com.despegar.jdbc.galera.policies.RoundRobinPolicy Maven / Gradle / Ivy

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A simple Java client for MariaDB Galera Cluster and Percona XtraDB Cluster. It is designed to be an alternative to connect JVM app to MariaDB/Percona galera nodes without HAProxy

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package com.despegar.jdbc.galera.policies;

import com.despegar.jdbc.galera.NoHostAvailableException;
import com.google.common.base.MoreObjects;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Select the next active galera node
 */
public class RoundRobinPolicy implements ElectionNodePolicy {
    private static final Logger LOG = LoggerFactory.getLogger(RoundRobinPolicy.class);

    private AtomicInteger nextNodeIndex = new AtomicInteger(new Random().nextInt(997));

    @Override
    public String chooseNode(List activeNodes) {
        String selectedNode = activeNodes.get(nextNodeIndex(activeNodes));
        if (LOG.isDebugEnabled()) {
            LOG.debug("Selected roundRobin node {}", selectedNode);
        }
        return selectedNode;
    }

    @Override
    public String getName() {
        return "RoundRobin";
    }

    private int nextNodeIndex(List activeNodes) {
        int activeNodesCount = activeNodes.size();
        if (activeNodesCount == 0) {
            LOG.error("NoHostAvailableException - Active node count is zero");
            throw new NoHostAvailableException(activeNodes);
        }

        return getNextIndex() % activeNodesCount;
    }

    private int getNextIndex() {
        int nextIndex = nextNodeIndex.getAndIncrement();

        if (nextIndex > 1000000) {
            nextNodeIndex.set(0);
        }

        return nextIndex;
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(this).toString();
    }
}