Tutorial: Building a Dashboard using Horizon

This tutorial covers how to use the various components in horizon to build an example dashboard and a panel with a tab which has a table containing data from the back end.

As an example, we’ll create a new My Dashboard dashboard with a My Panel panel that has an Instances Tab tab. The tab has a table which contains the data pulled by the Nova instances API.

Note

This tutorial assumes you have either a devstack or openstack environment up and running. There are a variety of other resources which may be helpful to read first. For example, you may want to start with the Horizon quickstart guide or the Django tutorial.

Creating a dashboard

The quick version

Horizon provides a custom management command to create a typical base dashboard structure for you. Run the following commands at the same location where the run_tests.sh file resides. It generates most of the boilerplate code you need:

mkdir openstack_dashboard/dashboards/mydashboard

./run_tests.sh -m startdash mydashboard \
              --target openstack_dashboard/dashboards/mydashboard

mkdir openstack_dashboard/dashboards/mydashboard/mypanel

./run_tests.sh -m startpanel mypanel \
               --dashboard=openstack_dashboard.dashboards.mydashboard \
               --target=openstack_dashboard/dashboards/mydashboard/mypanel

You will notice that the directory mydashboard gets automatically populated with the files related to a dashboard and the mypanel directory gets automatically populated with the files related to a panel.

Structure

If you use the tree mydashboard command to list the mydashboard directory in openstack_dashboard/dashboards , you will see a directory structure that looks like the following:

mydashboard
├── dashboard.py
├── dashboard.pyc
├── __init__.py
├── __init__.pyc
├── mypanel
│   ├── __init__.py
│   ├── panel.py
│   ├── templates
│   │   └── mypanel
│   │       └── index.html
│   ├── tests.py
│   ├── urls.py
│   └── views.py
├── static
│   └── mydashboard
│       ├── css
│       │   └── mydashboard.css
│       └── js
│           └── mydashboard.js
└── templates
    └── mydashboard
        └── base.html

For this tutorial, we will not deal with the static directory, or the tests.py file. Leave them as they are.

With the rest of the files and directories in place, we can move on to add our own dashboard.

Defining a dashboard

Open the dashboard.py file. You will notice the following code has been automatically generated:

from django.utils.translation import ugettext_lazy as _

import horizon


class Mydashboard(horizon.Dashboard):
   name = _("Mydashboard")
   slug = "mydashboard"
   panels = ()           # Add your panels here.
   default_panel = ''    # Specify the slug of the dashboard's default panel.


horizon.register(Mydashboard)

If you want the dashboard name to be something else, you can change the name attribute in the dashboard.py file . For example, you can change it to be My Dashboard

name = _("My Dashboard")

A dashboard class will usually contain a name attribute (the display name of the dashboard), a slug attribute (the internal name that could be referenced by other components), a list of panels, default panel, etc. We will cover how to add a panel in the next section.

Creating a panel

We’ll create a panel and call it My Panel.

Structure

As described above, the mypanel directory under openstack_dashboard/dashboards/mydashboard should look like the following:

mypanel
 ├── __init__.py
 ├── models.py
 ├── panel.py
 ├── templates
 │   └── mypanel
 │     └── index.html
 ├── tests.py
 ├── urls.py
 └── views.py

Defining a panel

The panel.py file referenced above has a special meaning. Within a dashboard, any module name listed in the panels attribute on the dashboard class will be auto-discovered by looking for the panel.py file in a corresponding directory (the details are a bit magical, but have been thoroughly vetted in Django’s admin codebase).

Open the panel.py file, you will have the following auto-generated code:

from django.utils.translation import ugettext_lazy as _

import horizon

from openstack_dashboard.dashboards.mydashboard import dashboard


class Mypanel(horizon.Panel):
    name = _("Mypanel")
    slug = "mypanel"


dashboard.Mydashboard.register(Mypanel)

If you want the panel name to be something else, you can change the name attribute in the panel.py file . For example, you can change it to be My Panel:

name = _("My Panel")

Open the dashboard.py file again, insert the following code above the Mydashboard class. This code defines the Mygroup class and adds a panel called mypanel:

class Mygroup(horizon.PanelGroup):
    slug = "mygroup"
    name = _("My Group")
    panels = ('mypanel',)

Modify the Mydashboard class to include Mygroup and add mypanel as the default panel:

class Mydashboard(horizon.Dashboard):
   name = _("My Dashboard")
   slug = "mydashboard"
   panels = (Mygroup,)  # Add your panels here.
   default_panel = 'mypanel'  # Specify the slug of the default panel.

