Synnefo » ./kamaki

Creating applications with kamaki API

=====================================

Kamaki features a clients API for building third-party client applications that

communicate with OpenStack and / or Synnefo cloud services. The package is

called *kamaki.clients* and serves as a lib.

A showcase of an application built on *kamaki.clients* is *kamaki.cli*, the

command line interface of kamaki.

Since Synnefo services are build as OpenStack extensions, an inheritance

approach has been chosen for implementing clients for both. In specific,

the *compute*, *storage* and *image* modules are client implementations for the

OpenStack compute and OpenStack object-store APIs, respectively. The rest of the

modules implement the Synnefo extensions (i.e., *cyclades* and 

*cyclades_rest_api* extents *compute*, *pithos* and *pithos_rest_api* extent

*storage*) or novel Synnefo services (*image* for *plankton*).

Setup a client instance

-----------------------

There is a client for every API, therefore an external applications should

instantiate they kamaki clients they need. For example, to manage virtual

servers and stored objects / files, an application would probably need to

instantiate the CycladesClient and PithosClient respectively.

.. code-block:: python

    :emphasize-lines: 1

    Example 1.1: Instantiate Cyclades and Pithos clients

    from kamaki.clients.cyclades import CycladesClient

    from kamaki.clients.pithos import PithosClient

    my_cyclades_client = CycladesClient(base_url, token)

    my_pithos_client = PithosClient(base_url, token, account, container)

.. note:: *cyclades* and *pithos* clients inherit ComputeClient from *compute*

    and StorageClient from *storage*, respectively. Separate ComputeClient or

    StorageClient objects should be used only when implementing applications for

    strict OpenStack Compute or Storage services.

Using endpoints to get the base_url

-----------------------------------

In OpenStack, each service (e.g., `compute`, `object-store`, etc.) has a number

of `endpoints`. These `endpoints` are actually URIs that are used by kamaki as

prefixes to form the corresponding API calls. Client applications need just

one of these these `endpoints`, namely the `publicURL`, which is also referred

to as `base_url` in kamaki client libraries.

Here are instructions for getting the base_url for a service::

    1. From the deployment UI get the AUTHENTICATION_URL and TOKEN

        (Example 1.2)

    2. Use them to instantiate an AstakosClient

        (Example 1.2)

    3. Use AstakosClient instance to get the endpoints of the service of interest

        (Example 1.3)

    4. The 'publicURL' endpoint is the base_url we are looking for

        (Example 1.3)

The AstakosClient is a client for the Synnefo/Astakos server. Synnefo/Astakos

is an identity server that implements the OpenStack identity API. Therefore, it

can be used to get the `base_url` values needed for initializing kamaki clients.

Kamaki simplifies this process with the astakos client library.

Let's review the process with examples.

First, an astakos client must be initialized (Example 1.2). An

AUTHENTICATION_URL and a TOKEN can be acquired from the Synnefo deployment UI.

.. code-block:: python

    :emphasize-lines: 1

    Example 1.2: Initialize an astakos client

    from kamaki.clients.astakos import AstakosClient

    my_astakos_client = AstakosClient(AUTHENTICATION_URL, TOKEN)

Next, the astakos client can be used to retrieve the base_url values for the

servers of interest. In this case (Example 1.3) they are *cyclades*

and *pithos*. A number of endpoints is assigned to each service, but kamaki

clients only need the one labeled as ``publicURL``.

.. code-block:: python

    :emphasize-lines: 1

    Example 1.3: Retrieve cyclades and pithos base_url values

    cyclades_endpoints = my_astakos_client.get_service_endpoints('compute')

    cyclades_base_url = cyclades_endpoints['publicURL']

    pithos_endpoints = my_astakos_client.get_service_endpoints('object-store')

    pithos_base_url = pithos_endpoints['publicURL']

The ``get_service_endpoints`` method is called with the service name as an

argument. Here are the service names for the kamaki clients::

    storage.StorageClient, pithos.PithosClient      -->     object-store

    compute.ComputeClient, cyclades.CycladesClient  -->     compute

    image.ImageClient                               -->     image

    astakos.AstakosClient                           -->     identity, account

Use client methods

------------------

At this point we assume that we can initialize a client, so the initialization

step will be omitted in most of the examples that follow.

