Issue #3138746 by jungle, rajandro, sja112, longwave, jameszhang023, quietone,...

 * Sample Database configuration format for a driver in a contributed module:

 * @code

 *   $databases['default']['default'] = [

 *     'driver' => 'mydriver',

 *     'namespace' => 'Drupal\mymodule\Driver\Database\mydriver',

 *     'autoload' => 'modules/mymodule/src/Driver/Database/mydriver/',

 *     'driver' => 'my_driver',

 *     'namespace' => 'Drupal\my_module\Driver\Database\my_driver',

 *     'autoload' => 'modules/my_module/src/Driver/Database/my_driver/',

 *     'database' => 'databasename',

 *     'username' => 'sqlusername',

 *     'password' => 'sqlpassword',

 *   be an admin path). Here's an example using the configurable_language config

 *   entity:

 *   @code

 *   mymodule.myroute:

 *     path: '/admin/mypath/{configurable_language}'

 *   my_module.my_route:

 *     path: '/admin/my-path/{configurable_language}'

 *     defaults:

 *       _controller: '\Drupal\mymodule\MyController::myMethod'

 *       _controller: '\Drupal\my_module\MyController::myMethod'

 *     options:

 *       parameters:

 *         configurable_language:

 *   arguments, but they all include an argument $container of type

 *   \Symfony\Component\DependencyInjection\ContainerInterface.

 *   If you are defining one of these classes, in the create() or

 *   createInstance() method, call $container->get('myservice.name') to

 *   createInstance() method, call $container->get('my_service.name') to

 *   instantiate a service. The results of these calls are generally passed to

 *   the class constructor and saved as member variables in the class.

 * - For functions and class methods that do not have access to either of

 * @section sec_define Defining a service

 * If your module needs to define a new service, here are the steps:

 * - Choose a unique machine name for your service. Typically, this should

 *   start with your module name. Example: mymodule.myservice.

 *   start with your module name. Example: my_module.my_service.

 * - Create a PHP interface to define what your service does.

 * - Create a default class implementing your interface that provides your

 *   service. If your class needs to use existing services (such as database

 *     array('my_function_2', array()),

 *   ),

 *   'finished' => 'my_finished_callback',

 *   'file' => 'path_to_file_containing_myfunctions',

 *   'file' => 'path_to_file_containing_my_functions',

 * );

 * batch_set($batch);

 * // Only needed if not inside a form _submit handler.

   * {@inheritdoc}

   */

  public function invalidate($cid) {

    $this->invalidatebyHash($this->normalizeCid($cid));

    $this->invalidateByHash($this->normalizeCid($cid));

  }

  /**

   * @param string $cidhash

   *   The hashed version of the original cache ID after being normalized.

   */

  protected function invalidatebyHash($cidhash) {

  protected function invalidateByHash($cidhash) {

    if ($item = $this->getByHash($cidhash)) {

      $item->expire = REQUEST_TIME - 1;

      $this->writeItem($cidhash, $item);

   */

  public function invalidateAll() {

    foreach ($this->storage()->listAll() as $cidhash) {

      $this->invalidatebyHash($cidhash);

      $this->invalidateByHash($cidhash);

    }

  }

 *   try {

 *     $id = $connection->insert('example')

 *       ->fields(array(

 *         'field1' => 'mystring',

 *         'field1' => 'string',

 *         'field2' => 5,

 *       ))

 *       ->execute();