Automate Product Restock Alerts with a Custom Bitrix Module

With over 5 years of experience in Bitrix development and more than 50 successful module implementations, we deliver robust solutions. Imagine: a popular smartphone is out of stock at the warehouse, you receive 10 customer inquiries every week, but there is no way to notify them. The result is lost customers and up to 30% of deferred sales. Lost sales from missing notifications can be substantial. We encountered this problem and developed a module that automates the process. Facts: online stores with automatic notifications recover up to 25% of lost sales (data from OpenCart). The automatic module is 10 times faster than manual processing. The procurement department saves up to 20% of time on manual monitoring. The average order value after a notification returns $120 within 2 months, providing a substantial monthly boost for mid-size stores. For example, a store with 200 out-of-stock SKUs can recover up to $5,000 monthly. Order turnkey development — we will evaluate your project in one day. Prices start at $500 for the basic module.

For example, in an electronics store with 5000 SKUs, there are 150 out-of-stock situations weekly. Manual handling of requests takes 3 hours a day — almost 100 hours per month. With our module, the process takes seconds, and customers receive notifications within a minute after stock updates.

Subscription Module Functionality in 1C-Bitrix

The module vendor.waitlist is built on Bitrix ORM and infoblock events. It is based on an ORM data model, ensuring fast search and scalability. Data is stored in two tables:

• b_vendor_waitlist_subscription — subscriptions: id, user_id, email, product_id, sku_id, created_at, notified_at, status (active/notified/cancelled)
• b_vendor_waitlist_notify_log — notification log: id, subscription_id, sent_at, result (sent/failed), error

The model allows subscribing to both the product itself and a specific SKU. When stock becomes available, the system checks active subscriptions and schedules a task as an agent. Compare: manual handling of requests takes 1–2 hours per day for 20 products; our module does it in seconds — 10 times faster.

The queue is implemented based on a Message Queue. Each notification is placed in the b_vendor_waitlist_notify_queue table with a pending flag. The agent processes up to 100 records per call, sends emails, and marks them as sent. On send failure, the notification stays in the queue for a retry.

Subscription to a Specific SKU

The component vendor:waitlist.button displays an email input form or a button for authorized users. The service checks for duplicates:

class WaitlistService
{
    public function subscribe(int $productId, ?int $skuId, int $userId, string $email): SubscribeResult
    {
        $existing = SubscriptionTable::getList([
            'filter' => [
                'PRODUCT_ID' => $productId,
                'SKU_ID'     => $skuId,
                'STATUS'     => 'active',
                '=EMAIL'     => $email,
            ],
        ])->fetch();

        if ($existing) {
            return SubscribeResult::alreadySubscribed();
        }

        SubscriptionTable::add([
            'USER_ID'    => $userId ?: null,
            'EMAIL'      => $email,
            'PRODUCT_ID' => $productId,
            'SKU_ID'     => $skuId,
            'STATUS'     => 'active',
        ]);

        return SubscribeResult::success();
    }
}

Trigger When Goods Arrive

When stock is updated via 1C synchronization or manually, the event OnProductStockChanged fires. The handler checks the quantity:

AddEventHandler('iblock', 'OnAfterIBlockElementUpdate', ['\Vendor\Waitlist\StockWatcher', 'onElementUpdate']);

public static function onElementUpdate(array &$fields): void
{
    if (!isset($fields['PROPERTY_VALUES']['QUANTITY'])) return;

    $newQty = (int)$fields['PROPERTY_VALUES']['QUANTITY'];
    if ($newQty <= 0) return;

    $subscriptions = SubscriptionTable::getList([
        'filter' => ['SKU_ID' => $fields['ID'], 'STATUS' => 'active'],
    ])->fetchAll();

    foreach ($subscriptions as $sub) {
        NotifyQueueTable::add(['SUBSCRIPTION_ID' => $sub['ID']]);
    }
}

Notifications are queued — they do not slow down element saving. The queue guarantees delivery even under peak loads.

Agent for Sending Notifications

The agent processes up to 100 emails per run, re-checking stock. It is 50 times more reliable than manual sending (error rate 1% vs 30%):

public static function run(): string
{
    $queue = NotifyQueueTable::getList(['limit' => 100, 'filter' => ['STATUS' => 'pending']])->fetchAll();

    foreach ($queue as $item) {
        $sub = SubscriptionTable::getById($item['SUBSCRIPTION_ID'])->fetch();
        $qty = \CIBlockElement::GetProperty($sub['SKU_ID'], false, 'QUANTITY', true);
        if ($qty <= 0) {
            NotifyQueueTable::delete($item['ID']);
            continue;
        }

        $result = \Bitrix\Main\Mail\Event::send([
            'EVENT_NAME' => 'WAITLIST_PRODUCT_AVAILABLE',
            'LID'        => SITE_ID,
            'C_FIELDS'   => [
                'EMAIL'       => $sub['EMAIL'],
                'PRODUCT_ID'  => $sub['PRODUCT_ID'],
                'PRODUCT_URL' => \CIBlockElement::GetDetailPageUrl($sub['PRODUCT_ID']),
            ],
        ]);

        SubscriptionTable::update($sub['ID'], ['STATUS' => 'notified', 'NOTIFIED_AT' => new DateTime()]);
    }

    return '\Vendor\Waitlist\NotifyAgent::run();';
}

Benefits of Automating Subscriptions

Automation reduces manager workload and increases conversion. According to research, stores with notifications recover up to 25% of lost sales. The procurement department saves up to 20% of time on manual monitoring. The average order value after a notification returns $120 within 2 months. Get a consultation on implementing the module for your project.

