如何从 golang 程序中设置 ulimit -n? [英] How to set ulimit -n from a golang program?

问题描述

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.

My purspose was to set ulimit -n from within a golang program so that I do not have to set it globally but restrict it within the program.

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

Found systemcalls setrlimit and get rlimit for the same. (http://linux.die.net/man/2/setrlimit)

但是当我尝试相同的示例程序时，我在设置值时收到错误提示无效参数.

But when I tried a sample program for the same I was getting an error saying invalid argument while setting the value.

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?

So I was able to get the rlimit Setting the limit failed and returned an error. Even though it failed the MAX value got changed when I took the value again but CUR value remains the same. Can this error be due to some issue with my kernel or is it a bad program? Where can I find more information and how to deal with an issue like this?

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

推荐答案

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.

The soft limit is the value that the kernel enforces for the corresponding resource. The hard limit acts as a ceiling for the soft limit: an unprivileged process may only set its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit. A privileged process (under Linux: one with the CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit value.

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:

我成功地为 linux/amd64 运行了 rlimit.go，而你为 linux/386 运行失败.在 Linux 32 位发行版的 Getrlimit 和 Setrlimit 中有一个 Go 错误.这些错误已得到修复.

I successfully ran rlimit.go for linux/amd64, you failed for linux/386. There were a Go bugs in Getrlimit and Setrlimit for Linux 32-bit distributions. These bugs have been fixed.

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.

Using the Go default branch tip (to include the bug fixes), run the following, and update your question with the results.

$ 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}
$ 

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