net/http: Golang socket: too many open files

Error:

[2019-05-25 10:44:08] dial tcp 127.0.0.1:5432: socket: too many open files

 

Ulimits are Linux and Unix features that allows limiting how much resources a user uses, such as processes, CPU time, and various types of memory. You can view your shell’s current ulimits with the command ulimit -a.

“Too many open files” errors happen when a process needs to open more files than it is allowed by the operating system. This number is controlled by the maximum number of file descriptors the process has.

 

Temporal solution:

The number of file descriptors for the current process can be shown with the following commands:

[root@aurlen ~]# ulimit -a | grep open
open files (-n) 1024

 

To temporal change, the number of file descriptors, execute the command ulimit -n

[root@aurlen-unix ~]# ulimit -n 614400

 

To know the limits for the current Process:

The current limits set for the process that reach that limits can be verified in the /proc file system. example the limits for Postgres:

ps aux | grep postgres


postgres 1801 0.0 0.4 369732 38592 ? S 10:43 0:08 /usr/lib/postgresql/11/bin/postgres -D /var/lib/postgresql/11/main

 

cat /proc/1801/limits

 
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            8388608              unlimited            bytes     
Max core file size        0                    unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             31219                31219                processes 
Max open files            1024                 4096                 files     
Max locked memory         16777216             16777216             bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       31219                31219                signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            

 

To change permanent.

Change or add these lines in /etc/security/limits.conf

* soft nofile 614400
* hard nofile 614400

gouser soft nofile 614400
gouser hard nofile 614400

 

* gouser is the user which run the golang server

Add or change this line to /etc/sysctl.conf

fs.file-max = 716800

 

And execute this command:

 

/sbin/sysctl -p

 

Add to the end of the file /etc/profile:

if [ $USER = "gouser" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -p 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi

Open a new terminal and execute:

ulimit -n 614400

stop and start the golang process