How can I bust the cache for the toolbar?

Question

I am creating a drupal module and here in the module file i created a check on hook_toolbar() function that if there are credentials in the database it will show 4 links in dropdown otherwise it will show only 2 links. Initially with no credentials it shows 2 links but whenever i get credentials and update them in the database i have to clear cache in order to update the tray in the hook_toolbar() in order to show 4 links.

function try_toolbar() {
    $items = [];
    \Drupal::service('page_cache_kill_switch')->trigger();
    $items['TRY'] = [
        '#cache' => [
            'contexts' => ['user.permissions'],
        ],
    ];

    if (!\Drupal::currentUser()->hasPermission('Access the Commande overview page')) {
        return $items;
    }

    $credentials = db_select('config', 'n')
        ->fields('n')
        ->condition('collection', 'TRY','=')
        ->execute()
        ->fetchAssoc();
    $opValue = $credentials['data'];
    
    if($credentials) {
        $items['TRY'] += [
            '#type' => 'toolbar_item',
            '#weight' => 1,
            'tab' => [
                '#type' => 'link',
                '#title' => 'TRY',
                '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try"),
                '#attributes' => [
                    'title' => 'try menu',
                    'class' => ['toolbar-icon', 'toolbar-icon-try'],
                ],
            ],
            'tray' => [
    
                'configuration' => [
                    '#type' => 'link',
                    '#title' => 'Dashboard',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try_dashboard"),
    
                ],[
                    '#type' => 'link',
                    '#title' => 'Notifications',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try_notifications"),
                ],[
                    '#type' => 'link',
                    '#title' => 'Settings',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try_settings"),
                ],[
                    '#type' => 'link',
                    '#title' => 'Help',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try_help"),
                ],
    
            ],
            '#attached' => array(
                'library' => array(
                    'try/admin',
                ),
            ),
    
        ];
        return $items;

    } else {
        $items['TRY'] += [
            '#type' => 'toolbar_item',
            '#weight' => 1,
            'tab' => [
                '#type' => 'link',
                '#title' => 'TRY',
                '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try"),
                '#attributes' => [
                    'title' => 'try menu',
                    'class' => ['toolbar-icon', 'toolbar-icon-try'],
                ],
            ],

            'tray' => [
    
                'configuration' => [
                    '#type' => 'link',
                    '#title' => 'On Board',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/onBoard"),
    
                ],[
                    '#type' => 'link',
                    '#title' => 'Verify Credentials',
                    '#url' => \Drupal\Core\Url::fromUri("internal:/admin/try_settings/verifyCredentials"), 
                ]
    
            ],
            '#attached' => array(
                'library' => array(
                    'try/admin',
                ),
            ),
    
        ];
        return $items;
    }
}

Here i used the following code to disable the cache

\Drupal::service('page_cache_kill_switch')->trigger();

But it is not working thus forcing me to manually clear the cache.

Please tell me a way to bust the cache depending on that database result.

Answer 1

Setting max-age to zero, as well as using the killswitch you have in your code \Drupal::service('page_cache_kill_switch')->trigger();, are both sledgehammer solutions to a problem that Drupal is built to handle with finesse. Rather than rebuilding the menu on every page load, a cache tag is added to the render array. Then when the DB credentials for that user are cleared, that cache tag is invalidated. The next time it is requested by a user who matches the invalidated cache tage, it will be rebuilt and re-cached.

You can add a cache tag to your existing cache declaration on the render array as follows:

'#cache' => [
  'contexts' => ['user.permissions'],
  // Might be 'tag' not 'tags'. I can't remember which.
  // Tag is in the format [IDENTIFIER]:[USERID].
  'tags' => 'example_credentials:' . \Drupal::currentUser()->id(),
],

Then, when the toolbar should be rebuilt, which in your case is when the user submits their new credentials to be saved, you invalidate that cache tag:

Drupal\Core\Cache\Cache::invalidateTags()

If your menu isn't user specific, but rather role specific, permission specific, or some other metric, change the references to current user ID to some other identifier that for that role, or that permission, or whatever suits your needs. If no specificity is required at all - IE the menu items should be built for all users (to whom the cache context applies), you can remove the specific identifier altogether, and just use [IDENTIFIER], which in the above example is example_credentials.