November 2021
Intermediate to advanced
410 pages
12h 1m
Chinese
Content preview from MongoDB权威指南（第3版）
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290
｜
第
17
章
如果有多个
mongos
进程，则可能会创建超出分片处理能力的连接：默认情况下，一个
mongos
可以接受
65 536
个连接
（与
mongod
一样），因此如果有
5
个
mongos
进程，每个
与
10 000
个客户端连接，那么这些
mongos
可能会试图创建
50 000
个到分片的连接！
为了防止这种情况发生，可以在
mongos
的命令行配置中使用
--maxConns
选项来限制其可
以创建的连接数。一个分片可以处理的单个
mongos
的最大连接数可以用以下公式来计算。
maxConns = maxConnsPrimary
−
(numMembersPerReplicaSet
×
3)
−
(other
×
3) / numMongosProcesses
以下是公式的各个部分。
maxConnsPrimary
主节点上的最大连接数，通常设置为
20 000
，以避免来自
mongos
的连接冲垮分片。
(numMembersPerReplicaSet
×
3)
主节点会与每个从节点创建一个连接，而每个从节点会与主节点创建两个连接，所以总
共有
3
个连接。
(other
×
3)
这里的其他是指可能连接到
mongods
的各种进程的数量，
比如监视或备份的代理、
shell
的直接连接（用于管理），或者为了迁移而连接到其他分片的连接。
numMongosProcesses
分片集群中
mongos
的总数。
注意，
maxConns
只会阻止
mongos
创建超过这个数量的连接。当达到这个限制时，它不会
做任何有帮助的事情：它只会阻塞请求
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