Redis集群故障 cluster-node-timeout的慢查询导致主从切换

系统管理员 2022-05-24 01:53 376阅读 0赞

转载：http://www.jb51.net/article/125764.htm

**故障表象：**

业务层面显示提示查询redis失败

**集群组成：**

3主3从，每个节点的数据有8GB

**机器分布：**

在同一个机架中，

xx.x.xxx.199  
xx.x.xxx.200  
xx.x.xxx.201

**redis-server进程状态：**

通过命令ps -eo pid,lstart | grep $pid，

发现进程已经持续运行了3个月

**发生故障前集群的节点状态：**

xx.x.xxx.200:8371(bedab2c537fe94f8c0363ac4ae97d56832316e65) master  
xx.x.xxx.199:8373(792020fe66c00ae56e27cd7a048ba6bb2b67adb6) slave  
xx.x.xxx.201:8375(5ab4f85306da6d633e4834b4d3327f45af02171b) master  
xx.x.xxx.201:8372(826607654f5ec81c3756a4a21f357e644efe605a) slave  
xx.x.xxx.199:8370(462cadcb41e635d460425430d318f2fe464665c5) master  
xx.x.xxx.200:8374(1238085b578390f3c8efa30824fd9a4baba10ddf) slave

**---------------------------------下面是日志分析--------------------------------------**

**步1：**  
主节点8371失去和从节点8373的连接：  
46590:M 09 Sep 18:57:51.379 \# Connection with slave xx.x.xxx.199:8373 lost.

**步2：**  
主节点8370/8375判定8371失联：  
42645:M 09 Sep 18:57:50.117 \* Marking node bedab2c537fe94f8c0363ac4ae97d56832316e65 as failing (quorum reached).

**步3：**  
从节点8372/8373/8374收到主节点8375说8371失联：  
46986:S 09 Sep 18:57:50.120 \* FAIL message received from 5ab4f85306da6d633e4834b4d3327f45af02171b about bedab2c537fe94f8c0363ac4ae97d56832316e65

**步4：**  
主节点8370/8375授权8373升级为主节点转移：  
42645:M 09 Sep 18:57:51.055 \# Failover auth granted to 792020fe66c00ae56e27cd7a048ba6bb2b67adb6 for epoch 16

**步5：**  
原主节点8371修改自己的配置，成为8373的从节点：  
46590:M 09 Sep 18:57:51.488 \# Configuration change detected. Reconfiguring myself as a replica of 792020fe66c00ae56e27cd7a048ba6bb2b67adb6

**步6：**  
主节点8370/8375/8373明确8371失败状态：  
42645:M 09 Sep 18:57:51.522 \* Clear FAIL state for node bedab2c537fe94f8c0363ac4ae97d56832316e65: master without slots is reachable again.

**步7：**  
新从节点8371开始从新主节点8373，第一次全量同步数据：  
8373日志：：  
4255:M 09 Sep 18:57:51.906 \* Full resync requested by slave xx.x.xxx.200:8371  
4255:M 09 Sep 18:57:51.906 \* Starting BGSAVE for SYNC with target: disk  
4255:M 09 Sep 18:57:51.941 \* Background saving started by pid 5230  
8371日志：：  
46590:S 09 Sep 18:57:51.948 \* Full resync from master: d7751c4ebf1e63d3baebea1ed409e0e7243a4423:440721826993

**步8：**  
主节点8370/8375判定8373(新主)失联：  
42645:M 09 Sep 18:58:00.320 \* Marking node 792020fe66c00ae56e27cd7a048ba6bb2b67adb6 as failing (quorum reached).

**步9：**  
主节点8370/8375判定8373(新主)恢复：  
60295:M 09 Sep 18:58:18.181 \* Clear FAIL state for node 792020fe66c00ae56e27cd7a048ba6bb2b67adb6: is reachable again and nobody is serving its slots after some time.

