Tutorial: Adding a complex action to a table¶

This tutorial covers how to add a more complex action to a table, one that requires an action and form definitions, as well as changes to the view, urls, and table.

This tutorial assumes you have already completed Tutorial: Building a Dashboard using Horizon. If not, please do so now as we will be modifying the files created there.

This action will create a snapshot of the instance. When the action is taken, it will display a form that will allow the user to enter a snapshot name, and will create that snapshot when the form is closed using the Create snapshot button.

Defining the view¶

To define the view, we must create a view class, along with the template (HTML) file and the form class for that view.

The template file¶

The template file contains the HTML that will be used to show the view.

Create a create_snapshot.html file under the mypanel/templates/mypanel directory and add the following code:

{% extends 'base.html' %}
{% load i18n %}
{% block title %}{% trans "Create Snapshot" %}{% endblock %}

{% block page_header %}
  {% include "horizon/common/_page_header.html" with title=_("Create a Snapshot") %}
{% endblock page_header %}

{% block main %}
    {% include 'mydashboard/mypanel/_create_snapshot.html' %}
{% endblock %}

As you can see, the main body will be defined in _create_snapshot.html, so we must also create that file under the mypanel/templates/mypanel directory. It should contain the following code:

{% extends "horizon/common/_modal_form.html" %}
{% load i18n %}

{% block modal-body-right %}
    <h3>{% trans "Description:" %}</h3>
    <p>{% trans "Snapshots preserve the disk state of a running instance." %}</p>
{% endblock %}

The form¶

Horizon provides a SelfHandlingForm class which simplifies some of the details involved in creating a form. Our form will derive from this class, adding a character field to allow the user to specify a name for the snapshot, and handling the successful closure of the form by calling the nova api to create the snapshot.

Create the forms.py file under the mypanel directory and add the following:

from django.urls import reverse
from django.utils.translation import gettext_lazy as _

from horizon import exceptions
from horizon import forms

from openstack_dashboard import api


class CreateSnapshot(forms.SelfHandlingForm):
    instance_id = forms.CharField(label=_("Instance ID"),
                                  widget=forms.HiddenInput(),
                                  required=False)
    name = forms.CharField(max_length=255, label=_("Snapshot Name"))

    def handle(self, request, data):
        try:
            snapshot = api.nova.snapshot_create(request,
                                                data['instance_id'],
                                                data['name'])
            return snapshot
        except Exception:
            exceptions.handle(request,
                              _('Unable to create snapshot.'))

The view¶

Now, the view will tie together the template and the form. Horizon provides a ModalFormView class which simplifies the creation of a view that will contain a modal form.

Open the views.py file under the mypanel directory and add the code for the CreateSnapshotView and the necessary imports. The complete file should now look something like this:

from django.urls import reverse
from django.urls import reverse_lazy
from django.utils.translation import gettext_lazy as _

from horizon import tabs
from horizon import exceptions
from horizon import forms

from horizon.utils import memoized

from openstack_dashboard import api

from openstack_dashboard.dashboards.mydashboard.mypanel \
    import forms as project_forms

from openstack_dashboard.dashboards.mydashboard.mypanel \
    import tabs as mydashboard_tabs


class IndexView(tabs.TabbedTableView):
    tab_group_class = mydashboard_tabs.MypanelTabs
    # A very simple class-based view...
    template_name = 'mydashboard/mypanel/index.html'

    def get_data(self, request, context, *args, **kwargs):
        # Add data to the context here...
        return context


class CreateSnapshotView(forms.ModalFormView):
    form_class = project_forms.CreateSnapshot
    template_name = 'mydashboard/mypanel/create_snapshot.html'
    success_url = reverse_lazy("horizon:project:images:index")
    modal_id = "create_snapshot_modal"
    modal_header = _("Create Snapshot")
    submit_label = _("Create Snapshot")
    submit_url = "horizon:mydashboard:mypanel:create_snapshot"

    @memoized.memoized_method
    def get_object(self):
        try:
            return api.nova.server_get(self.request,
                                       self.kwargs["instance_id"])
        except Exception:
            exceptions.handle(self.request,
                              _("Unable to retrieve instance."))