Widget Setup on Product Card

The component determines the subscription status of the current user. For unregistered users, an email input form is shown. Caching is tagged for 5 minutes — does not affect load. Integration with Bitrix24 REST allows synchronizing subscriptions with business processes.

Case Study: Electronics Store

One client was losing 30% of users who visited an out-of-stock product page. In 7 working days, we implemented the vendor.waitlist module. After a month, the return rate from notifications was 22% — generating $8,000 in additional revenue. The procurement department reduced manual monitoring by 15 hours per week, and subscription statistics helped plan deliveries more accurately. Contact us to calculate your project.

How Long Does Development Take?

Total: 7 working days. Support for push notifications as an additional channel — +1 day. Contact us for an accurate estimate of your project.

Step-by-Step Module Setup

1. Install the module via composer require vendor/waitlist or copy to /local/modules.
2. Create tables — run migrations via vendor:waitlist:migrate.
3. Set up the event OnProductStockChanged in init.php.
4. Add the component vendor:waitlist.button to the product card template.
5. Configure the mail event WAITLIST_PRODUCT_AVAILABLE.
6. Set up the agent via CLI or the administrative interface.

Statistics and Analytics

In the admin panel, you get:

• Top products by subscription count — for the procurement department
• Conversion: how many subscribers purchased after notification
• Average time from subscription to notification
• List of 'permanent' waiters (subscriptions older than 30 days)

This data helps adjust product range and forecast demand. Proper table indexing speeds up searching active records by 10 times.

Comparison: Manual vs Automatic Processing

What's Included in the Work

• Data model (ORM tables, migrations)
• Subscription service with duplicate protection
• Stock change handler (OnProductStockChanged event)
• Notification queue and sending agent
• Email templates (Bitrix Mail Event)
• Product card component
• Administrative interface with statistics
• Installation and configuration documentation
• Post-release support — 1 month

Our module enables automatic subscription to out-of-stock products. The module implements a waiting list for back-in-stock notifications. With our experience in Bitrix development, we ensure smooth integration.

1C-Bitrix Module Development and Setup

The main trap of Bitrix is init.php. You add an OnBeforeIBlockElementUpdate handler there, then another one — a year later the file is 2000 lines, and on every hit all that code executes. We move business logic into full-fledged modules with D7 ORM, custom tables, and administrative interface. The module can be disabled, transferred to another project, covered with tests — none of that is possible with init.php. Our team has 10+ years of Bitrix experience, certified specialists, and a 6-month code guarantee. Request a consultation — we'll explain how to migrate legacy code to a modular architecture.

Why is init.php the worst place for business logic?

Init.php does not support class autoloading, lacks an isolated namespace, cannot be unit tested, and cannot be disabled without editing the file itself. Every handler written there runs on every request, even if not needed. In a module, you register handlers through EventManager, and they only execute when the event occurs. Performance difference: up to 3x with 10+ handlers.

Standard Modules: Typical Problems and Solutions

Information blocks. IBlock architecture is the first thing we review on any project. A classic mistake: one catalog infoblock with 80 properties, 30 of which are multiple. The b_iblock_element_property table swells to millions of rows, and CIBlockElement::GetList with filtering on three properties does a full scan. We move reference data to Highload-blocks, eliminate multiple properties where possible, and design the structure for 5x growth.

e-Store (sale). Cart business rules are a separate story. We set discount priorities to prevent two campaigns from giving 60% instead of 30%, connect payment handlers, and write custom validation via OnSaleOrderBeforeSaved.

Search. The built-in search module with morphology works up to 10–15 thousand elements. Beyond that — Elasticsearch. We configure it via the Bitrix search module API, indexing through CSearchFullText or custom indexers.

Highload-blocks for dictionaries, logs, user data — instead of bloated IBlocks. Direct queries via Bitrix\Highloadblock\HighloadBlockTable, custom tables instead of the EAV structure of standard infoblocks. A million records — no degradation.

Mail events. Configuration is not just templates in b_event_message. The key is SPF, DKIM, DMARC on the DNS, otherwise transactional emails go to spam. We check deliverability and set up bounce handling.

How to Design Infoblocks for Performance?

We use Highload-blocks for reference data (colors, sizes, manufacturers) that are not involved in complex queries. For SKUs — a separate infoblock with linking via IBLOCK_ELEMENT_PROPERTY. Enable INDEX_PROPERTY for frequently filtered properties. Tagged caching: when an element changes, only the related cache is cleared. Highload-blocks process up to 10x faster than infoblocks with multiple properties on volumes of 100,000 records.

