DBLE Rule.xml Configuration Guide and PatternRange Sharding Example

DBLE Project Introduction – The DBLE open‑source middleware can be explored at https://opensource.actionsky.com and its source code at https://github.com/actiontech/dble . Download releases from the GitHub releases page and join the community chat (ID: 669663113) for support.

Main Configuration Files

File

Description

server.xml

Defines DBLE server parameters such as performance, scheduled tasks, ports, and user settings; this article focuses on user access configuration.

schema.xml

Specifies table and schema definitions, dataNode relationships, and the sharding method for each table.

rule.xml

Contains the actual sharding algorithm configurations used by DBLE.

rule.xml Configuration Parsing – rule.xml is the most frequently used file when configuring sharding algorithms. A mind‑map is provided for a quick overview, but detailed semantics should be consulted in the official documentation.

rule.xml Example

Sharding can be classified into continuous and discrete types. Continuous sharding places a range of data on a single DataNode, while discrete sharding distributes data across nodes using hash or modulo methods.

Aspect

Continuous Sharding

Discrete Sharding

Advantages

Limited concurrency, low migration cost

Higher concurrency, better range‑query performance

Disadvantages

Potential data hotspots, limited concurrency

Complex data expansion, requires full redistribution

Examples

date, numberrange

hash, stringhash, patternrange

Note: If a hash or patternrange sharding interval is wide enough, it can behave like continuous sharding.

PatternRange Algorithm Example

Assume a table task_log with 10 million rows that needs to be split across three DataNodes (dn1, dn2, dn3) because single‑table queries are slow.

schema.xml entry :

<table name="task_log" dataNode="dn1,dn2,dn3" rule="three_node_range" />

rule.xml entry :

<?xml version="1.0"?>
<!DOCTYPE dble:rule SYSTEM "rule.dtd">
<dble:rule xmlns:dble="http://dble.cloud/">
  <tableRule name="three_node_range">
    <rule>
      <columns>id</columns>
      <algorithm>three_node_range</algorithm>
    </rule>
  </tableRule>
  <function name="three_node_range" class="PatternRange">
    <property name="mapFile">partition.txt</property>
    <property name="patternValue">1024</property>
    <property name="defaultNode">0</property>
  </function>
</dble:rule>

The partition.txt map file defines the node assignment:

# cat partition.txt
0-255=0
256-511=1
512-1024=2

During routing, the middleware computes M = id % patternValue. If M falls in 0‑255, the row goes to dn1; 256‑511 to dn2; 512‑1024 to dn3; otherwise it defaults to the node specified by defaultNode (dn1 in this example).

Summary – rule.xml defines the sharding algorithms actually used by DBLE. Understanding the various sharding configurations and their suitable scenarios enables users to select and configure appropriate rules, which is the first step when trying DBLE’s database‑sharding middleware.