PowerShell Scripting to Replicate HDFS Data to MySQL

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

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

In order to authenticate, set the following connection properties:

• Host: Set this value to the host of your HDFS installation.
• Port: Set this value to the port of your HDFS installation. Default port: 50070

Collecting HDFS Data

1. Install the module:

   Install-Module HDFSCmdlets

2. Connect to HDFS:

   $hdfs = Connect-HDFS -Host $Host -Port $Port -Path $Path -User $User

3. Retrieve the data from a specific resource:

   $data = Select-HDFS -Connection $hdfs -Table "Files"

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

   $data = Invoke-HDFS -Connection $hdfs -Query 'SELECT * FROM Files WHERE FileId = @FileId' -Params @{'@FileId'='119116'}

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

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

Inserting HDFS 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 HDFS 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 HDFS resource (Files) and to exist in the database.

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

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

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

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