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意思就是，开头为北京的范围在A0000000~A9999999的根据后面的哈希值对5取模平均分布在0，1，2,3,4分片节点上。开头为北京的范围在B0000000以上的根据后面的哈希值对5取模平均分布在5,6,7,8,9分片节点上。开头为上海的范围在00000000~10000000的根据后面的哈希值对2取模平均分布在10,11分片节点上，剩下的开头为上海的，对6取模平均分布在10,11，12,13,14,15上。 这样，在发现某个开头的分片不够用时，可以随时改变分片规则，只要不删除之前的分片规则，就不影响以前数据的访问。在完成数据迁移后，可以删除之前的规则。 实现方法就是采用hashmap存储这些对应关系：
/**
* 首先实现不带范围约定的复合规则，即配置文件中为：
* 北京=0，1，2,3,4
* 上海=10,11
*/public class PartitionByRouteHash extends AbstractPartitionAlgorithm implements RuleAlgorithm { protected String routeFile; private Map<String, List<Integer>> routeNodeMap; protected static final String DEFAULT_NODE = "DEFAULT_NODE"; protected int keyStartIndex; protected int keyEndIndex; protected int valueStartIndex; protected int valueEndIndex; public void setKeyStartIndex(int keyStartIndex) { this.keyStartIndex = keyStartIndex;
} public void setKeyEndIndex(int keyEndIndex) { this.keyEndIndex = keyEndIndex;
} public void setValueStartIndex(int valueStartIndex) { this.valueStartIndex = valueStartIndex;
} public void setValueEndIndex(int valueEndIndex) { this.valueEndIndex = valueEndIndex;
} public void setRouteFile(String routeFile) { this.routeFile = routeFile;
}
@Override public void init() {
initialize();
}
@Override public Integer calculate(String columnValue) {
String key = columnValue.substring(keyStartIndex,keyEndIndex);
String value = columnValue.substring(valueStartIndex,valueEndIndex);
List<Integer> nodes = routeNodeMap.get(key); if(nodes == null)
nodes = routeNodeMap.get(DEFAULT_NODE);
BigInteger bigNum = new BigInteger(""+value.hashCode()); return nodes.get((bigNum.mod(BigInteger.valueOf(nodes.size()))).intValue());
} /**
* 读取文件，创建哈希表保存对应关系
*/
private void initialize() {
BufferedReader in = null; try { // FileInputStream fin = new FileInputStream(new File(fileMapPath));
InputStream fin = this.getClass().getClassLoader()
.getResourceAsStream(routeFile); if (fin == null) { throw new RuntimeException("can't find class resource file "
+ routeFile);
} in = new BufferedReader(new InputStreamReader(fin));
routeNodeMap = new HashMap<String, List<Integer>>(); for (String line = null; (line = in.readLine()) != null;) {
line = line.trim(); if (line.startsWith("#") || line.startsWith("//")) continue; int ind = line.indexOf('='); if (ind < 0) continue; try {
String key = line.substring(0, ind).trim();
String value = line.substring(ind+1).trim();
String []nodes = value.split(",");
List<Integer> values = new ArrayList<Integer>(); for(int i = 0 ; i< nodes.length ; i++){
values.add(Integer.parseInt(nodes[i].trim()));
}
routeNodeMap.put(key,values);
} catch (Exception e) {
System.out.println("something wrong in the route hash configuration!");
}
}
} catch (Exception e) { if (e instanceof RuntimeException) { throw (RuntimeException) e;
} else { throw new RuntimeException(e);
}
} finally { try { in.close();
} catch (Exception e2) {
}
}
}
}/**
* 实现范围约定的复合规则
*/public class PartitionByScalableRouteHash extends PartitionByRouteHash { private Map<String,Map<String[],List<Integer>>> routeNodeMap;
@Override public void init() {
initialize();
}
@Override public Integer calculate(String columnValue) {
String key = columnValue.substring(keyStartIndex,keyEndIndex);
