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OpenStack Study: agents.py

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# Copyright 2012 IBM Corp.

#

# Licensed under the Apache License, Version 2.0 (the "License"); you may

# not use this file except in compliance with the License. You may obtain

# a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

# License for the specific language governing permissions and limitations

# under the License.

import webob.exc

from nova.api.openstack.compute.schemas.v3 import agents as schema

from nova.api.openstack import extensions

from nova.api.openstack import wsgi

from nova.api import validation

from nova import db

from nova import exception

ALIAS = "os-agents"

authorize = extensions.extension_authorizer('compute', 'v3:' + ALIAS)

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class AgentController(object):

"""The agent is talking about guest agent.The host can use this for

things like accessing files on the disk, configuring networking,

or running other applications/scripts in the guest while it is

running. Typically this uses some hypervisor-specific transport

to avoid being dependent on a working network configuration.

Xen, VMware, and VirtualBox have guest agents,although the Xen

driver is the only one with an implementation for managing them

in openstack. KVM doesn't really have a concept of a guest agent

(although one could be written).

You can find the design of agent update in this link:

http://wiki.openstack.org/AgentUpdate

and find the code in nova.virt.xenapi.vmops.VMOps._boot_new_instance.

In this design We need update agent in guest from host, so we need

some interfaces to update the agent info in host.

You can find more information about the design of the GuestAgent in

the following link:

http://wiki.openstack.org/GuestAgent

http://wiki.openstack.org/GuestAgentXenStoreCommunication

"""

@extensions.expected_errors(())

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    def index(self, req):

        """Return a list of all agent builds. Filter by hypervisor."""

        context = req.environ['nova.context']

        authorize(context)

        hypervisor = None

        agents = []

        if 'hypervisor' in req.GET:

            hypervisor = req.GET['hypervisor']

        for agent_build in db.agent_build_get_all(context, hypervisor):

            agents.append({'hypervisor': agent_build.hypervisor,

                           'os': agent_build.os,

                           'architecture': agent_build.architecture,

                           'version': agent_build.version,

                           'md5hash': agent_build.md5hash,

                           'agent_id': agent_build.id,

                           'url': agent_build.url})

        return {'agents': agents}

    @extensions.expected_errors((400, 404))

    @validation.schema(schema.update)

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    def update(self, req, id, body):

        """Update an existing agent build."""

        context = req.environ['nova.context']

        authorize(context)

        para = body['agent']

        url = para['url']

        md5hash = para['md5hash']

        version = para['version']

        try:

            db.agent_build_update(context, id,

                                {'version': version,

                                 'url': url,

                                 'md5hash': md5hash})

        except exception.AgentBuildNotFound as ex:

            raise webob.exc.HTTPNotFound(explanation=ex.format_message())

        return {"agent": {'agent_id': id, 'version': version,

                'url': url, 'md5hash': md5hash}}

    @extensions.expected_errors(404)

    @wsgi.response(204)

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    def delete(self, req, id):

        """Deletes an existing agent build."""

        context = req.environ['nova.context']

        authorize(context)

        try:

            db.agent_build_destroy(context, id)

        except exception.AgentBuildNotFound as ex:

            raise webob.exc.HTTPNotFound(explanation=ex.format_message())

    @extensions.expected_errors((400, 409))

    @wsgi.response(201)

    @validation.schema(schema.create)

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    def create(self, req, body):

        """Creates a new agent build."""

        context = req.environ['nova.context']

        authorize(context)

        agent = body['agent']

        hypervisor = agent['hypervisor']

        os = agent['os']

        architecture = agent['architecture']

        version = agent['version']

        url = agent['url']

        md5hash = agent['md5hash']

        try:

            agent_build_ref = db.agent_build_create(context,

                                                {'hypervisor': hypervisor,

                                                 'os': os,

                                                 'architecture': architecture,

                                                 'version': version,

                                                 'url': url,

                                                 'md5hash': md5hash})

            agent['agent_id'] = agent_build_ref.id

        except exception.AgentBuildExists as ex:

            raise webob.exc.HTTPConflict(explanation=ex.format_message())

        return {'agent': agent}

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class Agents(extensions.V3APIExtensionBase):

"""Agents support."""

name = "Agents"

alias = ALIAS

version = 1

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    def get_resources(self):

        resource = [extensions.ResourceExtension(ALIAS,

                                                AgentController())]

        return resource

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    def get_controller_extensions(self):

        """It's an abstract function V3APIExtensionBase and the extension

        will not be loaded without it.

        """

        return []