**步10：**  
主节点8373完成全量同步所需要的BGSAVE操作：  
5230:C 09 Sep 18:59:01.474 \* DB saved on disk  
5230:C 09 Sep 18:59:01.491 \* RDB: 7112 MB of memory used by copy-on-write  
4255:M 09 Sep 18:59:01.877 \* Background saving terminated with success

**步11：**  
从节点8371开始从主节点8373接收到数据：  
46590:S 09 Sep 18:59:02.263 \* MASTER <-> SLAVE sync: receiving 2657606930 bytes from master

**步12：**  
主节点8373发现从节点8371对output buffer作了限制：  
4255:M 09 Sep 19:00:19.014 \# Client id=14259015 addr=xx.x.xxx.200:21772 fd=844 name= age=148 idle=148 flags=S db=0 sub=0 psub=0 multi=-1 qbuf=0 qbuf-free=0 obl=16349 oll=4103 omem=95944066 events=rw cmd=psync scheduled to be closed ASAP for overcoming of output buffer limits.  
4255:M 09 Sep 19:00:19.015 \# Connection with slave xx.x.xxx.200:8371 lost.

**步13：**  
从节点8371从主节点8373同步数据失败，连接断了，第一次全量同步失败：  
46590:S 09 Sep 19:00:19.018 \# I/O error trying to sync with MASTER: connection lost  
46590:S 09 Sep 19:00:20.102 \* Connecting to MASTER xx.x.xxx.199:8373  
46590:S 09 Sep 19:00:20.102 \* MASTER <-> SLAVE sync started

**步14：**  
从节点8371重新开始同步，连接失败，主节点8373的连接数满了：  
46590:S 09 Sep 19:00:21.103 \* Connecting to MASTER xx.x.xxx.199:8373  
46590:S 09 Sep 19:00:21.103 \* MASTER <-> SLAVE sync started  
46590:S 09 Sep 19:00:21.104 \* Non blocking connect for SYNC fired the event.  
46590:S 09 Sep 19:00:21.104 \# Error reply to PING from master: '-ERR max number of clients reached'

**步15：**  
从节点8371重新连上主节点8373，第二次开始全量同步：  
8371日志：  
46590:S 09 Sep 19:00:49.175 \* Connecting to MASTER xx.x.xxx.199:8373  
46590:S 09 Sep 19:00:49.175 \* MASTER <-> SLAVE sync started  
46590:S 09 Sep 19:00:49.175 \* Non blocking connect for SYNC fired the event.  
46590:S 09 Sep 19:00:49.176 \* Master replied to PING, replication can continue...  
46590:S 09 Sep 19:00:49.179 \* Partial resynchronization not possible (no cached master)  
46590:S 09 Sep 19:00:49.501 \* Full resync from master: d7751c4ebf1e63d3baebea1ed409e0e7243a4423:440780763454  
8373日志：  
4255:M 09 Sep 19:00:49.176 \* Slave xx.x.xxx.200:8371 asks for synchronization  
4255:M 09 Sep 19:00:49.176 \* Full resync requested by slave xx.x.xxx.200:8371  
4255:M 09 Sep 19:00:49.176 \* Starting BGSAVE for SYNC with target: disk  
4255:M 09 Sep 19:00:49.498 \* Background saving started by pid 18413  
18413:C 09 Sep 19:01:52.466 \* DB saved on disk  
18413:C 09 Sep 19:01:52.620 \* RDB: 2124 MB of memory used by copy-on-write  
4255:M 09 Sep 19:01:53.186 \* Background saving terminated with success

**步16：**  
从节点8371同步数据成功，开始加载经内存：  
46590:S 09 Sep 19:01:53.190 \* MASTER <-> SLAVE sync: receiving 2637183250 bytes from master  
46590:S 09 Sep 19:04:51.485 \* MASTER <-> SLAVE sync: Flushing old data  
46590:S 09 Sep 19:05:58.695 \* MASTER <-> SLAVE sync: Loading DB in memory

**步17：**  
集群恢复正常：  
42645:M 09 Sep 19:05:58.786 \* Clear FAIL state for node bedab2c537fe94f8c0363ac4ae97d56832316e65: slave is reachable again.

