如何释放MongoDB连接？
我有一个Mongo数据库服务器，它在短时间内有很多读写操作。我用Python和pymongo库来操作这个数据库。今天早上我醒来时发现，无法连接到MongoDB的主服务器，因为它的连接数达到了19992，这个数字让我有点害怕。
即使我停止了所有程序，连接数似乎也没有变化。
insert query update delete getmore command flushes mapped vsize res faults locked % idx miss % qr|qw ar|aw netIn netOut conn repl time
localhost:27417 0 0 0 0 2 1 0 624m 2.87g 287m 0 0 0 0|0 7|0 162b 1k 19992 M 10:36:16
> db.serverStatus(1)
{
"host" : "42yl:27417",
"version" : "1.8.1",
"process" : "mongod",
"uptime" : 71732,
"uptimeEstimate" : 71470,
"localTime" : ISODate("2011-05-26T03:02:48.301Z"),
"globalLock" : {
"totalTime" : 71732232290,
"lockTime" : 149471421,
"ratio" : 0.002083741384148133,
"currentQueue" : {
"total" : 0,
"readers" : 0,
"writers" : 0
},
"activeClients" : {
"total" : 7,
"readers" : 7,
"writers" : 0
}
},
"mem" : {
"bits" : 32,
"resident" : 258,
"virtual" : 910,
"supported" : true,
"mapped" : 624
},
"connections" : {
"current" : 19792,
"available" : 208
},
"extra_info" : {
"note" : "fields vary by platform",
"heap_usage_bytes" : 562688,
"page_faults" : 965
},
"indexCounters" : {
"btree" : {
"accesses" : 12789,
"hits" : 12789,
"misses" : 0,
"resets" : 0,
"missRatio" : 0
}
},
"backgroundFlushing" : {
"flushes" : 1195,
"total_ms" : 848633,
"average_ms" : 710.1531380753138,
"last_ms" : 101,
"last_finished" : ISODate("2011-05-26T03:02:18.691Z")
},
"cursors" : {
"totalOpen" : 7,
"clientCursors_size" : 7,
"timedOut" : 0
},
"network" : {
"bytesIn" : 685742402,
"bytesOut" : 2742190274,
"numRequests" : 3800041
},
"repl" : {
"ismaster" : true
},
"opcounters" : {
"insert" : 104225,
"query" : 9,
"update" : 925044,
"delete" : 45734,
"getmore" : 1642979,
"command" : 1119290
},
"asserts" : {
"regular" : 0,
"warning" : 56,
"msg" : 0,
"user" : 0,
"rollovers" : 0
},
"writeBacksQueued" : false,
"ok" : 1
}
我检查了socket连接。
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:60000 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27424 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28417 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28418 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28419 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28420 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28421 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28422 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28423 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:28424 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:38422 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:58422 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:5432 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27417 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27418 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27419 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:8443 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27420 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27421 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27422 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:27423 0.0.0.0:* LISTEN
tcp 0 0 222.73.61.42:27420 222.73.61.43:38249 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56699 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56698 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56697 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56696 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56702 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56701 ESTABLISHED
tcp 0 0 127.0.0.1:27417 127.0.0.1:56700 ESTABLISHED
tcp 0 0 222.73.61.42:27422 222.73.61.43:33616 ESTABLISHED
tcp 0 0 222.73.61.42:27417 222.73.61.43:60218 ESTABLISHED
tcp 0 0 222.73.61.42:27423 222.73.61.43:33035 ESTABLISHED
tcp 0 3324 222.73.61.42:58422 119.85.195.88:54295 ESTABLISHED
tcp 0 0 222.73.61.42:27424 222.73.61.43:55825 ESTABLISHED
tcp 0 0 222.73.61.42:54279 222.215.136.8:80 ESTABLISHED
tcp 0 0 222.73.61.42:27418 222.73.61.43:37093 ESTABLISHED
tcp 0 0 222.73.61.42:27419 222.73.61.43:38346 ESTABLISHED
