Setting up two-way synchronization between 1C and 1C-Bitrix

Configuring Bidirectional Synchronization Between 1C and 1C-Bitrix

Bidirectional synchronization is technically the most complex exchange scheme: changes in either system must reach the other without data loss and without version conflicts. Standard CommerceML partially addresses this (catalog from 1C + orders to 1C), but a fully bidirectional exchange requires clearly defined priority rules.

Priority Rules — the Foundation of Bidirectional Exchange

Answer these questions before starting development:

Violating these rules leads to data "flickering": 1C overwrites the description → an editor corrects it → 1C overwrites it again.

Implementation via Event Handlers

On the site side — controlling fields during import from 1C:

\Bitrix\Main\EventManager::getInstance()->addEventHandler(
    'iblock',
    'OnIBlockElementBeforeUpdate',
    function(\Bitrix\Main\Event $event) {
        $fields = $event->getParameter('fields');
        $elementId = $event->getParameter('id');

        // Get the list of protected fields for this element
        $protected = getProtectedFields($elementId);

        foreach ($protected as $fieldCode) {
            unset($fields[$fieldCode]);
        }

        return new \Bitrix\Main\EventResult(
            \Bitrix\Main\EventResult::SUCCESS,
            ['fields' => $fields]
        );
    }
);

Conflict Detection

A version conflict occurs when the same field has changed in both systems between exchange sessions. Detection via the timestamp of the last change:

// Store the time of the last site-side update in an additional element field
$lastSiteUpdate = $element['UF_LAST_SITE_UPDATE']; // timestamp
$lastExchangeUpdate = $element['UF_LAST_EXCHANGE_UPDATE']; // timestamp from 1C

if ($lastSiteUpdate > $lastExchangeUpdate) {
    // Field was changed on the site after the last exchange — do not overwrite
}

Case Study: Bidirectional Synchronization for a Distributor

A distribution company with 15,000 SKUs. 1C manages prices and stocks; the site manages descriptions and SEO. Twice a year — a repricing in 1C: prices change on 80% of the assortment. Before bidirectional exchange was configured, repricing would update prices but simultaneously overwrite SEO descriptions written by copywriters.

Solution: the DETAIL_TEXT field was added to the "protected list" via the custom property UF_PROTECT_DESCRIPTION. During exchange, the handler checks the flag and skips overwriting the description while applying the price update. After deployment — zero cases of SEO content loss over 8 months of operation.

Image Synchronization

Images are a separate challenge in bidirectional exchange. If 1C transmits images via CommerceML (<Картинки>) and the site has an additional gallery with retouched photos:

• Main image (PREVIEW_PICTURE) — protect if a "processed by photographer" flag is present
• Additional images from 1C — add them, but do not delete site photos

Setup Timeline