Using the HBase Scan Operator

The <adapter-configurations> element of a project's sbconf file, despite its name, is used to specify configuration value groups for either operators or adapters.

The HBase configuration section of the sbconf file starts with an <adapter-configurations> element that contains one <adapter-configuration name="hbase"> element. This element, in turn, contains one or more <setting> elements.

Each <section name="hbase"> element must contain one element in the form <setting name="id" val="HBaseConfigName"/>, where HBaseConfigName is the name you assign to a group of settings that uniquely define an individual HBase database connection. All other <setting> elements are optional.

The example configuration below shows a basic configuration to connect to an HBase server. You can have as many configurations as your application requires, but each configuration must have a unique id.

  <adapter-configurations>
    <adapter-configuration name="hbase">
      <section name="hbase">
        <setting name="id" val="HBase Sample"/>
        <setting name="connectAtStartup" val="true" />

        <!-- All values below are passed directly to the 
             HBaseConfiguration class unmodified --/>
        <setting name="hbase.master" val="127.0.0.1:60000" />
        <setting name="hbase.zookeeper.quorum" val="127.0.0.1" />
        <setting name="hbase.zookeeper.property.clientPort" val="2181" />
        <setting name="hbase.client.retries.number" val="5" />
        <setting name="zookeeper.session.timeout" val="5000" />
        <setting name="zookeeper.recovery.retry" val="5" />
      </section>
    </adapter-configuration>
  </adapter-configurations>

Name: Use this field to specify or change the component's name, which must be unique in the application. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Operator: A read-only field that shows the formal name of the operator.

Class: A field that shows the fully qualified class name that implements the functionality of this operator. Use this class name when loading the operator in StreamSQL programs with the APPLY JAVA statement. You can right-click this field and select Copy from the context menu to place the full class name in the system clipboard.

Start with application: If this field is set to Yes or to a module parameter that evaluates to true, an instance of this operator starts as part of the containing StreamBase Server. If this field is set to No or to a module parameter that evaluates to false, the adapter is loaded with the server, but does not start until you send an sbadmin resume command, or until you start the component with StreamBase Manager. With this option set to No or false, the operator does not start even if the application as a whole is suspended and later resumed. The recommended setting is selected by default.

Enable Error Output Port: Select this check box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports and Error Streams to learn about Error Ports.

Description: Optionally enter text to briefly describe the component's purpose and function. In the EventFlow canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

Use the Concurrency tab to specify parallel regions for this instance of this component, or multiplicity options, or both. The Concurrency tab settings are described in Concurrency Options, and dispatch styles are described in Dispatch Styles.

The filter factory interface (com.streambase.sb.operator.hbase.IHBaseFilterFactory) is used to create a FilterList for an HBase Scan or Get operation. The Filter list allows HBase to return only those rows that match the criteria provided by the specified filters. The interface allows an interaction between the inbound tuple and the Scan or Get operations. See the HBase API documentation for further information about the org.apache.hadoop.hbase.filter.FilterBase class and its sub-classes, and for how-to information on filtering data.

When you have compiled a Java class to serve as a filter, provide the fully qualified name of your class in the Filter Factor Class field in the Operator Properties tab in your HBase Scan or Get operator's Properties view.

The next section provides an example class file that takes the inbound tuples and uses some of the fields of each tuple to create a filter to use for the read operation.

package com.streambase.sb.hbase.filterfactory;

import org.apache.hadoop.hbase.filter.CompareFilter.CompareOp;
import org.apache.hadoop.hbase.filter.FilterList;
import org.apache.hadoop.hbase.filter.SingleColumnValueFilter;
import org.apache.hadoop.hbase.filter.SubstringComparator;
import org.apache.hadoop.hbase.util.Bytes;

import com.streambase.sb.Tuple;
import com.streambase.sb.operator.hbase.IHBaseFilterFactory;

public class DemoFilterFactory implements IHBaseFilterFactory {

  @Override
  public FilterList createFilterList(Tuple tuple) throws Exception {
    FilterList filterList = 
      new FilterList(FilterList.Operator.MUST_PASS_ALL);
    filterList.addFilter(new 
      SingleColumnValueFilter(Bytes.toBytes(tuple.getString("family")), 
      Bytes.toBytes(tuple.getString("column")), CompareOp.EQUAL, 
      new SubstringComparator(tuple.getString("matchSubString"))));    
    return filterList;
  }
}