Solve Swoole service error Too many open files file handle exceeds system limit

If you encounter an Too many open files in Swoole's log, don't panic. In the process of developing TCP network applications, you often encounter the problem of Too many open files

This shows that your program has reached the maximum number of open files allowed by Linux. Need to modify ulimit settings

You can use lsof view the number of file handles opened by the process:

# 将 PID 修改为你要检查的进程ID
lsof -p PID | wc -l

You can also remove | wc -l to check the file handles opened by the service, but not closed.

You can use ulimit -n see how much the current setting is

[root@shenyan ~]# ulimit -n
100001

If it is too small, it needs to be adjusted. The Swoole document recommends that ulimit -n should be adjusted to 100000 or even larger.

So how to modify it?

ulimit -n 100000 can modify it by executing 06128beb7ec04b under the command line.

However, it should be noted that sometimes this modification method is only valid for the current terminal. Closing or reopening a terminal will restore the previous settings.

At this time, you need to modify /etc/security/limits.conf and add

* soft nofile 262140
* hard nofile 262140
root soft nofile 262140
root hard nofile 262140
* soft core unlimited
* hard core unlimited
root soft core unlimited
root hard core unlimited

After modifying the limits.conf file, you need to restart the system to take effect.

After this operation is completed, if the error Too many open files is still reported, then you can try to check the running process limit:

# 将 PID 修改为你要检查的进程ID
cat /proc/PID/limits

If the Max open files here is too small, it also needs to be modified.

Most occur in this case the use of supervisor tools such as time management, supervisor start the service default minfds configuration is 1024 , so there will be Too many open files .

The same is true when systemd LimitNOFILE needs to be modified. If not set or set to LimitNOFILE=unlimited (not recognized), the default is 1024 .

And here also pay attention to setting LimitNOFILE=infinity be equal to LimitNOFILE=65536 . For those who need more than 100,000 file openings, you must set it yourself.

In summary, the solution when Too many open files

1. ulimit -n
2. supervisor：minfds
3. systemd：LimitNOFILE