The next step is to take a look at the member methods of each particular client.

A detailed catalog of the member methods for all client classes can be found at

:ref:`the-client-api-ref`

In the following example, the *cyclades* and *pithos* clients of example 1.1

are used to extract some information through the remote service APIs. The information is then printed to the standard output.

.. code-block:: python

    :emphasize-lines: 1,2

    Example 1.4: Print server name and OS for server with server_id

                Print objects in container mycont

    srv = my_cyclades_client.get_server_info(server_id)

    print("Server Name: %s (with OS %s" % (srv['name'], srv['os']))

    obj_list = my_pithos_client.list_objects(mycont)

    for obj in obj_list:

        print('  %s of %s bytes' % (obj['name'], obj['bytes']))

.. code-block:: console

    :emphasize-lines: 1

    * A run of examples 1.1 + 1.4 *

    $ python test_script.py

    Server Name: A Debian Server (with OS Debian Base)

      lala.txt of 34 bytes

      test.txt of 1232 bytes

      testDir/ of 0 bytes

    $ 

Error handling

--------------

The *kamaki.clients* error class is ClientError. A ClientError is raised for

any kind of *kamaki.clients* errors (errors reported by servers, type errors in

arguments, etc.).

A ClientError contains::

    message     The error message.

    status      An optional error code, e.g., after a server error.

    details     Optional list of messages with error details.

The following example concatenates examples 1.1 to 1.4 plus error handling

.. code-block:: python

    Example 1.5: Error handling

    from kamaki.clients import ClientError

    from kamaki.clients.astakos import AstakosClient

    from kamaki.clients.cyclades import CycladesClient

    from kamaki.clients.pithos import PithosClient

    try:

        my_astakos_client = AstakosClient(AUTHENTICATION_URL, TOKEN)

        my_astakos_client.authenticate()

    except ClientError:

        print('Failed to authenticate user token')

        return 1

    try:

        cyclades_endpoints = my_astakos_client.get_service_endpoints('compute')

        cyclades_base_url = cyclades_endpoints['publicURL']

    except ClientError:

        print('Failed to get endpoints for cyclades')

    try:

        my_cyclades_client = CycladesClient(cyclades_base_url, token)

    except ClientError:

        print('Failed to initialize Cyclades client')

    try:

        pithos_endpoints = my_astakos_client.get_service_endpoints('object-store')

        pithos_base_url = pithos_endpoints['publicURL']

    except ClientError:

        print('Failed to get endpoints for pithos')

    try:

        my_pithos_client = PithosClient(pithos_base_url, token, account, container)

    except ClientError:

        print('Failed to initialize Pithos+ client')

    try:

        srv = my_cyclades_client.get_server_info(server_id)

        print("Server Name: %s (with OS %s" % (srv['name'], srv['os']))

        obj_list = my_pithos_client.list_objects(mycont)

        for obj in obj_list:

            print('  %s of %s bytes' % (obj['name'], obj['bytes']))

    except ClientError as e:

        print('Error: %s' % e)

        if e.status:

            print('- error code: %s' % e.status)

        if e.details:

            for detail in e.details:

                print('- %s' % detail)

Scripts

-------

Batch-create servers

''''''''''''''''''''

.. code-block:: python

    #! /usr/bin/python

    from kamaki.clients.astakos import AstakosClient

    from kamaki.clients.cyclades import CycladesClient

    AUTHENTICATION_URL = 'https://accounts.example.com/identity/v2.0'

    TOKEN = 'replace this with your token'

    user = AstakosClient(AUTHENTICATION_URL, TOKEN)

    cyclades_endpoints = user.get_service_endpoints('compute')

    CYCLADES_URL = cyclades_endpoints['publicURL']

    cyclades = CycladesClient(CYCLADES_URL, TOKEN)