String value = columnValue.substring(valueStartIndex,valueEndIndex);
Map<String[],List<Integer>> scaleMap = routeNodeMap.get(key); if(scaleMap==null){
scaleMap = routeNodeMap.get(this.DEFAULT_NODE);
}
String []ranges = new String[1]; for(String []range:scaleMap.keySet()){ if(range[0].equals(this.DEFAULT_NODE)) continue; if(range[0].compareTo(value)<0&&range[1].compareTo(value)>0)
ranges = range;
} if(ranges.length==1) { for(String []range:scaleMap.keySet()){ if(range[0].equals(this.DEFAULT_NODE)){
ranges = range; break;
}
}
}
List<Integer> nodes = scaleMap.get(ranges);
BigInteger bigNum = new BigInteger(""+value.hashCode()); return nodes.get((bigNum.mod(BigInteger.valueOf(nodes.size()))).intValue());
} private void initialize(){
BufferedReader in = null; try { // FileInputStream fin = new FileInputStream(new File(fileMapPath));
InputStream fin = this.getClass().getClassLoader()
.getResourceAsStream(routeFile); if (fin == null) { throw new RuntimeException("can't find class resource file "
+ routeFile);
} in = new BufferedReader(new InputStreamReader(fin));
routeNodeMap = new HashMap<String, Map<String[], List<Integer>>>(); for (String line = null; (line = in.readLine()) != null;) {
line = line.trim(); if (line.startsWith("#") || line.startsWith("//")) continue; int lb = line.indexOf('('),rb = line.indexOf(')'),mb = line.indexOf(':'); int ind = line.indexOf('='); if((lb!=-1&&rb!=-1&&mb!=-1)&&(mb<lb||mb>rb||lb>rb||rb>ind)){ throw new RuntimeException("Wrong format! Error use of (),:,=!");
} if (ind < 0) continue; try {
String key = line.substring(0, lb<0?ind:lb).trim();
Map<String[],List<Integer>> scaleMap = routeNodeMap.get(key); if(scaleMap == null){
scaleMap = new HashMap<String[],List<Integer>>();
routeNodeMap.put(key,scaleMap);
}
String[] valueRange = new String[2]; if(lb!=-1&&rb!=-1&&mb!=-1) {
String minValue = line.substring(lb + 1, mb).trim();
String maxValue = line.substring(mb + 1, rb).trim(); if (minValue.length() != maxValue.length() || minValue.compareTo(maxValue) >= 0) { throw new RuntimeException("Wrong value range! ");
}
valueRange[0] = minValue;
valueRange[1] = maxValue;
} else {
valueRange[0] = this.DEFAULT_NODE;
}
String value = line.substring(ind+1).trim();
String []nodes = value.split(",");
List<Integer> node = new ArrayList<Integer>(); for(int i = 0 ; i< nodes.length ; i++){
node.add(Integer.parseInt(nodes[i].trim()));
}
scaleMap.put(valueRange,node);
} catch (Exception e) {
System.out.println("something wrong in the route hash configuration!");
}
}
} catch (Exception e) { if (e instanceof RuntimeException) { throw (RuntimeException) e;
} else { throw new RuntimeException(e);
}
} finally { try { in.close();
} catch (Exception e2) {
}
}
}
}之后如果想用这个规则，在rule.xml中添加如下配置即可：
<tableRule name="scalable-route-hash"> <rule> <columns>order_id</columns> <algorithm>scalable-route-hash</algorithm> </rule> </tableRule> <function name="scalable-route-hash" class="org.opencloudb.route.function.PartitionByRouteHash"> <property name="routeFile">scalable-route-hash.txt</property> <property name="keyStartIndex">0</property> <property name="keyEndIndex">5</property> <property name="valueStartIndex">5</property> <property name="valueEndIndex">11</property> </function>
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