The completed dashboard.py file should look like the following:

from django.utils.translation import ugettext_lazy as _

import horizon


class Mygroup(horizon.PanelGroup):
    slug = "mygroup"
    name = _("My Group")
    panels = ('mypanel',)


class Mydashboard(horizon.Dashboard):
    name = _("My Dashboard")
    slug = "mydashboard"
    panels = (Mygroup,)  # Add your panels here.
    default_panel = 'mypanel'  # Specify the slug of the default panel.


horizon.register(Mydashboard)

Tables, Tabs, and Views

We’ll start with the table, combine that with the tabs, and then build our view from the pieces.

Defining a table

Horizon provides a SelfHandlingForm DataTable class which simplifies the vast majority of displaying data to an end-user. We’re just going to skim the surface here, but it has a tremendous number of capabilities.

Create a tables.py file under the mypanel directory and add the following code:

from django.utils.translation import ugettext_lazy as _

from horizon import tables


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:
        name = "instances"
        verbose_name = _("Instances")

There are several things going on here... we created a table subclass, and defined four columns that we want to retrieve data and display. Each of those columns defines what attribute it accesses on the instance object as the first argument, and since we like to make everything translatable, we give each column a verbose_name that’s marked for translation.

Lastly, we added a Meta class which indicates the meta object that describes the instances table.

Note

This is a slight simplification from the reality of how the instance object is actually structured. In reality, accessing other attributes requires an additional step.

Adding actions to a table

Horizon provides three types of basic action classes which can be taken on a table’s data:

There are also additional actions which are extensions of the basic Action classes:

Now let’s create and add a filter action to the table. To do so, we will need to edit the tables.py file used above. To add a filter action which will only show rows which contain the string entered in the filter field, we must first define the action:

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

Note

The action specified above will default the filter_type to be "query". This means that the filter will use the client side table sorter.

Then, we add that action to the table actions for our table.:

class InstancesTable:
    class Meta:
        table_actions = (MyFilterAction,)

The completed tables.py file should look like the following:

from django.utils.translation import ugettext_lazy as _

from horizon import tables


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:
        name = "instances"
        verbose_name = _("Instances")
        table_actions = (MyFilterAction,)

Defining tabs

So we have a table, ready to receive our data. We could go straight to a view from here, but in this case we’re also going to use horizon’s TabGroup class.

Create a tabs.py file under the mypanel directory. Let’s make a tab group which has one tab. The completed code should look like the following:

from django.utils.translation import ugettext_lazy as _

from horizon import exceptions
from horizon import tabs

from openstack_dashboard import api
from openstack_dashboard.dashboards.mydashboard.mypanel import tables


class InstanceTab(tabs.TableTab):
    name = _("Instances Tab")
    slug = "instances_tab"
    table_classes = (tables.InstancesTable,)
    template_name = ("horizon/common/_detail_table.html")
    preload = False

    def has_more_data(self, table):
        return self._has_more

    def get_instances_data(self):
        try:
            marker = self.request.GET.get(
                        tables.InstancesTable._meta.pagination_param, None)

            instances, self._has_more = api.nova.server_list(
                self.request,
                search_opts={'marker': marker, 'paginate': True})

            return instances
        except Exception:
            self._has_more = False
            error_message = _('Unable to get instances')
            exceptions.handle(self.request, error_message)

            return []

class MypanelTabs(tabs.TabGroup):
    slug = "mypanel_tabs"
    tabs = (InstanceTab,)
    sticky = True

This tab gets a little more complicated. The tab handles data tables (and all their associated features), and it also uses the preload attribute to specify that this tab shouldn’t be loaded by default. It will instead be loaded via AJAX when someone clicks on it, saving us on API calls in the vast majority of cases.

Additionally, the displaying of the table is handled by a reusable template, horizon/common/_detail_table.html. Some simple pagination code was added to handle large instance lists.

Lastly, this code introduces the concept of error handling in horizon. The horizon.exceptions.handle() function is a centralized error handling mechanism that takes all the guess-work and inconsistency out of dealing with exceptions from the API. Use it everywhere.

