Using the API

In this document we will see some examples on how to use the vPoller API.

You can use these examples for connecting your project to vPoller and send task requests for processing.

Sending task requests for processing

Connecting your Python project to vPoller is easy.

If you only need to be able to talk to vPoller and send task requests then using the VPollerClient class is the way to go.

The VPollerClient sends task requests to the vPoller Proxy, which distributes the task requests to the vPoller Workers.

Here is how you can send task requests from your Python project to vPoller for processing.

>>> from vpoller.client import VPollerClient
>>> msg = {'method': 'vm.discover', 'hostname': 'vc01.example.org'}
>>> client = VPollerClient(endpoint='tcp://localhost:10123')
>>> result = client.run(msg)
>>> print result

The above example code will send a task request for discovering all Virtual Machine managed objects from the vc01.example.org vSphere host.

And here is what the above example code does:

1. Imports the VPollerClient class from the vpoller.client module
2. Creates a message that will be sent to the vPoller Proxy endpoint. The message contains information such as the method to be processed, the vSphere hostname, and any additional details required for processing the task request.
3. We instantiate a VPollerClient object and set the endpoint to which the client will connect and send the task request for processing.
4. Using the run() method of a VPollerClient instance we send the task request over the wire and wait for response.

The VPollerClient class comes with builtin mechanism for automatic retry if it doesn’t receive a response after some period of time.

In order to control the retry and timeout settings of a VPollerClient object you can instantiate a client object this way:

>>> client = VPollerClient(
...     endpoint='tcp://localhost:10123',
...     retries=1,
...     timeout=1000
... )

Note, that the timeout argument used above is in milliseconds.

Here is another example which would get the runtime.powerState property for a specific Virtual Machine:

>>> import json
>>> from vpoller.client import VPollerClient
>>> msg = {
...     'method': 'vm.get',
...     'hostname': 'vc01.example.org',
...     'name': 'vm01.example.org',
...     'properties': ['name', 'runtime.powerState']
... }
>>> client = VPollerClient(endpoint='tcp://localhost:10123')
>>> result = client.run(msg)
>>> print json.dumps(result, indent=4)
{
    "msg": "Successfully retrieved object properties",
    "result": [
        {
             "runtime.powerState": "poweredOn",
             "name": "vm01.example.org"
        }
    ],
    "success": 0
}

As you can see we have successfully retrieved the runtime.powerState property for our Virtual Machine, which shows that our Virtual Machine is powered on.

For a full list of supported vPoller methods which you can use, please refer to the Supported methods by vPoller documentation.

You are also advised to check the vpoller.agent module, which is pretty well documented and provides information about each vPoller method and the expected message request in order to begin processing the task.

Executing vPoller tasks locally

Using the VPollerClient class as we’ve seen in the previous section of this document sends task requests to the vPoller Proxy, which distributes the tasks to any connected vPoller Worker.

This was a remote operation, where a client simply sends a task request and waits for a response.

You could also use vPoller in order to execute tasks locally, which means that no task is send over the wire and all the hard work is done on the local system.

Here is an example of interfacing with the vSphere Agents, which provides us with an interface to execute vPoller tasks locally.

The example below is equivalent to the examples in the previous section, except for one thing - it will be executed locally on the system running this code, and it will not be processed by a remote worker.

>>> from vpoller.agent import VSphereAgent
>>> agent = VSphereAgent(
...     user='root',
...     pwd='p4ssw0rd',
...     host='vc01.example.org'
... )
>>> agent.connect()
>>> result = agent.vm_discover(msg={})
>>> print result

Interfacing with vPoller from other languages

Connecting to vPoller from other languages is easy as well.

vPoller uses the ZeroMQ messaging library as the communication layer, so in theory every language that comes with ZeroMQ bindings should be able to interface with vPoller.

You can find below a simple example of using Ruby for sending a task request to vPoller:

/usr/bin/ruby

require 'json'
require 'rubygems'
require 'ffi-rzmq'

# Message we send to vPoller
msg = {:method => "vm.discover", :hostname => "vc01.example.org"}

# Create the ZeroMQ context and socket
context = ZMQ::Context.new(1)
socket = context.socket(ZMQ::REQ)

puts "Connecting to vPoller ..."
socket.connect("tcp://localhost:10123")

puts "Sending task request to vPoller ..."
socket.send_string(msg.to_json)

result = ''
socket.recv_string(result)

puts "Received reply from vPoller: #{result}"

You might also want to check the vpoller.client module for example code that you can use in order to implement a VPollerClient class in your language of choice.