客户端控制台一直报一下异常：
redis.clients.jedis.exceptions.JedisDataException: READONLY You can't write against a read only slave.
从字面意思理解的话，意思是写到了只读的从节点。正常情况下是不会出现这个问题的。只会发生在master已经切换，但是client使用的master没有刷新的情况。
可以看下jedis的源码(2.9版本)：
protected class MasterListener extends Thread {
省略一些代码...
@Override
public void run() {
running.set(true);
while (running.get()) {
j = new Jedis(host, port);
try {
// double check that it is not being shutdown
if (!running.get()) {
break;
}
j.subscribe(new JedisPubSub() {
@Override
public void onMessage(String channel, String message) {
log.fine("Sentinel " + host + ":" + port + " published: " + message + ".");
String[] switchMasterMsg = message.split(" ");
if (switchMasterMsg.length > 3) {
if (masterName.equals(switchMasterMsg[0])) {
//正常来说发生master切换，client会收到switchmaster消息，从而重新初始化连接池。 initPool(toHostAndPort(Arrays.asList(switchMasterMsg[3], switchMasterMsg[4])));
} else {
log.fine("Ignoring message on +switch-master for master name "
+ switchMasterMsg[0] + ", our master name is " + masterName);
}
} else {
log.severe("Invalid message received on Sentinel " + host + ":" + port
+ " on channel +switch-master: " + message);
}
}
}, "+switch-master");
} catch (JedisConnectionException e) {
if (running.get()) {
log.log(Level.SEVERE, "Lost connection to Sentinel at " + host + ":" + port
+ ". Sleeping 5000ms and retrying.", e);
try {
Thread.sleep(subscribeRetryWaitTimeMillis);
} catch (InterruptedException e1) {
log.log(Level.SEVERE, "Sleep interrupted: ", e1);
}
} else {
log.fine("Unsubscribing from Sentinel at " + host + ":" + port);
}
} finally {
j.close();
}
}
}
伴随着往slave节点写的错误还可以看到：
log.log(Level.SEVERE, "Lost connection to Sentinel at " + host + ":" + port
+ ". Sleeping 5000ms and retrying.", e);
这个错误日志，说明曾经客户端丢失了连接。
查看jedis github相关isuse，果真有相关内容。可以参考：
https://github.com/xetorthio/jedis/pull/1566
https://github.com/xetorthio/jedis/issues/1953
这个问题在2.9.3版本已经得到正确修复：
@Override
public void run() {
running.set(true);
while (running.get()) {
j = new Jedis(host, port);
try {
// double check that it is not being shutdown
if (!running.get()) {
break;
}
/* 这里就是关键，只要while循环一次则重新初始化一次。正常情况是会阻塞在 j.subscribe 所以不会一直执行。
* Added code for active refresh
*/
List<String> masterAddr = j.sentinelGetMasterAddrByName(masterName);
if (masterAddr == null || masterAddr.size() != 2) {
log.warning("Can not get master addr, master name: "+ masterName+". Sentinel: "+host+"："+port+".");
}else{
initPool(toHostAndPort(masterAddr));
}
//正常情况下会阻塞在这里
j.subscribe(new JedisPubSub() {
@Override
public void onMessage(String channel, String message) {
log.fine("Sentinel " + host + ":" + port + " published: " + message + ".");
String[] switchMasterMsg = message.split(" ");
if (switchMasterMsg.length > 3) {
if (masterName.equals(switchMasterMsg[0])) {
initPool(toHostAndPort(Arrays.asList(switchMasterMsg[3], switchMasterMsg[4])));
} else {
log.fine("Ignoring message on +switch-master for master name "
+ switchMasterMsg[0] + ", our master name is " + masterName);
}
} else {
log.severe("Invalid message received on Sentinel " + host + ":" + port
+ " on channel +switch-master: " + message);
}
}
}, "+switch-master");
} catch (JedisException e) {
if (running.get()) {
log.log(Level.SEVERE, "Lost connection to Sentinel at " + host + ":" + port
+ ". Sleeping 5000ms and retrying.", e);
try {
Thread.sleep(subscribeRetryWaitTimeMillis);
} catch (InterruptedException e1) {
log.log(Level.SEVERE, "Sleep interrupted: ", e1);
}
} else {
log.fine("Unsubscribing from Sentinel at " + host + ":" + port);
}
} finally {
j.close();
}
}
}
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