Tying it together in a view

There are lots of pre-built class-based views in horizon. We try to provide the starting points for all the common combinations of components.

Open the views.py file, the auto-generated code is like the following:

from horizon import views


class IndexView(views.APIView):
    # 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

In this case we want a starting view type that works with both tabs and tables... that’d be the TabbedTableView class. It takes the best of the dynamic delayed-loading capabilities tab groups provide and mixes in the actions and AJAX-updating that tables are capable of with almost no work on the user’s end. Change views.APIView to be tabs.TabbedTableView and add MypanelTabs as the tab group class in the IndexView class:

class IndexView(tabs.TabbedTableView):
    tab_group_class = mydashboard_tabs.MypanelTabs

After importing the proper package, the completed views.py file now looks like the following:

from horizon import tabs

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


class IndexView(tabs.TabbedTableView):
    tab_group_class = mydashboard_tabs.MypanelTabs
    template_name = 'mydashboard/mypanel/index.html'

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

URLs

The auto-generated urls.py file is like:

from django.conf.urls import patterns
from django.conf.urls import url

from openstack_dashboard.dashboards.mydashboard.mypanel.views \
    import IndexView


urlpatterns = patterns(
    '',
    url(r'^$', IndexView.as_view(), name='index'),
)

Adjust the import of IndexView to make the code readable:

from openstack_dashboard.dashboards.mydashboard.mypanel import views

Replace the existing url pattern with the following line:

url(r'^$',
    views.IndexView.as_view(), name='index'),

The completed urls.py file should look like the following:

from django.conf.urls import patterns
from django.conf.urls import url

from openstack_dashboard.dashboards.mydashboard.mypanel import views


urlpatterns = patterns('',
    url(r'^$',
        views.IndexView.as_view(), name='index'),
)

The template

Open the index.html file in the mydashboard/mypanel/templates/mypanel directory, the auto-generated code is like the following:

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

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

{% block main %}
{% endblock %}

The main block must be modified to insert the following code:

<div class="row">
   <div class="col-sm-12">
   {{ tab_group.render }}
   </div>
</div>

If you want to change the title of the index.html file to be something else, you can change it. For example, change it to be My Panel in the block title section. If you want the title in the block page_header section to be something else, you can change it. For example, change it to be My Panel. The updated code could be like:

{% extends 'base.html' %}
{% load i18n %}
{% block title %}{% trans "My Panel" %}{% endblock %}

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

{% block main %}
<div class="row">
   <div class="col-sm-12">
   {{ tab_group.render }}
   </div>
</div>
{% endblock %}

This gives us a custom page title, a header, and renders our tab group provided by the view.

With all our code in place, the only thing left to do is to integrate it into our OpenStack Dashboard site.

Note

For more information about Django views, URLs and templates, please refer to the Django documentation.

Enable and show the dashboard

In order to make My Dashboard show up along with the existing dashboards like Project or Admin on horizon, you need to create a file called _50_mydashboard.py under openstack_dashboard/enabled and add the following:

# The name of the dashboard to be added to HORIZON['dashboards']. Required.
DASHBOARD = 'mydashboard'

# If set to True, this dashboard will not be added to the settings.
DISABLED = False

# A list of applications to be added to INSTALLED_APPS.
ADD_INSTALLED_APPS = [
    'openstack_dashboard.dashboards.mydashboard',
]

Run and check the dashboard

Everything is in place, now run Horizon on the different port:

./run_tests.sh --runserver 0.0.0.0:8877

Go to http://<your server>:8877 using a browser. After login as an admin you should be able see My Dashboard shows up at the left side on horizon. Click it, My Group will expand with My Panel. Click on My Panel, the right side panel will display an Instances Tab which has an Instances table.

If you don’t see any instance data, you haven’t created any instances yet. Go to dashboard Project -> Images, select a small image, for example, cirros-0.3.1-x86_64-uec , click Launch and enter an Instance Name, click the button Launch. It should create an instance if the OpenStack or devstack is correctly set up. Once the creation of an instance is successful, go to My Dashboard again to check the data.

Adding a complex action to a table

For a more detailed look into adding a table action, one that requires forms for gathering data, you can walk through Adding a complex action to a table tutorial.

Conclusion

What you’ve learned here is the fundamentals of how to write interfaces for your own project based on the components horizon provides.

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