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Use the .NET SDK for Apache HBase

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Apache HBase provides two primary choices to work with your data: Apache Hive queries, and calls to the HBase REST API. You can work directly with the REST API using the curl command or a similar utility.

For C# and .NET applications, the Microsoft HBase REST Client Library for .NET provides a client library on top of the HBase REST API.

Install the SDK

The HBase .NET SDK is provided as a NuGet package, which can be installed from the Visual Studio NuGet Package Manager Console with the following command:

Install-Package Microsoft.HBase.Client

Instantiate a new HBaseClient object

To use the SDK, instantiate a new HBaseClient object, passing in ClusterCredentials composed of the Uri to your cluster, and the Hadoop user name and password.

var credentials = new ClusterCredentials(new Uri("https://CLUSTERNAME.azurehdinsight.net"), "USERNAME", "PASSWORD");
client = new HBaseClient(credentials);

Replace CLUSTERNAME with your HDInsight HBase cluster name, and USERNAME and PASSWORD with the Apache Hadoop credentials specified on cluster creation. The default Hadoop user name is admin.

Create a new table

HBase stores data in tables. A table consists of a Rowkey, the primary key, and one or more groups of columns called column families. The data in each table is horizontally distributed by a Rowkey range into regions. Each region has a start and end key. A table can have one or more regions. As the data in table grows, HBase splits large regions into smaller regions. Regions are stored in region servers, where one region server can store multiple regions.

The data is physically stored in HFiles. A single HFile contains data for one table, one region, and one column family. Rows in HFile are stored sorted on Rowkey. Each HFile has a B+ Tree index for speedy retrieval of the rows.

To create a new table, specify a TableSchema and columns. The following code checks whether the table RestSDKTable already exists - if not, the table is created.

if (!client.ListTablesAsync().Result.name.Contains("RestSDKTable"))
{
    // Create the table
    var newTableSchema = new TableSchema {name = "RestSDKTable" };
    newTableSchema.columns.Add(new ColumnSchema() {name = "t1"});
    newTableSchema.columns.Add(new ColumnSchema() {name = "t2"});

    await client.CreateTableAsync(newTableSchema);
}

This new table has two-column families, t1 and t2. Since column families are stored separately in different HFiles, it makes sense to have a separate column family for frequently queried data. In the following Insert data example, columns are added to the t1 column family.

Delete a table

To delete a table:

await client.DeleteTableAsync("RestSDKTable");

Insert data

To insert data, you specify a unique row key as the row identifier. All data is stored in a byte[] array. The following code defines and adds the title, director, and release_date columns to the t1 column family, as these columns are the most frequently accessed. The description and tagline columns are added to the t2 column family. You can partition your data into column families as needed.

var key = "fifth_element";
var row = new CellSet.Row { key = Encoding.UTF8.GetBytes(key) };
var value = new Cell
{
    column = Encoding.UTF8.GetBytes("t1:title"),
    data = Encoding.UTF8.GetBytes("The Fifth Element")
};
row.values.Add(value);
value = new Cell
{
    column = Encoding.UTF8.GetBytes("t1:director"),
    data = Encoding.UTF8.GetBytes("Luc Besson")
};
row.values.Add(value);
value = new Cell
{
    column = Encoding.UTF8.GetBytes("t1:release_date"),
    data = Encoding.UTF8.GetBytes("1997")
};
row.values.Add(value);
value = new Cell
{
    column = Encoding.UTF8.GetBytes("t2:description"),
    data = Encoding.UTF8.GetBytes("In the colorful future, a cab driver unwittingly becomes the central figure in the search for a legendary cosmic weapon to keep Evil and Mr Zorg at bay.")
};
row.values.Add(value);
value = new Cell
{
    column = Encoding.UTF8.GetBytes("t2:tagline"),
    data = Encoding.UTF8.GetBytes("The Fifth is life")
};
row.values.Add(value);

var set = new CellSet();
set.rows.Add(row);

await client.StoreCellsAsync("RestSDKTable", set);

HBase implements Cloud BigTable, so the data format looks like the following image:

Apache HBase sample data output.

Select data

To read data from an HBase table, pass the table name and row key to the GetCellsAsync method to return the CellSet.

var key = "fifth_element";

var cells = await client.GetCellsAsync("RestSDKTable", key);
// Get the first value from the row.
Console.WriteLine(Encoding.UTF8.GetString(cells.rows[0].values[0].data));
// Get the value for t1:title
Console.WriteLine(Encoding.UTF8.GetString(cells.rows[0].values
    .Find(c => Encoding.UTF8.GetString(c.column) == "t1:title").data));
// With the previous insert, it should yield: "The Fifth Element"

In this case, the code returns only the first matching row, as there should only be one row for a unique key. The returned value is changed into string format from the byte[] array. You can also convert the value to other types, such as an integer for the movie's release date:

var releaseDateField = cells.rows[0].values
    .Find(c => Encoding.UTF8.GetString(c.column) == "t1:release_date");
int releaseDate = 0;

if (releaseDateField != null)
{
    releaseDate = Convert.ToInt32(Encoding.UTF8.GetString(releaseDateField.data));
}
Console.WriteLine(releaseDate);
// Should return 1997

Scan over rows

HBase uses scan to retrieve one or more rows. This example requests multiple rows in batches of 10, and retrieves data whose key values are between 25 and 35. After retrieving all rows, delete the scanner to clean up resources.

var tableName = "mytablename";

// Assume the table has integer keys and we want data between keys 25 and 35
var scanSettings = new Scanner()
{
	batch = 10,
	startRow = BitConverter.GetBytes(25),
	endRow = BitConverter.GetBytes(35)
};
RequestOptions scanOptions = RequestOptions.GetDefaultOptions();
scanOptions.AlternativeEndpoint = "hbaserest0/";
ScannerInformation scannerInfo = null;
try
{
    scannerInfo = await client.CreateScannerAsync(tableName, scanSettings, scanOptions);
    CellSet next = null;
    while ((next = client.ScannerGetNextAsync(scannerInfo, scanOptions).Result) != null)
    {
	    foreach (var row in next.rows)
        {
            // ... read the rows
        }
    }
}
finally
{
    if (scannerInfo != null)
    {
        await client.DeleteScannerAsync(tableName, scannerInfo, scanOptions);
    }
}

Next steps