https://blog.csdn.net/boonya/article/details/76039070
public PhysicalDatasource
getSource() {
switch (writeType) {
case WRITE_ONLYONE_NODE: { //不区分，返回当前的，当前挂了，返回下一个
return writeSources[activedIndex];
}
case WRITE_RANDOM_NODE: { // 写操作随机发送，
int index = Math.abs(wnrandom.nextInt()) % writeSources.length;
PhysicalDatasource result = writeSources[index];
if (!this.isAlive(result)) { //当前是死的，找所有活着的，在其中随机找个
// find all live nodes
ArrayList<Integer> alives = new ArrayList<Integer>(writeSources.length - 1);
for (int i = 0; i < writeSources.length; i++) {
if (i != index) {
if (this.isAlive(writeSources[i])) {
alives.add(i);
}
}
}
if (alives.isEmpty()) {
result = writeSources[0];
} else {
// random select one
index = Math.abs(wnrandom.nextInt()) % alives.size();
result = writeSources[alives.get(index)];
}
}
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("select write source " + result.getName()
+ " for dataHost:" + this.getHostName());
}
return result;
}
default: {
throw new java.lang.IllegalArgumentException("writeType is "
+ writeType + " ,so can't return one write datasource ");
}
}
}
switch 属性：
1 表示不自动切换
2 基于mysql 主从状态决定是否切换
show slave status
3 基于mysql galary cluster 的切换机制（适合集群）
show status like 'wsrep%'
主要通过设置 activedIndex 来达到切换目的
/**
* 主从切换
*/
public boolean switchSource(int newIndex, boolean isAlarm, String reason) {
//如果write_type 不是0 ，直接返回
if (this.writeType != PhysicalDBPool.WRITE_ONLYONE_NODE || !checkIndex(newIndex)) {
return false;
}
final ReentrantLock lock = this.switchLock;
lock.lock();
try {
int current = activedIndex;
if (current != newIndex) {
// switch index
activedIndex = newIndex;
// init again 初始化数据库连接
this.init(activedIndex);
// clear all connections
this.getSources()[current].clearCons("switch datasource");
// write log
LOGGER.warn(switchMessage(current, newIndex, false, reason));
return true;
}
} finally {
lock.unlock();
}
return false;
}
/*
*
* 初始化当前的dataSource
*/
public void init(int index) {
//检查是否合法的index
if (!checkIndex(index)) {
index = 0;
}
int active = -1;
for (int i = 0; i < writeSources.length; i++) {
int j = loop(i + index);
//初始化数据库连接，由于是新切换的需要初始化 配置中的min个数据库连接
if (initSource(j, writeSources[j])) {
//不切换-1时，如果主写挂了 不允许切换过去
if(dataHostConfig.getSwitchType()==DataHostConfig.NOT_SWITCH_DS&&j>0)
{
break;
}
active = j;
activedIndex = active;
initSuccess = true;
LOGGER.info(getMessage(active, " init success"));
//保存记录到文件中
if (this.writeType == WRITE_ONLYONE_NODE) {
// only init one write datasource
MycatServer.getInstance().saveDataHostIndex(hostName, activedIndex);
break;
}
}
}
if (!checkIndex(active)) {
initSuccess = false;
StringBuilder s = new StringBuilder();
s.append(Alarms.DEFAULT).append(hostName).append(" init failure");
LOGGER.error(s.toString());
}
}