DBService Basic Principles

Overview

DBService is a HA storage system for relational databases, which is applicable to the scenario where a small amount of data (about 10 GB) needs to be stored, for example, component metadata. DBService can only be used by internal components of a cluster and provides data storage, query, and deletion functions.

DBService is a basic component of a cluster. Components such as Hive, Hue, Oozie, Loader, and Redis, and Loader store their metadata in DBService, and provide the metadata backup and restoration functions by using DBService.

DBService Architecture

DBService in the cluster works in active/standby mode. Two DBServer instances are deployed and each instance contains three modules: HA, Database, and FloatIP.

Figure 1 shows the DBService logical architecture.

Figure 1 DBService architecture
Click to enlarge

Table 1 describes the modules shown in Figure 1

**Table 1** Module description
Name	Description
HA	HA management module. The active/standby DBServer uses the HA module for management.
Database	Database module. This module stores the metadata of the Client module.
FloatIP	Floating IP address that provides the access function externally. It is enabled only on the active DBServer instance and is used by the Client module to access Database.
Client	Client using the DBService component, which is deployed on the component instance node. The client connects to the database by using FloatIP and then performs metadata adding, deleting, and modifying operations.