Spinning Code

One of the best practices for Drupal 8 that is still emerging is how to create modules with complex deployable configuration. In the past we often abused the features module to do this, and while that continues to be an option, with Drupal 8’s vastly improved configuration management options and the ability to install configuration easily I have been looking for something better. I particularly want to build modules that don’t have unnecessary dependencies but I can still reliably include all the needed configuration in my project. And after a few tries I think I’ve struck on an effective process.

Let’s start with a quick refresher on installing configuration for a Drupal 8 module. During module installation Drupal will load any yaml files that match configuration patterns it already knows about that are included in your module’s config/install directory. In theory this is great but if you want to include configuration that comes with other modules you have to figure out what files are needed; if you want to include configuration from core modules you probably will need to find a fairly large collection files to get all the required elements. Finding all those files, and copying them quickly and easily is the challenge I set out to solve.

My process starts with a local development sandbox site that is just there to support this development work, and I create a local git repository for the site’s configuration (I don’t need to connect it to a remote, like Bitbucket or GitHub, or handle all of the site’s code since it’s just to support finding changes to config files). Once installation and any base configuration is complete I export the site’s config to the directory covered by the repo (here I used d8_builder/config/sync, the site itself was at d8_builder/pub), and make sure all changes in the repository are committed:

Now I create my module and a second repository just for it. The module’s repository is linked to a remote since this is the actual product I’m creating.

With that plumbing in place I can to make whatever configuration change I need included in the module. Lately I’ve been creating a custom moderation workflow with several user roles and edge cases that will need to be deployed on a dozen or so sites, so you’ll see that reflected below, but this process should work for just about any project with lots of interrelated configuration.

Once I have completed a set of changes, I export the site’s configuration again making sure to avoid uuids and hashes that will cause trouble on import:  drupal config:export --remove-uuid --remove-config-hash

Now git can easily show which configuration files were changed, added, or removed:

Next I use git, xargs, and cp to copy those files into your module (hat tip on this detail to Andy Gregorowicz):
git ls-files -om --exclude-standard --exclude=core.extensions.yml |  xargs -I{} cp "{}" pub/modules/custom/fancy_workflow/config/install/

Notice that I skip the core.extensions.yml file. If your module had dependencies you’ll still need to update your module’s info.yml file to list them.

Now a quick commit and push of the changes to the module’s repo, and I’m ready to pull the module into other projects. I also commit the builder repo to ensure it’s easy to track any future changes.

This isn’t a replacement for tools like Configuration Installer, which are designed to handle an entire site, this is intended just for module development.

If you think you have a better solution, or that I’m missing something important please let me know.

I recently completed a Drupal 8 project that required pulling data from a remote database.  The actual data is not terribly complicated, so Drupal’s role in this case is mostly to provide an abstraction layer that converts the database into a (cacheable) JSON response. Pulling all the pieces together took a little more research and guessing than I expected so I figured I might save a few people time by writing it up. This is more of an intermediate than a beginner project and so I’m going to skip over lots of detail that important to making it all really work. To really understand what’s happening here you’ll want a basic understanding of Drupal 8’s controllers and database services.

What we’re doing here is creating a database service and a controller to provide a JSON endpoint. We’ll define the database connection, the Drupal service, and then the controller.

Drupal allows us to define database connections in the main settings file. This allows easy access to Drupal’s database services and query classes.

Connection Definition

The first step is to define the database connection in settings.php:

<?php
$databases['remote']['default'] = [
  'database' => 'extra_data',
  'username' => 'accessingUser',
  'password' => 'UseGoodPasswordsIn2017&Beyond',
  'prefix' => '',
  'host' => '10.10.1.1',
  'port' => '',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
  // I'll explain this detail later.
  'pdo' => [
    \PDO::ATTR_TIMEOUT => 5,
  ],
];

Services

Next we need to create a new database service using the new connection information. Drupal core’s database service can be leveraged to connect to additional databases by just defining your new connection as a service in your module’s services.yml file.

services:
  mydataservice.database:
    class: Drupal\Core\Database\Connection
    factory: 'Drupal\Core\Database\Database::getConnection'
    arguments: ['default', 'remote']

Notice the arguments from the database service are the array keys (in reverse order) from the settings.php definition of the connection.

That’s all it takes to create a new service that wraps around your database.

The Controller

That service is all well and good as far as it goes, but if we want to actually to send the data to the browser we need a controller to leverage our new service and send the response.

