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I'm trying to do a simple transaction using mongoose. It worked totally fine on MongoDB Atlas, but in mlab I got such an error: MongoError: Transaction numbers are only allowed on storage engines that support document-level locking. I did some research, but didn't really find any resources regarding mlab and document-level locking.
Does anyone know how to solve this problem?
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User 1 -> read request start User 2 -> read request start User 1 -> read request success (booking available) User 2 -> read request success (booking available) User 1 -> write a new record to the db (new booking) User 2 -> write a new record to the db (new booking) but this conflicts with User 1.
For situations that require atomicity of reads and writes to multiple documents (in a single or multiple collections), MongoDB supports multi-document transactions. With distributed transactions, transactions can be used across multiple operations, collections, databases, documents, and shards.
That error indicates your app/driver is attempting to use a feature that's not compatible with your Shared Cluster deployment, which employs the MMAPv1 storage einge. It's likely that you have retryable writes (https://docs.mongodb.com/manual/core/retryable-writes/) enabled. Can you try turning that feature off in the connection string (https://docs.mongodb.com/manual/reference/connection-string/#urioption.retryWrites), or directly from your driver settings?
Please let us know if you continue to experience this error after turning off this feature.
Based on this answer, I appended retryWrites=false in mongodb connection url, then it works well.
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