Until then, check out Nutanix Developer Community site. Good luck creators!

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