linux 下解决apache TIME_WAIT连接过多

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　　查看apache的连接数# netstat -n | awk ‘/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}’LAST_ACK 1SYN_RECV 164CLOSE_WAIT 3ESTABLISHED 655FIN_WAIT1 15FIN_WAIT2 81SYN_SENT 3TIME_WAIT 14274系统很多TIME_WAIT状态的连接，不能及时回收。访问量大的时候时常出现连接超时。解决办法是调整内核参数，加快TIME_WAIT状态连接的回收和启用重用。修改内核代码vi /etc/sysctl.confnet.ipv4.tcp_tw_reuse = 1 #表示开启重用。允许将TIME-WAIT sockets重新用于新的TCP连接，默认为0，表示关闭；net.ipv4.tcp_tw_recycle = 1 #表示开启TCP连接中TIME-WAIT sockets的快速回收，默认为0，表示关闭。sysctl -pvi /etc/sysctl.confnet.ipv4.tcp_tw_reuse = 1 #表示开启重用。允许将TIME-WAIT sockets重新用于新的TCP连接，默认为0，表示关闭；net.ipv4.tcp_tw_recycle = 1 #表示开启TCP连接中TIME-WAIT sockets的快速回收，默认为0，表示关闭。sysctl -p更多参数调整看以前的博客Linux web服务器常用内核参数注解调整后TIME_WAIT状态连接立即减少：# netstat -n | awk ‘/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}’LAST_ACK 9SYN_RECV 171CLOSE_WAIT 2ESTABLISHED 767FIN_WAIT1 27FIN_WAIT2 13TIME_WAIT 3675# netstat -n | awk ‘/^tcp/ {++S[$NF]} END {for(a in S) print a, S[a]}’LAST_ACK 9SYN_RECV 275CLOSE_WAIT 3ESTABLISHED 1111FIN_WAIT1 42FIN_WAIT2 154TIME_WAIT 1804在安装linux后的内核优化根据下面的选项，在优化Linux内核中要注意你修改的每一个参数，以保证万无一失.kernel.shmall = 268435456net.ipv4.tcp_syncookies = 1net.ipv4.tcp_tw_reuse = 1net.ipv4.tcp_tw_recycle = 1net.ipv4.tcp_fin_timeout = 30net.ipv4.tcp_keepalive_time = 1200net.ipv4.ip_local_port_range = 1024 65000net.ipv4.tcp_max_tw_buckets = 5000net.ipv4.tcp_max_tw_buckets = 5000net.ipv4.tcp_fin_timeout = 30net.ipv4.tcp_keepalive_time = 300net.ipv4.tcp_syncookies = 1net.ipv4.tcp_tw_reuse = 1net.ipv4.tcp_tw_recycle = 1net.ipv4.ip_local_port_range = 5000 65000net.ipv4.tcp_mem = 786432 1048576 1572864net.core.wmem_max = 873200net.core.rmem_max = 873200net.ipv4.tcp_wmem = 8192 436600 873200net.ipv4.tcp_rmem = 32768 436600 873200net.core.somaxconn = 256net.core.netdev_max_backlog = 1000net.ipv4.tcp_max_syn_backlog = 2048net.ipv4.tcp_retries2 = 5net.ipv4.tcp_keepalive_time = 500net.ipv4.tcp_keepalive_intvl = 30net.ipv4.tcp_keepalive_probes = 3net.ipv4.conf.lo.arp_ignore = 0net.ipv4.conf.lo.arp_announce = 0net.ipv4.conf.all.arp_ignore = 0net.ipv4.conf.all.arp_announce = 0各选项的解释：net.ipv4.tcp_syncookies = 1#表示开启SYN Cookies。当出现SYN等待队列溢出时，启用cookies来处理，可防范少量SYN***，默认为0，表示关闭；net.ipv4.tcp_tw_reuse = 1#表示开启重用。允许将TIME-WAIT sockets重新用于新的TCP连接，默认为0，表示关闭；net.ipv4.tcp_tw_recycle = 1#表示开启TCP连接中TIME-WAIT sockets的快速回收，默认为0，表示关闭。net.ipv4.tcp_fin_timeout = 30#表示如果套接字由本端要求关闭，这个参数决定了它保持在FIN-WAIT-2状态的时间。net.ipv4.tcp_keepalive_time = 1200#表示当keepalive起用的时候，TCP发送keepalive消息的频度。缺省是2小时，改为20分钟。net.ipv4.ip_local_port_range = 1024    65000#表示用于向外连接的端口范围。缺省情况下很小：32768到61000，改为1024到65000。net.ipv4.tcp_max_tw_buckets = 5000#表示系统同时保持TIME_WAIT套接字的最大数量，如果超过这个数字，#TIME_WAIT套接字将立刻被清除并打印警告信息。默认为180000，改为5000。#对于Apache、Nginx等服务器，上几行的参数可以很好地减少TIME_WAIT套接字数量， #但是对于Squid，效果却不大。此项参数可以控制TIME_WAIT套接字的最大数量，避免Squid服务器被大量的TIME_WAIT套接字拖死。