Available stock improvements

INFO

This document represents an architecture decision record (ADR) and has been mirrored from the ADR section in our Shopware 6 repository. You can find the original version here

Currently, the available stock calculation is performed on every update of a product. This is true if the product is updated via the API but also if it is ordered via the store api route. When an order is placed, this is triggered by StockUpdater::lineItemWritten and performs an update of the available stock by subtracting the stock with the quantity of open orders. If there are many open orders in the storage, this can lead to a bottleneck if many orders are executed at the same time, with the same products.

We have solved this problem by updating the available stock directly in the CheckoutOrderPlaced event with the ordered quantity:

public function orderPlaced(CheckoutOrderPlacedEvent $event): void
{
    $ids = [];
    foreach ($event->getOrder()->getLineItems() as $lineItem) {
        if ($lineItem->getType() !== LineItem::PRODUCT_LINE_ITEM_TYPE) {
            continue;
        }

        if (!\array_key_exists($lineItem->getReferencedId(), $ids)) {
            $ids[$lineItem->getReferencedId()] = 0;
        }

        $ids[$lineItem->getReferencedId()] += $lineItem->getQuantity();
    }

    // order placed event is a high load event. Because of the high load, we simply reduce the quantity here instead of executing the high costs `update` function
    $query = new RetryableQuery(
        $this->connection,
        $this->connection->prepare('UPDATE product SET available_stock = available_stock - :quantity WHERE id = :id')
    );

    foreach ($ids as $id => $quantity) {
        $query->execute(['id' => Uuid::fromHexToBytes((string) $id), 'quantity' => $quantity]);
    }

    $this->updateAvailableFlag(\array_keys($ids), $event->getContext());
}

To prevent executing the lineItemWritten logic in addition to the CheckoutOrderPlaced logic, we set a context state within the CartOrderRoute, which we can then query in the event listener and skip the process:

public function lineItemWritten(EntityWrittenEvent $event): void
{
    $ids = [];

    // we don't want to trigger to `update` method when we are inside the order process
    if ($event->getContext()->hasState('checkout-order-route')) {
        return;
    }
    
    //...
}

In addition to this optimization, we only perform a stock update if one of the three relevant fields (stock, minPurchase, isCloseout) has changed. This is checked in the ProductIndexer within the update method:

$stocks = $event->getPrimaryKeysWithPropertyChange(ProductDefinition::ENTITY_NAME, ['stock', 'isCloseout', 'minPurchase']);
$this->stockUpdater->update($stocks, $event->getContext());