PowerShell Scripting to Replicate Cosmos DB Data to MySQL

The CData Cmdlets for Cosmos DB offer live access to Cosmos DB data from within PowerShell. Using PowerShell scripts, you can easily automate regular tasks like data replication. This article will walk through using the CData Cmdlets for Cosmos DB and the CData Cmdlets for MySQL in PowerShell to replicate Cosmos DB data to a MySQL database.

After obtaining the needed connection properties, accessing Cosmos DB data in PowerShell and preparing for replication consists of four basic steps.

To obtain the connection string needed to connect to a Cosmos DB account using the SQL API, log in to the Azure Portal, select Azure Cosmos DB, and select your account. In the Settings section, click Connection String and set the following values:

• AccountEndpoint: The Cosmos DB account URL from the Keys blade of the Cosmos DB account
• AccountKey: In the Azure portal, navigate to the Cosmos DB service and select your Azure Cosmos DB account. From the resource menu, go to the Keys page. Find the PRIMARY KEY value and set AccountKey to this value.

Collecting Cosmos DB Data

1. Install the module:

   Install-Module CosmosDBCmdlets

2. Connect to Cosmos DB:

    $cosmosdb = Connect-CosmosDB -AccountEndpoint $AccountEndpoint -AccountKey $AccountKey
    

3. Retrieve the data from a specific resource:

    $data = Select-CosmosDB -Connection $cosmosdb -Table "Customers"
    

   You can also use the Invoke-CosmosDB cmdlet to execute pure SQL-92 statements:

    $data = Invoke-CosmosDB -Connection $cosmosdb -Query 'SELECT * FROM Customers WHERE Name = @Name' -Params @{'@Name'='Morris Park Bake Shop'}
    

4. Save a list of the column names from the returned data.

    $columns = ($data | Get-Member -MemberType NoteProperty | Select-Object -Property Name).Name
    

Inserting Cosmos DB Data into the MySQL Database

With the data and column names collected, you are ready to replicate the data into a MySQL database.

1. Install the module:

   Install-Module MySQLCmdlets

2. Connect to MySQL, using the server address and port of the MySQL server, valid user credentials, and a specific database with the table in which the data will be replicated:

    $mysql = Connect-MySQL -User $User -Password $Password -Database $Database -Server $Server -Port $Port
    

3. Loop through the Cosmos DB data, store the values, and use the Add-MySQL cmdlet to insert the data into the MySQL database, one row at a time. In this example, the table will need to have the same name as the Cosmos DB resource (Customers) and to exist in the database.

    $data | % {
    $row = $_
    $values = @()
    $columns | % {
    $col = $_
    $values += $row.$($col)
    }
    Add-MySQL -Connection $mysql -Table "Customers" -Columns $columns -Values $values
    }
    

You have now replicated your Cosmos DB data to a MySQL database. This gives you freedom to work with Cosmos DB data in the same way that you work with other MySQL tables, whether that is performing analytics, building reports, or other business functions.

Notes

• Once you have connected to Cosmos DB and MySQL in PowerShell, you can pipe command results to perform the replication in a single line:

   Select-CosmosDB -Connection $cosmosdb -Table "Customers" | % {
   $row = $_
   $values = @()
   $columns | % {
   $col = $_
   $values += $row.$($col)
   }
   Add-MySQL -Connection $mysql -Table "Customers" -Columns $columns -Values $values
   }
   

• If you wish to replicate the Cosmos DB data to another database using another PowerShell module, you will want to exclude the Columns, Connection, and Table columns from the data returned by the Select-CosmosDB cmdlet since those columns are used to help pipe data from one CData cmdlet to another:

   $columns = ($data | Get-Member -MemberType NoteProperty | Select-Object -Property Name).Name | ? {$_ -NotIn @('Columns','Connection','Table')}