Table of Contents
Features are very useful for building Drupal profiles (re-usable applications). They provide a way to capture and save in code the customizations that are done to a Drupal site/application. I will describe how I use them in B-Translator.
1 Benefits of using features
Some of the main benefits of using features are these:
- They help the development and maintenance of the application. Customization/configuration changes can be tracked and versioned (for example in git) just like the code of the application.
- They help the installation of a new instance of the application. Customizations can be replayed (applied) easily on a new installation of the application, without having to repeat them manually.
- They make the application structured (as opposed to monolithic). For example drupalchat is offered as a feature and can be installed very easily by installing the feature. But sites that do not want to use it just don't install that feature.
For more details about features (and their features) you can read these blogs:
2 Creating features
Features can be created and managed through UI. However I find the UI for creating features not suitable (tedious, sluggish, unreliable), at least when creating features for a Drupal profile. Fortunately they can also be fully managed from the command line (with drush):
drush help --filter=features
First of all, we can get a list of all the so called features components:
drush @dev help features-components drush @dev features-components '%:%' > features-components.txt
These are all the possible chunks of configuration that can be saved in a feature. All we have to do is to search and select the ones that are relevant for the feature that we want to build and then create a feature with these components. This will automatically generate the code (Drupal API) that is necessary to apply these configurations.
For example, these are the components that I have selected for the layout feature (which is supposed to re-construct automatically the layout and look of a freshly installed B-Translator site):
variable:theme_bootstrap1_settings variable:theme_default box:headerbox context:admin context:content context:frontpage context:page context:sitewide context:translations views_view:front_page variable:site_frontpage menu_links:main-menu:<front> menu_links:main-menu:node/9 menu_links:main-menu:translations menu_links:main-menu:node/1 menu_links:main-menu:contact menu_custom:navig-menu menu_links:navig-menu:translations menu_links:navig-menu:node/9 menu_links:navig-menu:translations/search menu_links:navig-menu:node/1 menu_links:navig-menu:contact
These include the theme, blocks layout, the front page view, and the menus.
Now I can create a feature that includes these components with a command like this:
drush @dev features-export \ --destination=profiles/btranslator/modules/features \ btranslator_layout $(cat layout_components)
It creates a feature on the directory:
Other features that I have created are: btranslator_disqus,
btranslator_mass_contact, btranslator_googleanalytics, etc. In
order to recreate them easily, the script
be used. It will create a feature for each list of components that
is on the directory
create-features.sh has a content like this:
3 Customizing features manually
A feature is basically just a Drupal module (although it is
generated automatically by the command
features-export). So, we
can further customize it manually if needed. And sometimes there is
the need for manual customization because the automatic generation
cannot get always everything right. In the case of the layout
feature I added the file
btranslator_layout.install, which uses
hook_enable() to make further customizations after the feature is
It creates aliases, which cannot be handled properly by the features. It creates a Login menu link, which is not handled propperly by the features (although in general menu links can be handled quite well by the features). It also sets the correct settings for the blocks in a simple way, although there are other ways to handle them by the features.
4 Making features configurable
Some of the features are required and will be automatically installed when the (btranslator) profile is installed, and some others are optional and can be installed later by the site administrator, if they wish. Most of these features are closely related to some contrib modules and basically just save default/reasonable values for the configuration settings of the module.
Some of these modules are just wrappers to external API services, like disqus, sharethis, janrain, recaptcha, googleanalytics, etc. Usually they need some API keys or any other private attributes that are different from site to site. We cannot save these private attributes on the feature, because they are specific for each different site. But we would like to offer the administrator/maintainer of the (B-Translator) application an easy way to manage them, without having to search up and down among a huge number of configuration options available to the Drupal admin. In order to do this, I have customized the automatically generated features, taking advantage of the fact that they are just Drupal modules, and anything that works for Drupal modules works for them too.
For example, for the feature btranslator_googleanalytics, I have
added this line on
I have also created the file
with a content like this:
It creates a configuration page for GoogleAnalytics under the
section of B-Translator configurations. This admin/config page
allows the site administrator to set quickly and easily the account
ID of GoogleAnalytics. All this is just normal Drupal stuff, which
can be done for any Drupal module. Nothing specially related to
features. For my convenience, I have copied the definition
of the form field from the googleanalytics Drupal module itself
(from the file
5 Saving and restoring private variables
If we cannot and should not keep private settings/attributes in
features, then there should be some other easy way for the site
administrators to backup and restore them, without making them
public and available to everyone. This can be done by the script
save-private-vars.sh. It takes a list of variables from
private-vars.txt and creates the file
which keeps the values of these variables and can restore them. It
works like this:
features/save-private-vars.sh @dev drush @dev php-script restore-private-vars.php
private-vars.txt looks like this:
disqus_domain disqus_userapikey disqus_publickey disqus_secretkey sharethis_publisherID sharethis_twitter_handle sharethis_twitter_suffix rpx_apikey simplenews_from_address simplenews_test_address mass_contact_default_sender_email mass_contact_default_sender_name recaptcha_private_key recaptcha_public_key googleanalytics_account
save-private-vars.sh has a content like this:
It can be useful as well to keep different sets of private variables for the live, test and dev sites.