序

本文主要研究一下sharding-jdbc的MasterSlaveRouter

MasterSlaveRouter

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-route/src/main/java/org/apache/shardingsphere/core/route/router/masterslave/MasterSlaveRouter.java

@RequiredArgsConstructor
public final class MasterSlaveRouter {
    
    private final MasterSlaveRule masterSlaveRule;
    
    private final boolean showSQL;
    
    /**
     * Route Master slave.
     *
     * @param sql SQL
     * @return
 
 data source names
     */
    // TODO for multiple masters may return more than one data source
    public Collection<String> route(final String sql) {
        Collection<String> result = route(new SQLJudgeEngine(sql).judge().getType());
        if (showSQL) {
            SQLLogger.logSQL(sql,result);
        }
        return
 
 result;
    }
    
    private Collection<String> route(final SQLType sqlType) {
        if (isMasterRoute(sqlType)) {
            MasterVisitedManager.setMasterVisited();
            return Collections.singletonList(masterSlaveRule.getMasterDataSourceName());
        }
        return Collections.singletonList(masterSlaveRule.getLoadBalanceAlgorithm().getDataSource(
                masterSlaveRule.getName(),masterSlaveRule.getMasterDataSourceName(),new ArrayList<>(masterSlaveRule.getSlaveDataSourceNames())));
    }
    
    private boolean isMasterRoute(final SQLType sqlType) {
        return
 
 SQLType.DQL != sqlType || MasterVisitedManager.isMasterVisited() || HintManager.isMasterRouteOnly();
    }
}
複製程式碼

• MasterSlaveRouter的route方法使用masterSlaveRule來進行路由

MasterSlaveRule

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/rule/MasterSlaveRule.java

@Getter
public class MasterSlaveRule {
    
    private final String name;
    
    private final String masterDataSourceName;
    
    private final Collection<String> slaveDataSourceNames;
    
    private final MasterSlaveLoadBalanceAlgorithm loadBalanceAlgorithm;
    
    private final MasterSlaveRuleConfiguration masterSlaveRuleConfiguration;
    
    public MasterSlaveRule(final String name,final String masterDataSourceName,final Collection<String> slaveDataSourceNames,final MasterSlaveLoadBalanceAlgorithm loadBalanceAlgorithm) {
        this.name = name;
        this.masterDataSourceName = masterDataSourceName;
        this.slaveDataSourceNames = slaveDataSourceNames;
        this.loadBalanceAlgorithm = null == loadBalanceAlgorithm ? new MasterSlaveLoadBalanceAlgorithmServiceLoader().newService() : loadBalanceAlgorithm;
        masterSlaveRuleConfiguration = new MasterSlaveRuleConfiguration(name,masterDataSourceName,slaveDataSourceNames,new LoadBalanceStrategyConfiguration(this.loadBalanceAlgorithm.getType(),this.loadBalanceAlgorithm.getProperties()));
    }
    
    public MasterSlaveRule(final MasterSlaveRuleConfiguration config) {
        name = config.getName();
        masterDataSourceName = config.getMasterDataSourceName();
        slaveDataSourceNames = config.getSlaveDataSourceNames();
        loadBalanceAlgorithm = createMasterSlaveLoadBalanceAlgorithm(config.getLoadBalanceStrategyConfiguration());
        masterSlaveRuleConfiguration = config;
    }
    
    private MasterSlaveLoadBalanceAlgorithm createMasterSlaveLoadBalanceAlgorithm(final LoadBalanceStrategyConfiguration loadBalanceStrategyConfiguration) {
        MasterSlaveLoadBalanceAlgorithmServiceLoader serviceLoader = new MasterSlaveLoadBalanceAlgorithmServiceLoader();
        return null == loadBalanceStrategyConfiguration ? serviceLoader.newService() : serviceLoader.newService(loadBalanceStrategyConfiguration.getType(),loadBalanceStrategyConfiguration.getProperties());
    }
    
    /**
     * Judge whether contain data source name.
     *
     * @param dataSourceName data source name
     * @return contain or not.
     */
    public boolean containDataSourceName(final String dataSourceName) {
        return masterDataSourceName.equals(dataSourceName) || slaveDataSourceNames.contains(dataSourceName);
    }
}
複製程式碼

• MasterSlaveRule內建了loadBalanceAlgorithm、masterSlaveRuleConfiguration

MasterSlaveLoadBalanceAlgorithm

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-api/src/main/java/org/apache/shardingsphere/spi/masterslave/MasterSlaveLoadBalanceAlgorithm.java

public interface MasterSlaveLoadBalanceAlgorithm extends TypeBasedSPI {
    
    /**
     * Get data source.
     * 
     * @param name master-slave logic data source name
     * @param masterDataSourceName name of master data sources
     * @param slaveDataSourceNames names of slave data sources
     * @return name of selected data source
     */
    String getDataSource(String name,String masterDataSourceName,List<String> slaveDataSourceNames);
}
複製程式碼

