鸡鸡哥的nginx优化参数一backlog=8192

nginx服务器报错:
“connect() to unix:/dev/shm/fcgi.sock failed (11: Resource temporarily unavailable) while connecting to upstream”
解决:
修改
1、cat /proc/sys/net/core/somaxconn查看somaxconn的值,默认是128,
echo 8192 > /proc/sys/net/core/somaxconn,放到/etc/rc.local中
2、修改nginx配置文件,添加如下
listen 80 backlog=8192;
重启即可

网上的一篇文章:
web应用中listen函数的backlog默认会给我们内核参数的net.core.somaxconn限制到128,而nginx定义的NGX_LISTEN_BACKLOG默认为511,所以有必要调整这个值。如:
net.core.netdev_max_backlog = 262144

我们线上服务器net.core.somaxconn都是默认的128,这个参数会影响到所有AF_INET类型socket的listen队列
Man 2 listen可以知道:
int listen(int s, int backlog);

The backlog parameter defines the maximum length the queue of pending connections may grow to. If a connection request

arrives with the queue full the client may receive an error with an indication of ECONNREFUSED or, if the underlying pro-

tocol supports retransmission, the request may be ignored so that retries succeed.

BUGS

If the socket is of type AF_INET, and the backlog argument is greater than the constant SOMAXCONN (128 in Linux 2.0 &

2.2), it is silently truncated to SOMAXCONN.

也就是说,web应用中listen函数的backlog会给我们内核参数的net.core.somaxconn 限制到128,在高突发的请求中可能会导致链接超时或者触发重传
比如nginx 定义NGX_LISTEN_BACKLOG默认到511, 却由于我们参数未曾优化会限制到128,只有128个connections can be queued in kernel listen queue(by Igor Sysoev).
1.define NGX_LISTEN_BACKLOG 511/ls.backlog = NGX_LISTEN_BACKLOG;/ if (listen(s, ls.backlog) == -1) {
相信其他应用比如squid也会有类似问题,突发的大并发connect请求会由于内核listen队列的限制导致链接超时或者重传,从而影响用户体验
以下是实验测试情况,使用2台机器分别以1000个并发,benchmark方式,请求服务器 ( 相当于2000个并发请求同时请求服务器 )
情景1,默认配置, net.core.somaxconn=128,服务器为nginx

测试客户端A:
Transactions: 2072870 hits
Availability: 99.99 %
Elapsed time: 179.59 secs
Data transferred: 6096.59 MB
Response time: 0.08 secs
Transaction rate: 11542.24 trans/sec
Throughput: 33.95 MB/sec
Concurrency: 927.34
Successful transactions: 2072871
Failed transactions: 300
Longest transaction: 45.30
Shortest transaction: 0.00
错误率大概是1.5%

测试客户端B:
Transactions: 1859454 hits
Availability: 99.99 %
Elapsed time: 179.11 secs
Data transferred: 5468.90 MB
Response time: 0.09 secs
Transaction rate: 10381.63 trans/sec
Throughput: 30.53 MB/sec
Concurrency: 904.45
Successful transactions: 1859454
Failed transactions: 276
Longest transaction: 49.60
Shortest transaction: 0.00

错误率大概也是1.5%
错误提示大都为:
socket: connection timed out
warning: socket: -1803417280 select timed out: Connection timed out

情景2,调整配置, net.core.somaxconn=8192, nginx显式配置 listen 80 default backlog=8192;

测试客户端A:
** SIEGE 2.69

** Preparing 1000 concurrent users for battle.
The server is now under siege…
Lifting the server siege… done.
Transactions: 1789818 hits
Availability: 100.00 %
Elapsed time: 180.00 secs
Data transferred: 5264.09 MB
Response time: 0.10 secs
Transaction rate: 9943.43 trans/sec
Throughput: 29.24 MB/sec
Concurrency: 997.06
Successful transactions: 1789818
Failed transactions: 0
Longest transaction: 0.87
Shortest transaction: 0.00

错误率是0

测试客户端B:
** SIEGE 2.69

** Preparing 1000 concurrent users for battle.
The server is now under siege…
Lifting the server siege… done.
Transactions: 1768585 hits
Availability: 100.00 %
Elapsed time: 179.31 secs
Data transferred: 5201.65 MB
Response time: 0.10 secs
Transaction rate: 9863.28 trans/sec
Throughput: 29.01 MB/sec
Concurrency: 998.30
Successful transactions: 1768588
Failed transactions: 0
Longest transaction: 3.10
Shortest transaction: 0.03

错误率是0 nginx的配置中增加监听队列的数量,当然前提是不能超过net.core.somaxconn的值。如:
server {
listen 80 backlog=8192;
server_name http://www.linuxgit.org;
}
注:如果是多个虚拟主机,添加一个backlog即可,多了会提示重复

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嗜抽烟,嗜吃肉,常睡觉晚起,熬夜,看新闻,喜体育栏目,会操作电脑,会操作服务器,能做些别人不屑于做的事情。厌做饭,恶洗碗,不洗澡,不刷牙,不剃胡须,不喜逛超市,重压之下偶去之,无上进心,无恒心,无毅力。 1988-1998年,虚度人生 2001-2013年,懵懵懂懂忽然就有孩子有老婆有,匆匆间父亲去世,匆匆半个人生没有了 2013- 知道自己需要什么,知道自己该做什么,知道自己的是个什么样的人,重新上路,明明白白活自己。 ------鸡鸡哥 2013.02.28 老了,以后得改称老鸡鸡哥了,继续努力吧 -----鸡鸡哥 20150517
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