co.cask.cdap.data2.util.hbase

Class ConfigurationTable

java.lang.Object

co.cask.cdap.data2.util.hbase.ConfigurationTable

public class ConfigurationTable
extends Object

Reads and writes current CConfiguration to a table in HBase. This make the configuration available to processes running on the HBase servers (such as coprocessors). The entire configuration is stored in a single row, keyed by the configuration type (to allow future expansion), with the configuration key as the column name, and the configuration value as the value.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ConfigurationTable.Type Defines the types of configurations to save in the table.

Constructor Summary

Constructors

Constructor and Description
ConfigurationTable(Configuration hbaseConf)

Method Summary

Methods

Modifier and Type	Method and Description
CConfiguration	read(ConfigurationTable.Type type, String sysConfigTablePrefix) Reads the given configuration type from the HBase table, looking for the HBase table name under the given "sysConfigTablePrefix".
void	write(ConfigurationTable.Type type, CConfiguration cConf) Writes the CConfiguration instance as a new row to the HBase table.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ConfigurationTable

public ConfigurationTable(Configuration hbaseConf)

Method Detail

write

public void write(ConfigurationTable.Type type,
         CConfiguration cConf)
           throws IOException

Writes the CConfiguration instance as a new row to the HBase table. The ConfigurationTable.Type given is used as the row key (allowing multiple configurations to be stored). After the new configuration is written, this will delete any configurations written with an earlier timestamp (to prevent removed values from being visible).

Parameters:

cConf - The CConfiguration instance to store

Throws:

IOException - If an error occurs while writing the configuration

read

public CConfiguration read(ConfigurationTable.Type type,
                  String sysConfigTablePrefix)
                    throws IOException

Reads the given configuration type from the HBase table, looking for the HBase table name under the given "sysConfigTablePrefix".

Parameters:

type - Type of configuration to read in

sysConfigTablePrefix - table prefix of the configuration table. (The full table name of the configuration table minus the table qualifier). Example: 'cdap.system:'

Returns:

The CConfiguration instance populated with the stored values, or null if no row was found for the given type.

Throws:

IOException - If an error occurs while attempting to read the table or the table does not exist.