Summary

WordPress’s built-in wp-cron.php only fires when a request hits the site. Low-traffic sites miss scheduled events; high-priority work (SMS retries, push queue draining) stalls. mam-main delegates cron to FastCron — a third-party service that pings a known AJAX endpoint on a fixed schedule, decoupling cron from site traffic.

Implementation is in includes/setcron-manager/.

Components

How sibling plugins register crons

add_filter( 'mam_cron_manager', function ( array $crons ): array {
    $crons[] = array(
        'action'    => 'my_plugin_nightly_sync', // hook id, fired via apply_filters()
        'name'      => 'Nightly Sync',           // human label for the admin grid
        'frequency' => '60',                     // interval in MINUTES
        'run_at'    => '0200',                   // optional daily time, HHMM (padded to 4)
    );
    return $crons;
} );

Each entry is an array with action (the hook id that gets fired), name (label), frequency (interval in minutes), and an optional run_at daily time. Schedules are not cron-expression syntax. The orchestrator collects entries from all subscribers; on each tick it walks the registered crons, and for each one whose stored next_run (kept in an option named after action) is overdue, it fires the hook and advances next_run by frequency minutes (or to the next run_at time).

AJAX endpoint

GET | POST  /wp-admin/admin-ajax.php?action=mam_setcron_processor

Auth: both (logged-in + nopriv) — FastCron pings as an unauthenticated request.

This is the entry point FastCron pings on every tick. The handler:

1. Resolves the active timezone (wp_timezone_string())
2. Walks the registered crons
3. For each schedule that matches “now”, invokes apply_filters( $cron_id, array() )

Per-cron callback dispatch

apply_filters( $action, array() ); // $action = sanitize_key( $cron['action'] )

Note: apply_filters (not do_action). The hook fired is the entry’s action value. The processor does use the return value — it merges last_run / next_run into it and stores the result in the option named after action — so a callback should return an array (return $data unchanged if you have nothing to persist).

Reads / writes

• Option tsl-setting-setcron-api — FastCron API token (a value of '1' is treated as disabled)
• Option tsl-setting-setcron-id — FastCron job id once created
• wp_timezone_string() — for schedule evaluation

Common cron registrations

25+ subscribers across mam-suite-hold, mam-use-case, and the sibling plugins.

Gotchas

• API-token sentinel value '1' means “feature disabled”. A real API token is a non-numeric string. Writing 1 as a token silently disables cron without an obvious error.
• FastCron pings the public site URL — if the site is behind basic auth or IP allow-list, FastCron must be allow-listed.
• Per-cron callbacks use apply_filters, not do_action — and the return value is used: the processor writes it (plus last_run / next_run) into the option named after action. Return an array (the passed-in one is fine) rather than a scalar or null.
• Time-zone handling for offsets like +05:30 falls back through two timezone_name_from_abbr attempts (DST + non-DST). Failed lookups silently fall through to UTC. Use named timezones (e.g., Asia/Kolkata) where possible.
• Callbacks are dispatched serially per tick. A long-running callback can prevent later callbacks from running on the same tick.

Related articles

• Notification queue and cron
• Recipe: Register a scheduled cron task
• Hook: mam_cron_manager

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