How to configure ulimit -n effectively using Golang?

How to set ulimit -n from a golang program?

A common task in system administration is setting ulimits to control resource usage. To set the maximum number of open file descriptors (ulimit -n), you can use the setrlimit and getrlimit system calls.

<code class="go">import (
    "fmt"
    "syscall"
)

func main() {
    var rLimit syscall.Rlimit

    err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit)
    if err != nil {
        fmt.Println("Error Getting Rlimit ", err)
    }
    fmt.Println(rLimit)

    rLimit.Max = 999999
    rLimit.Cur = 999999

    err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rLimit)
    if err != nil {
        fmt.Println("Error Setting Rlimit ", err)
    }

    err = syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit)
    if err != nil {
        fmt.Println("Error Getting Rlimit ", err)
    }
    fmt.Println("Rlimit Final", rLimit)
}</code>

Understanding the output:

<code class="Bash">$ uname -a
Linux peterSO 3.8.0-26-generic #38-Ubuntu SMP Mon Jun 17 21:43:33 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
$ go build rlimit.go
$ ./rlimit
{1024 4096}
Error Setting Rlimit operation not permitted
Rlimit Final {1024 4096}
$ sudo ./rlimit
[sudo] password for peterSO:
{1024 4096}
Rlimit Final {999999 999999}</code>

The output shows the initial resource limits, the failed attempt to set the limits, and the final limits after running the program with sudo (since privileged users can modify hard limits).

Potential issues:

Note that you may encounter "operation not permitted" errors if trying to set limits without sudo. Also, ensure that you have updated your Go version to include bug fixes for Getrlimit and Setrlimit on Linux 32-bit distributions, as mentioned in the provided response.

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