PowerShell Scripting to Replicate Cassandra Data to MySQL

The CData Cmdlets for Cassandra offer live access to Cassandra 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 Cassandra and the CData Cmdlets for MySQL in PowerShell to replicate Cassandra data to a MySQL database.

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

Set the Server, Port, and Database connection properties to connect to Cassandra. Additionally, to use internal authentication set the User and Password connection properties.

Collecting Cassandra Data

1. Install the module:

   Install-Module CassandraCmdlets

2. Connect to Cassandra:

   $cassandra = Connect-Cassandra -Database $Database -Port $Port -Server $Server

3. Retrieve the data from a specific resource:

   $data = Select-Cassandra -Connection $cassandra -Table "Customer"

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

   $data = Invoke-Cassandra -Connection $cassandra -Query 'SELECT * FROM Customer WHERE FirstName = @FirstName' -Params @{'@FirstName'='Bob'}

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

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

Inserting Cassandra 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 Cassandra 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 Cassandra resource (Customer) and to exist in the database.

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

You have now replicated your Cassandra data to a MySQL database. This gives you freedom to work with Cassandra 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 Cassandra and MySQL in PowerShell, you can pipe command results to perform the replication in a single line:

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

• If you wish to replicate the Cassandra 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-Cassandra 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')}