Fatal error while migrating Cosmos DB Emulator (MongoDB API) to Azure

Question

I'm having a lot of issues migrating a localhost Cosmos DB database hosted in the Cosmos DB Emulator to an online Cosmos DB instance on Azure. I have used Microsoft's data migration tool to upload the current database, converted to JSON files, to a storage account, and using a Data Migration Service to pull the data from the storage account, to the Cosmos DB database, according to the steps shown here.

At the start of the migration, i get the following fatal error:

Cannot deserialize a 'BsonDocument' from BsonType 'Array'

I don't know how to proceed. Does anyone have experience with such conversions and know how to get past this error?

Answer 1

For when others encounter this same problem in the future: I applied the following to make this work:

• Download Mongodump Full MongoDB Server download here
• Dump the Cosmos DB emulated database using mongodump
• Copy the resulting .bson and metadata files to an Azure Storage account (Blob storage)
• Get a SAS url for this account using Azure Storage Explorer
• Create a new Azure Database migration service (MongoDB => Cosmos DB (MongoDB API))
• Set Azure Storage as source, and enter the SAS url
• Set your Cosmos DB database as the target

Using mongodump, the data gets generated into a file structure which Cosmos DB understands.