• MasterSlaveLoadBalanceAlgorithm介面繼承了TypeBasedSPI介面，它定義了getDataSource方法；它有兩個實現類分別是RandomMasterSlaveLoadBalanceAlgorithm、RoundRobinMasterSlaveLoadBalanceAlgorithm

RandomMasterSlaveLoadBalanceAlgorithm

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/strategy/masterslave/RandomMasterSlaveLoadBalanceAlgorithm.java

@Getter
@Setter
public final class RandomMasterSlaveLoadBalanceAlgorithm implements MasterSlaveLoadBalanceAlgorithm {
    
    private Properties properties = new Properties();
    
    @Override
    public String getType() {
        return "RANDOM";
    }
    
    @Override
    public String getDataSource(final String name,final List<String> slaveDataSourceNames) {
        return slaveDataSourceNames.get(new Random().nextInt(slaveDataSourceNames.size()));
    }
}
複製程式碼

• RandomMasterSlaveLoadBalanceAlgorithm使用Random().nextInt來進行隨機

RoundRobinMasterSlaveLoadBalanceAlgorithm

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/strategy/masterslave/RoundRobinMasterSlaveLoadBalanceAlgorithm.java

@Getter
@Setter
public final class RoundRobinMasterSlaveLoadBalanceAlgorithm implements MasterSlaveLoadBalanceAlgorithm {
    
    private static final ConcurrentHashMap<String,AtomicInteger> COUNTS = new ConcurrentHashMap<>();
    
    private Properties properties = new Properties();
    
    @Override
    public String getType() {
        return "ROUND_ROBIN";
    }
    
    @Override
    public String getDataSource(final String name,final List<String> slaveDataSourceNames) {
        AtomicInteger count = COUNTS.containsKey(name) ? COUNTS.get(name) : new AtomicInteger(0);
        COUNTS.putIfAbsent(name,count);
        count.compareAndSet(slaveDataSourceNames.size(),0);
        return slaveDataSourceNames.get(Math.abs(count.getAndIncrement()) % slaveDataSourceNames.size());
    }
}
複製程式碼

• RoundRobinMasterSlaveLoadBalanceAlgorithm使用Math.abs(count.getAndIncrement()) % slaveDataSourceNames.size()進行round robin

MasterSlaveRuleConfiguration

incubator-shardingsphere-4.0.0-RC1/sharding-core/sharding-core-api/src/main/java/org/apache/shardingsphere/api/config/masterslave/MasterSlaveRuleConfiguration.java

@Getter
public class MasterSlaveRuleConfiguration implements RuleConfiguration {
    
    private final String name;
    
    private final String masterDataSourceName;
    
    private final Collection<String> slaveDataSourceNames;
    
    private final LoadBalanceStrategyConfiguration loadBalanceStrategyConfiguration;
    
    public MasterSlaveRuleConfiguration(final String name,final Collection<String> slaveDataSourceNames) {
        this(name,null);
    }
    
    public MasterSlaveRuleConfiguration(final String name,final LoadBalanceStrategyConfiguration loadBalanceStrategyConfiguration) {
        Preconditions.checkArgument(!Strings.isNullOrEmpty(name),"Name is required.");
        Preconditions.checkArgument(!Strings.isNullOrEmpty(masterDataSourceName),"MasterDataSourceName is required.");
        Preconditions.checkArgument(null != slaveDataSourceNames && !slaveDataSourceNames.isEmpty(),"SlaveDataSourceNames is required.");
        this.name = name;
        this.masterDataSourceName = masterDataSourceName;
        this.slaveDataSourceNames = slaveDataSourceNames;
        this.loadBalanceStrategyConfiguration = loadBalanceStrategyConfiguration;
    }
}
複製程式碼

• MasterSlaveRuleConfiguration定義了name、masterDataSourceName、slaveDataSourceNames、loadBalanceStrategyConfiguration屬性

小結

MasterSlaveRouter的route方法使用masterSlaveRule來進行路由；MasterSlaveRule內建了loadBalanceAlgorithm、masterSlaveRuleConfiguration；MasterSlaveLoadBalanceAlgorithm介面繼承了TypeBasedSPI介面，它定義了getDataSource方法；它有兩個實現類分別是RandomMasterSlaveLoadBalanceAlgorithm、RoundRobinMasterSlaveLoadBalanceAlgorithm

doc

• MasterSlaveRouter