tcp 0 0 127.0.0.1:56702 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56701 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56700 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56699 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56698 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56697 127.0.0.1:27417 ESTABLISHED
tcp 0 0 127.0.0.1:56696 127.0.0.1:27417 ESTABLISHED
tcp 0 0 222.73.61.42:27421 222.73.61.43:39843 ESTABLISHED
udp 0 0 0.0.0.0:48514 0.0.0.0:*
udp 0 0 222.73.61.42:50721 61.128.128.68:53 ESTABLISHED
udp 0 0 127.0.0.1:52274 127.0.0.1:52274 ESTABLISHED
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 9081684 /var/run/nscd/socket
unix 2 [ ACC ] STREAM LISTENING 18011686 /tmp/mongodb-27417.sock
unix 2 [ ACC ] STREAM LISTENING 18011689 /tmp/mongodb-27422.sock
unix 2 [ ACC ] STREAM LISTENING 18011691 /tmp/mongodb-28422.sock
unix 2 [ ACC ] STREAM LISTENING 18011697 /tmp/mongodb-27420.sock
unix 2 [ ACC ] STREAM LISTENING 18011702 /tmp/mongodb-28417.sock
unix 2 [ ACC ] STREAM LISTENING 18011693 /tmp/mongodb-27421.sock
unix 2 [ ACC ] STREAM LISTENING 18011695 /tmp/mongodb-28421.sock
unix 2 [ ACC ] STREAM LISTENING 18011699 /tmp/mongodb-28420.sock
unix 2 [ ACC ] STREAM LISTENING 18011710 /tmp/mongodb-27419.sock
unix 2 [ ACC ] STREAM LISTENING 18011713 /tmp/mongodb-28419.sock
unix 2 [ ACC ] STREAM LISTENING 18011716 /tmp/mongodb-27418.sock
unix 2 [ ACC ] STREAM LISTENING 18011719 /tmp/mongodb-28418.sock
unix 2 [ ACC ] STREAM LISTENING 18011722 /tmp/mongodb-27424.sock
unix 2 [ ACC ] STREAM LISTENING 18011725 /tmp/mongodb-28424.sock
unix 2 [ ACC ] STREAM LISTENING 18011728 /tmp/mongodb-27423.sock
unix 2 [ ACC ] STREAM LISTENING 18011731 /tmp/mongodb-28423.sock
unix 2 [ ACC ] STREAM LISTENING 12771288 /tmp/.s.PGSQL.5432
unix 2 [ ] DGRAM 3651 @/org/kernel/udev/udevd
unix 5 [ ] DGRAM 16472048 /dev/log
unix 2 [ ] STREAM CONNECTED 18706425 /var/run/nscd/socket
unix 2 [ ] DGRAM 16792651
unix 2 [ ] DGRAM 16472057
unix 2 [ ] DGRAM 16472052
4 个回答
0
如果你去到 /tmp/ 这个文件夹，你应该能看到一个叫 'mongodb-.sock' 的文件。你可以把它删掉。另外，数据库路径里可能还有一个 mongod.lock 的文件。把它删掉也能释放空间。
0
我帮你在网上查了一下，发现了MongoDB官网上有这样的内容：mongodb-docs
你可以试试这个：
waitQueueTimeoutMS=ms
"The amount of time a thread can wait for a connection to become available before timing out. This only applies if the connection pool has reached the maximum size and all connections are already in use."
或者试试这个：
waitQueueMultiple=n
"The drivers impose a limit on how many threads can be waiting for a connection at the same time. This limit is expressed as a multiple of maxPoolSize."
6
我们之前也遇到过同样的问题，我觉得这是因为Linux系统在TCP_KEEPALIVE_TIME的设置上有问题，这个设置是用来指定某个TCP连接的超时时间。对于你的情况来说，你在短时间内进行大量的读写操作，这可能会导致TCP连接的超时时间设置得更低。
你可以试试下面这个命令，可能会对你有帮助：
Checking current config:
[root@monitor-hk-1 ~]# cat /proc/sys/net/ipv4/tcp_keepalive_time
7200
Changing config:
echo 300 > /proc/sys/net/ipv4/tcp_keepalive_time
以下是我公司的一些内部备忘：
After some researching for 30,Jul's failure of mongo on testbed, ip 118.26, I found something familiar with production:
1. Total Connections reach 970+ which mongo start to block all the incoming connections.
2. Check netstat, only nearly 100 something connections are kept listening or waiting.
3. Check iostat, and cpu, memory, not a high utilization rate, several percent around 10.
Log:
Tue Jul 30 10:19:03.575 [initandlisten] connection accepted from 192.168.118.18:52858 #261673 (974 connections now open)
Tue Jul 30 10:19:03.575 [initandlisten] pthread_create failed: errno:11 Resource temporarily unavailable
Tue Jul 30 10:19:03.575 [initandlisten] can't create new thread, closing connection
After checking official manual, I found that our tcp keep-alive value may be too high:
[root@monitor-hk-1 ~]# cat /proc/sys/net/ipv4/tcp_keepalive_time
7200
I suggest to change the such value to 300 for a short keep-alive for tcp connections.
Can be done with following command:
echo 300 > /proc/sys/net/ipv4/tcp_keepalive_time
Notes: This can only change this value temporarily. If we reboot the system, it would be reset to default value. If we want to make persistent change, please reference at the Linux operation guide.
希望这些能帮到你。更多信息：