生产环境某个服务报Too many open files问题
1、首先确认允许打开的最大文件数是多少
[root@101 ~]# ulimit -a
core file size (blocks, -c) unlimited
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 15215
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 65535
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) unlimited
cpu time (seconds, -t) unlimited
max user processes (-u) 65535
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
看open files参数，结果是65535，挺大的了
2、查看系统现在打开的文件数
[root@101 ~]# lsof |wc -l
66801
3、查看java进程打开的文件数
[root@101 ~]# lsof -p 12025|wc -l
65613
12025是进程id，65613超过了系统设置的65535了
4、查看进程打开了哪些文件
[root@101 ~]# lsof -p 12025
java 12025 tomcat 92r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 93r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 94r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 95r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 96r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 97r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 98r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 99r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 100r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 101r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 102r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 103r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 104r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 105r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 106r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 107r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 108r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 109r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 110r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 111r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 112r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 113r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 114r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 115r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 116r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 117r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 118r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 119r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 120r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 121r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 122r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 123r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 124r REG 253,0 9281131 655486 /data/java/qqwry.dat
java 12025 tomcat 125r REG 253,0 9281131 655486 /data/java/qqwry.dat
发现大量打开qqwry.dat这个文件。
5、计算一下打开qqwry.dat的次数
[root@101 ~]# lsof -p 12025|grep "qqwry.dat" |wc -l
65212
打开65212次，让开发的同学去查看与这个文件相关的代码逻辑，发现这个类的逻辑里，只管打开文件，并没有关闭文件的代码逻辑，也就是打开了，并不关闭，而且每一次请求过来，就new一个这样的对象出来，很明显这样的逻辑不妥。让其不要每次都new一个对象了，建议改成单例模式。
上线后，再来看结果
[root@101 ~]# lsof -u tomcat |grep "qqwry.dat" |wc -l
1
哈哈，这个数量变成1了，爽歪歪:)
另外，发现一个博主写的关于qqwry.dat的封装类，在这里https://blog.51cto.com/binghe001/2924976，有需要的小伙伴可以参考
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