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) }
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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) }
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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)
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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) }
>
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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)
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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) }
>
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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。
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
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