MongoDB最大连接数的查看与修改

在Linux平台下，无论是64位或者32位的MongoDB默认最大连接数都是819，WIN平台不知道.

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[root@DELL113 mongodb-linux-i686-2.4.1]# ./bin/mongo 192.168.6.42 MongoDB shell version: 2.4.1 connecting to: 192.168.6.42/test >  db.serverStatus().connections { "current" : 1, "available" : 818, "totalCreated" : NumberLong(1) }

途中available显示818少了一个，表示空闲的。current表示已经占用了的连接数，两数一加就等于819，如果我现在在连接一个，那么available就是817，current就是2

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[root@DELL113 mongodb-linux-i686-2.4.1]# ./bin/mongo 192.168.6.42 MongoDB shell version: 2.4.1 connecting to: 192.168.6.42/test >  db.serverStatus().connections { "current" : 1, "available" : 818, "totalCreated" : NumberLong(1) } > db.serverStatus().connections { "current" : 2, "available" : 817, "totalCreated" : NumberLong(2) }

819个连接数对于一般的站点我认为已经够用，并且都是现连现取现断。但这个连接数也可以修改，只要在启动的时候加入--maxConns即可

服务器启动

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[root@lee mongodb-linux-x86_64-2.4.1]# ./bin/mongod --dbpath=/root/db --maxConns=2000 Wed Apr  3 11:06:21.905 [initandlisten] MongoDB starting : pid=2812 port=27017 dbpath=/root/db 64-bit host=lee Wed Apr  3 11:06:21.957 [initandlisten] db version v2.4.1 Wed Apr  3 11:06:21.957 [initandlisten] git version: 1560959e9ce11a693be8b4d0d160d633eee75110 Wed Apr  3 11:06:21.957 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49 Wed Apr  3 11:06:21.957 [initandlisten] allocator: tcmalloc Wed Apr  3 11:06:21.957 [initandlisten] options: { dbpath: "/root/db", maxConns: 2000 } Wed Apr  3 11:06:21.982 [initandlisten] journal dir=/root/db/journal Wed Apr  3 11:06:21.982 [initandlisten] recover : no journal files present, no recovery needed Wed Apr  3 11:06:22.297 [initandlisten] preallocateIsFaster=true 2.62 Wed Apr  3 11:06:22.717 [initandlisten]  --maxConns too high, can only handle 819 Wed Apr  3 11:06:22.724 [initandlisten] waiting for connections on port 27017 Wed Apr  3 11:06:22.725 [websvr] admin web console waiting for connections on port 28017 Wed Apr  3 11:06:25.126 [initandlisten] connection accepted from 192.168.4.86:53917 #1 (1 connection now open)

查询最大连接数

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[root@DELL113 mongodb-linux-i686-2.4.1]# ./bin/mongo 192.168.6.42 MongoDB shell version: 2.4.1 connecting to: 192.168.6.42/test > db.serverStatus().connections { "current" : 1, "available" : 818, "totalCreated" : NumberLong(1) } >

发现还是819？其实是Linux默认进程能打开最大文件数有关，可以通过ulimit 解决

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[root@lee mongodb-linux-x86_64-2.4.1]# ulimit -n 2500 [root@lee mongodb-linux-x86_64-2.4.1]# ./bin/mongod --dbpath=/root/db --maxConns=2000 Wed Apr  3 11:11:07.013 [initandlisten] MongoDB starting : pid=2930 port=27017 dbpath=/root/db 64-bit host=lee Wed Apr  3 11:11:07.013 [initandlisten] db version v2.4.1 Wed Apr  3 11:11:07.013 [initandlisten] git version: 1560959e9ce11a693be8b4d0d160d633eee75110 Wed Apr  3 11:11:07.013 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49 Wed Apr  3 11:11:07.013 [initandlisten] allocator: tcmalloc Wed Apr  3 11:11:07.013 [initandlisten] options: { dbpath: "/root/db", maxConns: 2000 } Wed Apr  3 11:11:07.031 [initandlisten] journal dir=/root/db/journal Wed Apr  3 11:11:07.031 [initandlisten] recover : no journal files present, no recovery needed Wed Apr  3 11:11:07.170 [initandlisten] waiting for connections on port 27017 Wed Apr  3 11:11:07.171 [websvr] admin web console waiting for connections on port 28017 Wed Apr  3 11:11:10.076 [initandlisten] connection accepted from 192.168.4.86:53161 #1 (1 connection now open)

再查看最大连接数，搞定

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[root@DELL113 mongodb-linux-i686-2.4.1]# ./bin/mongo 192.168.6.42 MongoDB shell version: 2.4.1 connecting to: 192.168.6.42/test > db.serverStatus().connections { "current" : 1, "available" : 1999, "totalCreated" : NumberLong(1) } >

 

com.mongodb.MongoOptions的配置说明如下：

connectionsPerHost：每个主机的连接数，默认值是10。
threadsAllowedToBlockForConnectionMultiplier：线程队列数，它以上面connectionsPerHost值相乘的结果就是线程队列最大值，默认值是5。

如果连接线程排满了队列就会抛出“Out of semaphores to get db”错误。 
maxWaitTime:最大等待连接的线程阻塞时间 
connectTimeout：连接Mongo超时时间，单位：毫秒。默认为0(不超时)
socketTimeout：连接上后，读取写入数据socket超时时间。默认为0(不超时) 
autoConnectRetry：这个控制是否在一个连接时，系统会自动重试