**步18：**  
从节点8371同步数据成功，耗时7分钟：  
46590:S 09 Sep 19:08:19.303 \* MASTER <-> SLAVE sync: Finished with success

**8371失联原因分析：**

由于几台机器在同一个机架，不太可能发生网络中断的情况，于是通过SLOWLOG GET命令查看了慢查询日志，发现有一个KEYS命令被执行了，耗时8.3秒，再查看集群节点超时设置，发现是5s(cluster-node-timeout 5000)

**出现节点失联的原因：**

客户端执行了耗时1条8.3s的命令，

2016/9/9 18:57:43 开始执行KEYS命令  
2016/9/9 18:57:50 8371被判断失联（redis日志）  
2016/9/9 18:57:51 执行完KEYS命令

**总结来说，有以下几个问题：**

1.由于cluster-node-timeout设置比较短，慢查询KEYS导致了集群判断节点8371失联

2.由于8371失联，导致8373升级为主，开始主从同步

3.由于配置client-output-buffer-limit的限制，导致第一次全量同步失败了

4.又由于PHP客户端的连接池有问题，疯狂连接服务器，产生了类似SYN攻击的效果

5.第一次全量同步失败后，从节点重连主节点花了30秒（超过了最大连接数1w）

**关于client-output-buffer-limit参数：**

[?][Link 1]

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     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># the soft limit is reached and remains reached for the specified number of </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># seconds (continuously). </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># So for instance if the hard limit is 32 megabytes and the soft limit is </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># 16 megabytes / 10 seconds, the client will get disconnected immediately </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># if the size of the output buffers reach 32 megabytes, but will also get </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># disconnected if the client reaches 16 megabytes and continuously overcomes </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># the limit for 10 seconds. </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># By default normal clients are not limited because they don't receive data </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># without asking (in a push way), but just after a request, so only </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># asynchronous clients may create a scenario where data is requested faster </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># than it can read. </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># Instead there is a default limit for pubsub and slave clients, since </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># subscribers and slaves receive data in a push fashion. </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;"># Both the hard or the soft limit can be disabled by setting them to zero. </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;">client-output-buffer-limit normal 0 0 0 </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;">client-output-buffer-limit slave 256mb 64mb 60 </code> 
     </div> 
     <div style="line-height:15.4px;margin:0px;padding:0px 1em;background-image:none;border:0px;float:none;height:auto;vertical-align:baseline;width:auto;min-height:auto;white-space:pre;"> 
      <code style="margin:3px auto 0px;padding:0px 0px 0px 5px;background:rgb(255,255,255);border-left:3px solid rgb(108,226,108);width:640px;font-size:14px;clear:both;border-top:0px;border-right:0px;border-bottom:0px;float:none;height:auto;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;min-height:auto;color:#000000;">client-output-buffer-limit pubsub 32mb 8mb 60</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

**采取措施：**

1.单实例的切割到4G以下，否则发生主从切换会耗时很长

2.调整client-output-buffer-limit参数，防止同步进行到一半失败

3.调整cluster-node-timeout，不能少于15s

4.禁止任何耗时超过cluster-node-timeout的慢查询，因为会导致主从切换

5.修复客户端类似SYN攻击的疯狂连接方式

**总结**

以上就是本文关于详细分析Redis集群故障的全部内容，希望对大家有所帮助。感兴趣的朋友可以参阅：[Spring AOP实现Redis缓存数据库查询源码][Spring AOP_Redis]、[简述Redis和MySQL的区别][Redis_MySQL]、[oracle 数据库启动阶段分析][oracle]等，如有不足之处，请留言之处。小编会及时更正。感谢朋友们对脚本之家网站的支持！

另外参考 ：

记一次redis主从复制client-output-buffer-limit 设置遇到的问题

http://zhmgz.lofter.com/post/90909\_bbabd6b

对于本文 ： flyer 修改

缓冲区 要做调整

client-output-buffer-limit slave 256mb 64mb 60

修改为

client-output-buffer-limit slave 0  0  0

[Link 1]: http://www.jb51.net/article/125764.htm#
[Spring AOP_Redis]: http://www.jb51.net/article/124383.htm
[Redis_MySQL]: http://www.jb51.net/article/125761.htm
[oracle]: http://www.jb51.net/article/124633.htm