    def get_initial(self):
        return {"instance_id": self.kwargs["instance_id"]}

    def get_context_data(self, **kwargs):
        context = super(CreateSnapshotView, self).get_context_data(**kwargs)
        instance_id = self.kwargs['instance_id']
        context['instance_id'] = instance_id
        context['instance'] = self.get_object()
        context['submit_url'] = reverse(self.submit_url, args=[instance_id])
        return context

Adding the url¶

We must add the url for our new view. Open the urls.py file under the mypanel directory and add the following as a new url pattern:

url(r'^(?P<instance_id>[^/]+)/create_snapshot/$',
    views.CreateSnapshotView.as_view(),
    name='create_snapshot'),

The complete urls.py file should look like this:

from django.urls import re_path

from openstack_dashboard.dashboards.mydashboard.mypanel import views


urlpatterns = [
    re_path(r'^$',
            views.IndexView.as_view(), name='index'),
    re_path(r'^(?P<instance_id>[^/]+)/create_snapshot/$',
            views.CreateSnapshotView.as_view(),
            name='create_snapshot'),
]

Define the action¶

Horizon provides a LinkAction class which simplifies adding an action which can be used to display another view.

We will add a link action to the table that will be accessible from each row in the table. The action will use the view defined above to create a snapshot of the instance represented by the row in the table.

To do this, we must edit the tables.py file under the mypanel directory and add the following:

def is_deleting(instance):
    task_state = getattr(instance, "OS-EXT-STS:task_state", None)
    if not task_state:
        return False
    return task_state.lower() == "deleting"


class CreateSnapshotAction(tables.LinkAction):
    name = "snapshot"
    verbose_name = _("Create Snapshot")
    url = "horizon:mydashboard:mypanel:create_snapshot"
    classes = ("ajax-modal",)
    icon = "camera"

    # This action should be disabled if the instance
    # is not active, or the instance is being deleted
    def allowed(self, request, instance=None):
        return instance.status in ("ACTIVE") \
            and not is_deleting(instance)

We must also add our new action as a row action for the table:

row_actions = (CreateSnapshotAction,)

The complete tables.py file should look like this:

from django.utils.translation import gettext_lazy as _

from horizon import tables


def is_deleting(instance):
    task_state = getattr(instance, "OS-EXT-STS:task_state", None)
    if not task_state:
        return False
    return task_state.lower() == "deleting"


class CreateSnapshotAction(tables.LinkAction):
    name = "snapshot"
    verbose_name = _("Create Snapshot")
    url = "horizon:mydashboard:mypanel:create_snapshot"
    classes = ("ajax-modal",)
    icon = "camera"

    def allowed(self, request, instance=None):
        return instance.status in ("ACTIVE") \
            and not is_deleting(instance)


class MyFilterAction(tables.FilterAction):
    name = "myfilter"


class InstancesTable(tables.DataTable):
    name = tables.Column("name", verbose_name=_("Name"))
    status = tables.Column("status", verbose_name=_("Status"))
    zone = tables.Column('availability_zone', verbose_name=_("Availability Zone"))
    image_name = tables.Column('image_name', verbose_name=_("Image Name"))

    class Meta(object):
        name = "instances"
        verbose_name = _("Instances")
        table_actions = (MyFilterAction,)
        row_actions = (CreateSnapshotAction,)

Run and check the dashboard¶

We must once again run horizon to verify our dashboard is working:

$ tox -e runserver -- 0:9000

Go to http://<your server>:9000 using a browser. After login as an admin, display My Panel to see the Instances table. For every ACTIVE instance in the table, there will be a Create Snapshot action on the row. Click on Create Snapshot, enter a snapshot name in the form that is shown, then click to close the form. The Project Images view should be shown with the new snapshot added to the table.

Conclusion¶

What you’ve learned here is the fundamentals of how to add a table action that requires a form for data entry. This can easily be expanded from creating a snapshot to other API calls that require more complex forms to gather the necessary information.

If you have feedback on how this tutorial could be improved, please feel free to submit a bug against launchpad:horizon.

Tutorial: Adding a complex action to a table