cherubimLV commented on issue #13933:
URL:
https://github.com/apache/shardingsphere/issues/13933#issuecomment-986034654
```java
@Getter
@Setter
public class WeightReplicaLoadBalanceAlgorithm implements
ReplicaLoadBalanceAlgorithm {
private static final ConcurrentHashMap<String, Double[]> WEIGHT_MAP =
new ConcurrentHashMap<>();
private Properties props = new Properties();
@Override
public Properties getProps() {
return this.props;
}
@Override
public void setProps(final Properties props) {
this.props = props;
}
@Override
public String getType() {
return "WEIGHT";
}
@Override
public String getDataSource(final String name, final String
writeDataSourceName, final List<String> readDataSourceNames) {
Double[] weight = WEIGHT_MAP.containsKey(name) ?
WEIGHT_MAP.get(name) : initWeight(readDataSourceNames);
WEIGHT_MAP.putIfAbsent(name, weight);
String dataSourceName = getDataSourceName(readDataSourceNames,
weight);
return dataSourceName;
}
private String getDataSourceName(final List<String> readDataSourceNames,
final Double[] weight) {
double randomWeight = ThreadLocalRandom.current().nextDouble(0, 1);
int index = Arrays.binarySearch(weight, randomWeight);
if (index < 0) {
index = -index - 1;
return index >= 0 && index < weight.length && randomWeight <
weight[index] ? readDataSourceNames.get(index) :
readDataSourceNames.get(readDataSourceNames.size() - 1);
} else {
return readDataSourceNames.get(index);
}
}
private Double[] initWeight(final List<String> readDataSourceNames) {
Double[] weights;
Double[] exactWeights = new Double[readDataSourceNames.size()];
Integer index = 0;
Double sum = 0D;
for (String readDataSourceName : readDataSourceNames) {
Object weightObject = props.get(readDataSourceName);
if (weightObject == null) {
throw new IllegalStateException("Read database access weight
is not configured：" + readDataSourceName);
}
Double weight;
try {
weight = Double.valueOf(weightObject.toString());
} catch (NumberFormatException e) {
throw new NumberFormatException("Read database weight
configuration error, configuration parameters:" + weightObject.toString());
}
if (Double.isInfinite(weight)) {
weight = 10000.0D;
}
if (Double.isNaN(weight)) {
weight = 1.0D;
}
exactWeights[index++] = weight;
sum += weight;
}
for (int i = 0; i < index; i++) {
if (exactWeights[i] <= 0) {
continue;
}
exactWeights[i] = exactWeights[i] / sum;
}
weights = new Double[readDataSourceNames.size()];
double randomRange = 0D;
for (int i = 0; i < index; i++) {
weights[i] = randomRange + exactWeights[i];
randomRange += exactWeights[i];
}
if (index != 0 && Math.abs(weights[index - 1] - 1.0D) >= 0.0001) {
throw new IllegalStateException("The cumulative weight is
calculated incorrectly, and the sum of the probabilities is not equal to 1.");
}
return weights;
}
}
```
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