如何从 golang 程序中设置 ulimit -n？

Question

我的目的是在 golang 程序中设置 ulimit -n，这样我就不必在全局范围内设置它，而是在程序中限制它。

找到系统调用 setrlimit 并获取相同的 rlimit。 (http://linux.die.net/man/2/setrlimit)

但是，当我尝试使用相同的示例程序时，我在设置值时收到错误提示无效参数。

package main

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)
}

得到的输出是：

george@george-Not-Specified ~/work/odesk/progium/trial $ ./getRlimit 
{4294963002032703 0}
Error Setting Rlimit  invalid argument
Rlimit Final {4294963002032703 999999}
george@george-Not-Specified ~/work/odesk/progium/trial $ sudo ./getRlimit 
[sudo] password for george: 
{4294963002032703 0}
Error Setting Rlimit  invalid argument 
Rlimit Final {4294963002032703 999999}
george@george-Not-Specified ~/work/odesk/progium/trial $ uname -a
Linux george-Not-Specified 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:32:08 UTC 2012 i686 i686 i686 GNU/Linux
george@george-Not-Specified ~/work/odesk/progium/trial $ 

所以我能够得到 rlimit 设置限制失败并返回错误。 即使它失败了，当我再次取值时 MAX 值发生了变化，但 CUR 值保持不变。 这个错误可能是由于我的内核的一些问题还是它是一个坏程序？我在哪里可以找到更多信息以及如何处理此类问题？

更新：

修复后工作。

george@george-Not-Specified ~/work/odesk/progium/trial $ go build getRlimit.go 
george@george-Not-Specified ~/work/odesk/progium/trial $ ./getRlimit 
{1024 4096}
Error Setting Rlimit  operation not permitted
Rlimit Final {1024 4096}
george@george-Not-Specified ~/work/odesk/progium/trial $ sudo ./getRlimit                                                                                               
[sudo] password for george: 
{1024 4096}
Rlimit Final {999999 999999}
george@george-Not-Specified ~/work/odesk/progium/trial $ uname -a
Linux george-Not-Specified 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:32:08 UTC 2012    i686 i686 i686 GNU/Linux
george@george-Not-Specified ~/work/odesk/progium/trial $ go version
go version devel +7c42cfa28e24 Tue Jul 30 14:22:14 2013 +1000 linux/386

Answer 1

它按预期工作。

setrlimit(2).

软限制是内核强制执行的值 对应的资源。硬限制是软限制的天花板 限制：非特权进程只能将其软限制设置为一个值 在从 0 到硬限制的范围内，并且（不可逆地）降低其 硬限制。一个特权进程（在 Linux 下：一个带有 CAP_SYS_RESOURCE 能力）可以任意更改 极限值。

rlimit.go:

package main

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)
}

输出：

$ 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}

更新：

我为linux/amd64 成功运行rlimit.go，你为linux/386 失败。对于 Linux 32 位发行版，Getrlimit 和 Setrlimit 中有一个 Go 错误。这些错误已得到修复。

使用 Go default 分支 tip（包括错误修复），运行以下命令，并使用结果更新您的问题。

$ uname -a
Linux peterSO 3.8.0-26-generic #38-Ubuntu SMP Mon Jun 17 21:46:08 UTC 2013 i686 i686 i686 GNU/Linux
$ go version
go version devel +ba52f6399462 Thu Jul 25 09:56:06 2013 -0400 linux/386
$ ulimit -Sn
1024
$ ulimit -Hn
4096
$ 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}
$