mongo集群Timeout问题

项目场景：

项目场景：springboot 项目连接阿里云 mongo。

问题描述：

再启动项目和查询mongo过程中报错：

No server chosen by ReadPreferenceServerSelector{readPreference=primary} from cluster description C
lusterDescription{type=UNKNOWN, connectionMode=MULTIPLE, serverDescriptions=[ServerDescription{address=xxx:3717, type=UNKNOWN, state=CONNECTING, excepti
on={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}, ServerDescription{address=xxx:3717, type=UNKNOWN, state=CONNECTING, excep
tion={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}]}. Waiting for 30000 ms before timing out
[2020-10-22 09:09:01.844][ERROR][unknown_8ea74c3c095b4c689a1b989f25fc6d9f][c.o.o.c.c.CRBDataQueryController]- userMobileList error 2348162338435 null 499611240792850432
org.springframework.dao.DataAccessResourceFailureException: Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}. Client view of cluster state is {type=UNKNOWN, servers=[{address=xxx:3717, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}, {address=xxx:3717, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}]; nested exception is com.mongodb.MongoTimeoutException: Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}. Client view of cluster state is {type=UNKNOWN, servers=[{address=xxx:3717, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}, {address=xxx:3717, type=UNKNOWN, state=CONNECTING, exception={com.mongodb.MongoSocketReadException: Prematurely reached end of stream}}]

解决方案：

首先报错信息是非常重要的，不要视而不见

Caused by: com.mongodb.MongoTimeoutException: Timed out after 30000 ms while waiting for a server that matches ReadPreferenceServerSelector{readPreference=primary}.

刚开始根据这关键字去查资料，网上的解决方案以下几类：

1. 设置timeout maxIdleTimeMS=3000
2. mongo java 驱动版本问题
3. 用户名密码、地址、端口等问题
4. 防火墙问题

然后一个个分析，
对于1. 确实认为大概率是这方面问题，于是根据博文解决异常：xxx,
设置了超时参数，但结果是无用。

对于2，由于使用的springboot, 1.5.3， 找到对应的MongoDB驱动版本(3.4.2)，查看MongoDB版本(3.4.6)后，去官网查看是否对应，答案是可用，所以也不是版本驱动的问题。

对于3，这个大概率不会错，但是难保万一，于是专门对了一遍用户名、密码、端口、地址，结果是没有错。

对于4，嘴不相信的，因为是运维会配置好对应的权限。结果自己去服务器尝试telnet , 发现不通， 然后找运维解决，功能正常。

结论

对于找到问题，最可以依赖的只有事实和逻辑，不要被经验主义，先入为主的观念主导，生活也是如此。