问题来源：
使用uwsgi启动python web的时候，发现如果我的再配置里面添加相关的一些属性的
listen = 2048
的配置的时候，启动的时候总是出错，导致无法启动！
image.png
而取消后，才可以正常启动！
后来百度学习了一下原来根本的原因是：
net.core.somaxconn=128 限制了我们最大的队列请求数，而我设置已经超过了这个配置
学习目的：
参考：
（1）http://blog.csdn.net/iloveyin/article/details/45894313
（2）http://blog.csdn.net/linquidx/article/details/5914640
如果没有设置uwsgi的--listen，按网上说法是使用uwsgi启动的服务，单机最大支持并发数为100*(启动的uwsgi进程数)。
如果启动：如果启动进程为4个，则最大并发只能支持400！
1.查询设置情况：
sysctl -a | grep net.core.somaxconn
net.core.somaxconn=128
2.修改配置信息:
nano /etc/sysctl.conf
原来配置为：
# sysctl settings are defined through files in
# /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/.
#
# Vendors settings live in /usr/lib/sysctl.d/.
# To override a whole file, create a new file with the same in
# /etc/sysctl.d/ and put new settings there. To override
# only specific settings, add a file with a lexically later
# name in /etc/sysctl.d/ and put new settings there.
#
# For more information, see sysctl.conf(5) and sysctl.d(5).
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
vm.swappiness = 0
net.ipv4.neigh.default.gc_stale_time=120
# see details in https://help.aliyun.com/knowledge_detail/39428.html
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.lo.arp_announce=2
net.ipv4.conf.all.arp_announce=2
# see details in https://help.aliyun.com/knowledge_detail/41334.html
net.ipv4.tcp_max_tw_buckets = 5000
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 1024
net.ipv4.tcp_synack_retries = 2
修改后的配置为：
# sysctl settings are defined through files in
# /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/.
#
# Vendors settings live in /usr/lib/sysctl.d/.
# To override a whole file, create a new file with the same in
# /etc/sysctl.d/ and put new settings there. To override
# only specific settings, add a file with a lexically later
# name in /etc/sysctl.d/ and put new settings there.
#
# For more information, see sysctl.conf(5) and sysctl.d(5).
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
vm.swappiness = 0
net.ipv4.neigh.default.gc_stale_time=120
# see details in https://help.aliyun.com/knowledge_detail/39428.html
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.default.rp_filter=0
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.lo.arp_announce=2
net.ipv4.conf.all.arp_announce=2
net.core.somaxconn = 262144
3.然后使用
sysctl -p #重新load参数设置
4.再次查询对应的设置情况：
sysctl -a | grep net.core.somaxconn
还是128 ！！！
后来设置为 net.core.somaxconn = 2048 再保存，才可以！
查询了一下好像不知道这个是不是最大值！（如果有知道的朋友，希望能相互交流一下）
5. 再重新设置uwsgi.ini配置中的listen = 2048
6. 再次启动对应的python web服务，可以正常的运行 ！
补充：听说下面是一份完整内核优化的配置
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.tcp_max_tw_buckets = 6000
net.ipv4.tcp_sack = 1
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 16384 4194304
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.core.netdev_max_backlog = 262144
net.core.somaxconn = 262144
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_max_syn_backlog = 262144
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_synack_retries = 1
net.ipv4.tcp_syn_retries = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_fin_timeout = 1
net.ipv4.tcp_keepalive_time = 30
net.ipv4.ip_local_port_range = 1024 65000
但是上面的：net.core.somaxconn = 262144 我设置了之后 再查出来还是128 无效！不知道啥原因！是不是因为服务器的配置不一样？
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