    #  (name, flavor-id, image-id)

    servers = [

        ('My Debian Server', 1, 'my-debian-base-image-id'),

        ('My Windows Server', 3, 'my-windows-8-image-id'),

        ('My Ubuntu Server', 3, 'my-ubuntu-12-image-id'),

    ]

    for name, flavor_id, image_id in servers:

        cyclades.create_server(name, flavor_id, image_id)

Batch-create 4 servers of the same kind

'''''''''''''''''''''''''''''''''''''''

.. code-block:: python

    #! /usr/bin/python

    from kamaki.clients.astakos import AstakosClient

    from kamaki.clients.cyclades import CycladesClient

    AUTHENTICATION_URL = 'https://accounts.example.com/identity/v2.0'

    TOKEN = 'replace this with your token'

    user = AstakosClient(AUTHENTICATION_URL, TOKEN)

    cyclades_endpoints = user.get_service_endpoints('compute')

    CYCLADES_URL = cyclades_endpoints['publicURL']

    cyclades = CycladesClient(CYCLADES_URL, TOKEN)

    for i in range(4):

        name, flavor_id, image_id = 'Server %s' % (i + 1), 3, 'some-image-id'

        cyclades.create_server(name, flavor_id, image_id)

Register a banch of pre-uploaded images

'''''''''''''''''''''''''''''''''''''''

.. code-block:: python

    #! /usr/bin/python

    from kamaki.clients import ClientError

    from kamaki.clients.astakos import AstakosClient

    from kamaki.clients.pithos import PithosClient

    from kamaki.clients.image import ImageClient

    AUTHENTICATION_URL = 'https://accounts.example.com/identity/v2.0'

    TOKEN = 'replace this with your token'

    IMAGE_CONTAINER = 'images'

    astakos = AstakosClient(AUTHENTICATION_URL, TOKEN)

    USER_UUID = astakos.user_term('uuid')

    PITHOS_URL = astakos.get_service_endpoints('object-store')['publicURL']

    pithos = PithosClient(PITHOS_URL, TOKEN, USER_UUID, IMAGE_CONTAINER)

    IMAGE_URL = astakos.get_service_endpoints('image')['publicURL']

    plankton = ImageClient(IMAGE_URL, TOKEN)

    for img in pithos.list_objects():

        IMAGE_PATH = img['name']

        try:

            r = plankton.register(

                name='Image %s' % img,

                location=(USER_UUID, IMAGE_CONTAINER, IMAGE_PATH))

            print 'Image %s registered with id %s' % (r['name'], r['id'])

        except ClientError:

            print 'Failed to register image %s' % IMAGE_PATH

Two servers and a private network

'''''''''''''''''''''''''''''''''

.. code-block:: python

    #! /user/bin/python

    from kamaki.clients.astakos import AstakosClient

    from kamaki.clients.cyclades import CycladesClient

    AUTHENTICATION_URL = 'https://accounts.example.com/identity/v2.0'

    TOKEN = 'replace this with your token'

    astakos = AstakosClient(AUTHENTICATION_URL, TOKEN)

    cyclades_endpoints = user.get_service_endpoints('compute')

    CYCLADES_URL = cyclades_endpoints['publicURL']

    FLAVOR_ID = 'put your flavor id here'

    IMAGE_ID = 'put your image id here'

    cyclades = CycladesClient(CYCLADES_URL, TOKEN)

    srv1 = cyclades.create_server('server 1', FLAVOR_ID, IMAGE_ID)

    srv2 = cyclades.create_server('server 2', FLAVOR_ID, IMAGE_ID)

    srv_state1 = cyclades.wait_server(srv1['id'])

    assert srv_state1 in ('ACTIVE'), 'Server 1 built failure'

    srv_state2 = cyclades.wait_server(srv2['id'])

    assert srv_state2 in ('ACTIVE'), 'Server 2 built failure'

    net = cyclades.create_network('My private network')

    net_state = cyclades.wait_network(net['id'])

    assert net_state in ('ACTIVE', ), 'Network built failure'

    cyclades.connect_server(srv1['id'], net['id'])

    cyclades.connect_server(srv2['id'], net['id'])