Why we not implement db transaction to mongodb?

[cebe]

because mongodb does not support transactions.

[TheHett]

@cebe transaction is possible on the client side, when we started to write Yii2, it had declared similar feature

[cebe]

can you point to some docs about that? I could not find any...

[TheHett]

here https://github.com/yiisoft/yii2/issues/11

[cebe]

I do not see anything about transactions in the linked docs...

[TheHett]

hmm, maybe I misunderstood

[cebe]

The list is copy from SQL layer, the question mark indicates that there was no information on whether such feature is provided by mongo or not. And as far as I know there is no such feature in mongodb. If you find it, point us to the docs and we can try implement it.

[TheHett]

Hm, maybe only Two Phase Commits http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/ but it not easy, i think

[sebathi]

https://techcrunch.com/2018/02/15/mongodb-gets-support-for-multi-document-acid-transactions/

[sebathi]

It is totally suported now.

We should be able to use them ;)

https://www.mongodb.com/transactions

[waterproofy]

It's very important update.

[devkdouglass]

Adding some examples in case anyone else runs into issues. I got hung up while trying to add the session to the $options parameter in the yii\mongodb\Collection methods.

With Yi2 Mongodb Extension

$client = Yii::$app->mongodb;
$session = $client->manager->startSession();
$session->startTransaction();

try {
    $client->createCommand()
           ->addInsert(['key' => 'value'])
           ->setWriteConcern(['session' => $session])
           ->executeBatch('COLLECTION');

    // Uncomment to prevent transaction
    // throw new \Exception('Force fail. Stop transaction.');

    $session->commitTransaction();

} catch (\Exception $error) {
    $session->abortTransaction();
    print_r($error->getMessage());
} 

Without Yii2 Mongodb Exension

$client = Yii::$app->mongodb->manager;
$session = $client->startSession();
$session->startTransaction();

try {
    $bulk = new \MongoDB\Driver\BulkWrite;
    $bulk->insert(['key' => 'value']);
    $client->executeBulkWrite('DB.COLLECTION', $bulk, ['session' => $session]);

    // Uncomment to prevent transaction
    /// throw new \Exception('Force fail. Stop transaction.');

    $session->commitTransaction();

} catch (\Exception $error) {
    $session->abortTransaction();
     print_r($error->getMessage());
}

[maharjanmilan]

$client = Yii::$app->mongodb; $session = $client->manager->startSession();

Manger is null here. Whats the issue?

[devkdouglass]

If I remember correctly and depending on your environment, you may need to install ext-mongodb to add the core API functionality, along with the MongoDB Driver. Make sure the mongodb.so extension exists in your PHP.ini file.

Also, I believe transactions are only available with Replicas(at least with Mongo Atlas) and MongoDB 4.2.