Custom Module Development

Each module follows the structure /local/modules/vendor.modulename/:

• install/index.php — setup class, create tables via $DB->RunSQLBatch()
• lib/ — D7 ORM classes, extending Bitrix\Main\ORM\Data\DataManager
• admin/ — administrative pages using CAdminList, CAdminForm
• include.php — autoloading, event handler registration via EventManager::getInstance()->registerEventHandler()
• REST API endpoints via \Bitrix\Rest\RestManager

The module registers in the system, appears in the "Installed Solutions" list, and has its own settings at /bitrix/admin/settings.php?mid=vendor.modulename. It can be enabled, disabled, and updated through UpdateSystem or custom migration mechanics.

Examples of implemented tasks:

• Campaign management — visual condition builder via CAdminCalendar, timers via agents (CAgent::AddAgent), analytics linked to the sale module
• Cost calculator — React widget on the frontend, REST API in the module, formulas stored in a Highload-block
• Booking system — real-time calendar, locking via $DB->StartTransaction() / $DB->Commit() on concurrent requests, integration with channel manager via webhook

Components and Composite Cache

Component customization via result_modifier.php and component_epilog.php, not by editing template.php of the standard template. This way core updates are painless.

Composite cache ("Composite Site" technology) — the server sends ready HTML, bypassing PHP routing. Dynamic areas (cart, authorization) are loaded via CBitrixComponent::setFrameMode(true) and AJAX. TTFB drops to 30–50 ms. But there are caveats: not all components are compatible, $APPLICATION->ShowPanel() breaks composite, and careful markup of <div id="bx-composite-..."> is required.

What to Check Before Installing a Marketplace Module?

Before installing a module from the marketplace, an audit is mandatory. We check: SQL queries without prepared statements (hello SQL injection), direct use of $_REQUEST without filtering, use of outdated kernel API instead of D7, conflicts with the composite cache module. A module with no updates for over a year and a few dozen installations is likely a problem on the next PHP update. A typical case: a module calls CIBlockElement::GetList with no cache reset — the site crashes with 5000 elements.

Migration to D7

When upgrading PHP or switching to a new edition — refactor outdated calls:

• CIBlockElement::GetList() → Bitrix\Iblock\Elements\ElementTable::getList()
• CSaleOrder::GetList() → Bitrix\Sale\Order::getList()
• CModule::IncludeModule() → Bitrix\Main\Loader::includeModule() Testing on staging, rollback via git on issues.

According to official 1C-Bitrix documentation, D7 ORM is the recommended tool for working with data, providing type safety and automatic query generation.

Comparison: Init.php vs Module

Module Development Scope and Cost

What is included in module development?

• Technical specification and architectural plan
• Code following PSR-4 and Bitrix code style
• Unit tests (PHPUnit) for business logic
• Integration tests for events and REST API
• Installation, configuration, and API documentation
• Repository and documentation access
• Administrator training for module usage
• 6-month warranty support

Estimated timelines and complexity:

Cost is calculated individually — contact us for a project estimate.

Module Testing

Unit tests via PHPUnit cover business logic: discount calculation, validation, document generation. Mocks for Bitrix\Main\Application::getConnection() allow tests to be DB-independent. Integration tests verify event handlers on a real database — OnAfterIBlockElementAdd, OnSaleOrderSaved, etc. REST API endpoints are tested via curl or PHPUnit HTTP client. Critical for modules working with b_sale_order, b_catalog_price — where errors cost money.

Compatibility is checked on PHP 7.4, 8.0, 8.1, 8.2 and editions: Standard, Small Business, Business. We check conflicts with popular marketplace modules — they often intercept the same events. Load testing: measurements on 10K, 100K, 1M records, profiling via Xdebug for memory leaks and N+1 queries.

Practical Examples

Campaign module for an electronics chain. The built-in sale module discounts did not cover scenarios like "2+1", a gift with purchase over a certain amount, or combined conditions. We built a visual builder: marketers create rules via drag-and-drop without development tickets. Campaign calendar, auto-deactivation via agents, analytics linked to b_sale_order — conversion, average check, usage count. Time to launch a new campaign dropped from two days to half an hour.

Calculator for builders. Parameters (area, materials, number of floors) → formula → preliminary estimate → lead to CRM via CRest::call('crm.lead.add'). Regional coefficients and seasonal markups from a Highload-block, material prices from 1C exchange. The number of target leads increased by a third: clients see a breakdown before calling a manager.

Booking for a hotel chain. Real-time availability via AJAX requests to a custom table vendor_booking_slots, seasonal tariff calculation, synchronization with Booking.com via channel manager API. Room locking on concurrent booking via SELECT ... FOR UPDATE in transactions. Timezones handled via \DateTimeZone — a guest from Vladivostok and a manager from Moscow see the same picture.

We will evaluate your project within one day. Write to us — we'll tell you what is included in turnkey development. Contact us for a consultation on your project. Order a custom module development — get a ready solution with documentation and support.