Using dependency injection I attached the service to the controller and it looked like it worked great.

<?php
  /**
 * Constructs a new DataSearchController object.
 */
public function __construct(ConfigFactory $config_factory, Connection $dataservice) {
  $this->config = $config_factory->get('mydataservice.datasettings');
  $this->database = $dataservice;
}

/**
 * {@inheritdoc}
 */
public static function create(ContainerInterface $container) {
  return new static(
    $container->get('mydataservice.database')
  );
}

public function getData(Request $request) {
  $query = $this->database->select('mytable', 'mt');
  // From here you gather your data and send your response...
}

In fact it did work flawlessly all the way through initial testing. Using the database service to get the data and the cacheable JSON response technique I’d worked out previously everything came together quickly. You could make a request of the controller with your search terms and the browser gets back a list of objects for display.

Then just before launch the client physically relocated the database server and didn’t tell us it would be offline. Turns out we hadn’t tested what happens to an injected database service when there is no response from the remote database server. The request would wait for the database connection to time out and then throw an exception that didn’t get handled in my code at all. There was no place to add a nice error message and it was incredibly slow since the timeout was 30 seconds.

So at the last minute I had two more problems to solve: trap the error and shorten the timeout on PDO connections.

Drupal 8 database services attempt their connection when the service itself created. It you use dependency injection that means exceptions need to be caught in create(). But create() cannot send a response to the browser, that has to happen later when the function that corresponds to the active route is called by the kernel.

My solution was to make the database service an optional parameter on the controller, and adjust the static returned by create based on the exception thrown:

<?php
  /**
 * Constructs a new DataSearchController object.
 */
public function __construct(ConfigFactory $config_factory, Connection $dataservice = null) {
  $this->config = $config_factory->get('mydataservice.datasettings');
  $this->database = $dataservice;
}

/**
 * {@inheritdoc}
 */
public static function create(ContainerInterface $container) {
    try {
      return new static(
        $container->get('config.factory'),
        $container->get('mydataservice.database')
      );
    }
    catch (\Exception $e) {
      return new static(
        $container->get('config.factory')
      );
    }

  public function getData(Request $request) {

    if (!$this->database) {
      throw new HttpException(404, $this->config->get('database_offline_message'));
    }
    $query = $this->database->select('mytable', 'mt');
    // From here you gather your data and send your response... 
  }
}

The other way to handle the exception would be to load the connection from Drupal’s service container when you need it in place of using dependency injection for that service.

Also, notice we’re throwing a 404 error. Ideally it would return a 5xx type error, but those trigger other behaviors that prevented me from providing nice errors for the JavaScript application to process easily. Our controller also had a page display (to send the JavaScript libraries and base markup for the actual interface on application startup), which meant that we needed to create a reasonably well themed response in that function as well:

<?php
    // If the database is offline, then send error message.
    if (!$this->database) {
      \Drupal::service('page_cache_kill_switch')->trigger();
      $message = $this->config->get('database_offline_message');

      $error = [
        '#theme' => 'dataservice_error_page',
        '#attributes' => [
          'class' => ['dataservice', 'database-offline'],
          'id' => 'dataservice-error',
        ],
        '#message' => [
          '#type' => 'processed_text',
          '#text' => $message['value'],
          '#format' => $message['format'],
          '#filter_types_to_skip' => [],
        ],
        '#title' => $this->t('Database Offline'),
      ];

      return $error;
    }

Settings revisited

So that fixed the errors, but still meant we had a really long wait for the database connection to time out before the connection error is even thrown in the first place. And now we come back to that PDO section of the database connection definition.

<?php
$databases['remote']['default'] = [
  'database' => 'extra_data',
  'username' => 'accessingUser',
  'password' => 'UseGoodPasswordsIn2017&Beyond',
  'prefix' => '',
  'host' => '255.255.255.255',
  'port' => '',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
  // Now is when I explain this
  'pdo' => [
    \PDO::ATTR_TIMEOUT => 5,
  ],
];

PDO expects you to override settings at connection time not in a settings file. So I couldn’t just update my PHP.ini and call it a day but I also couldn’t find any documentation on how to change any PDO settings. Leveraging the power of open source I started to follow the code paths, actually reading through how Drupal establishes MySQL connections and, found I it.

If you add a subarray in your connection definition keyed to ‘pdo’ Drupal will load and apply those settings instead of the defaults. There are a couple settings that Drupal insists on being right about for performance, stability, and security reasons, but timeout and many others are fair game.