Import new and update products and their attributes with a CSV file and cron job Magento2

I understood your concern, that you want to add new products, update existing products price and product attribute value without mess up with old data.

I recommended you to create a patch command to import-products, In this patch include below conditions

1. Check Website code and Store view condition
2. Whether the product has existing or not
3. To update any data, include additional option in command line **productupdate==1** based on this condition you update the new values with old data

After checking this condition, you need to check like below sample code.

        $import_file = pathinfo($import_path);
        $import = $this->importFactory->create();
        $import->setData(
            array(
                'entity' => 'catalog_product',
                'behavior' => $import->getDefaultBehavior(),
                'validation_strategy' => 'validation-stop-on-errors',
            )
        );

        $read_file = $this->readFactory->create($import_file['dirname']);
        $csvSource = $this->csvSourceFactory->create(
            array(
                'file' => $import_file['basename'],
                'directory' => $read_file,
            )
        );
        $validate = $import->validateSource($csvSource);
        if (!$validate) {
            $output->writeln('<error>Unable to validate the CSV.</error>');
            exit;
        }

        $result = $import->importSource();
        if ($result) {
            $import->invalidateIndex();
        }

        if ($import->getCreatedItemsCount() > 0 && $productUpdate == 0) {
            $output->writeln("<info>Finished importing products from $import_path</info>");
        } else if ($import->getUpdatedItemsCount() > 0 && $productUpdate == 1) {
            $output->writeln("<info>Finished Updating the products from $import_path</info>");
        } else {
            $output->writeln("<error> Products are not created/updated, cross check the source file from $import_path</error>");
        }

Note: The CSV file should have all data of the products while import new value Ex: If you updating price value, then the CSV file the product should have all data and include with new price value. This will avoid missing data while doing update.

I am following this and its working for me.

You can create a CRON workflow and reuse the module-import-export model to import any entity.

This is an example class to define the Magento import model.

<?php


use MagentoFrameworkAppFilesystemDirectoryList;
use MagentoImportExportModelImportAdapter as ImportAdapter;
use MagentoImportExportModelImportErrorProcessingProcessingErrorAggregatorInterface;

class ImportCron
{
    const ENTITY = 'catalog_product'; //catalog_product, customer, advanced_pricing...
    const BEHAVIOR = 'append'; //append, replace, delete


    protected $importModel;

    protected $fileSystem;

    /**
     * ImportCron constructor.
     * @param MagentoImportExportModelImport $importModel
     * @param MagentoFrameworkFilesystem $filesystem
     */
    public function __construct(
        MagentoImportExportModelImport $importModel,
        MagentoFrameworkFilesystem $filesystem

    )
    {
        $this->importModel = $importModel;
        $this->fileSystem = $filesystem;
    }

    public function execute(){

        try{
            //TODO: Set Area scope, cron, adminhtml

            //TODO: Check entity, beavior, input file exist, etc...

            $fileName = '';
            $skipValidate = true;

            $sourceFile = $this->importModel->getWorkingDir() . self::ENTITY . '.csv';
            $importedFile = $this->importModel->getWorkingDir() . $fileName;
            if (strtolower($fileName) != self::ENTITY . '.csv') {
                copy($importedFile, $sourceFile);
            }

            $data = array(
                'entity' => '',
                'based_entity' => self::ENTITY,
                'behavior' => self::BEHAVIOR,
                $this->importModel::FIELD_NAME_VALIDATION_STRATEGY => $skipValidate ? ProcessingErrorAggregatorInterface::VALIDATION_STRATEGY_SKIP_ERRORS : ProcessingErrorAggregatorInterface::VALIDATION_STRATEGY_STOP_ON_ERROR,
                $this->importModel::FIELD_NAME_ALLOWED_ERROR_COUNT => 10,
                $this->importModel::FIELD_FIELD_MULTIPLE_VALUE_SEPARATOR => MagentoImportExportModelImport::DEFAULT_GLOBAL_MULTI_VALUE_SEPARATOR,
                $this->importModel::FIELD_FIELD_SEPARATOR => ',',
                $this->importModel::FIELD_NAME_IMG_FILE_DIR => 'pub/media/import'
            );


            $this->importModel->setData($data);

            $source = ImportAdapter::findAdapterFor(
                $sourceFile,
                $this->fileSystem->getDirectoryWrite(DirectoryList::ROOT),
                $data[$this->importModel::FIELD_FIELD_SEPARATOR]
            );

            $validationResult = $this->importModel->validateSource($source);

            if (!$this->importModel->getProcessedRowsCount()) {
                if (!$this->importModel->getErrorAggregator()->getErrorsCount()) {
                } else {
                    foreach ($this->importModel->getErrorAggregator()->getAllErrors() as $error) {
                        //echo error;
                    }
                }
            } else {
                $errorAggregator = $this->importModel->getErrorAggregator();
                if (!$validationResult) {
                    foreach ($errorAggregator->getRowsGroupedByErrorCode() as $errorMessage => $rows) {
                        //echo error;
                    }
                } else {
                    if ($this->importModel->isImportAllowed()) {
                        $this->importModel->importSource();
                        $errorAggregator = $this->importModel->getErrorAggregator();
                        if ($errorAggregator->hasToBeTerminated()) {
                            foreach ($errorAggregator->getRowsGroupedByErrorCode() as $errorMessage => $rows) {
                                //echo error;
                            }
                        } else {
                            $this->importModel->invalidateIndex();
                            foreach ($errorAggregator->getRowsGroupedByErrorCode() as $errorMessage => $rows) {
                                //echo error;
                            }
                        }

                        //TODO: Move source file to archive or some folder.

                    } else {
                        //file valid but could not import
                    }
                }
            }
        }
        catch (Exception $e){

        }

    }

}

Regards,