为什么此 Elixir 脚本在完成其工作之前退出？

Question

我在 Elixir 脚本中编写了一个模块 SC，

wget.exs

。模块

SC

利用Erlang的OS模块来执行复杂的命令并将其输出打印在屏幕上。我使用脚本中的模块通过

wget

:

一次下载多个包

#!/usr/bin/env elixir

defmodule SC do
  def run(cmmnd) do
    output = :os.cmd(String.to_charlist(cmmnd))    
    IO.puts output
  end
end

defmodule Downloader do
  def download_packages do
    lst_f_pckgs = "wget-list-sysv"

    #System.cmd("wget", ["https://www.linuxfromscratch.org/lfs/view/stable/#{lst_f_pckgs}"])
    SC.run("wget -c https://www.linuxfromscratch.org/lfs/view/stable/#{lst_f_pckgs}")
    
    {:ok, file_content} = File.read(lst_f_pckgs)
    arr_f_pckgs = String.split(file_content, ~r/\s+/)

    tasks =
      arr_f_pckgs
      |> Enum.map(fn l ->
        #Task.async(fn -> System.cmd("wget", [l]) end)
        Task.async(fn -> SC.run("wget -c #{l}") end)
      end)

    tasks
    |> Enum.each(&Task.await/1)

    IO.puts "All of them are downloaded."
  end
end

Downloader.download_packages()

该脚本首先要下载一个文本文件，其中包含要下载的包列表，这部分脚本工作正常，然后意味着继续并行下载所有包。使用我的模块时

SC

，脚本开始下载，但随后退出，我得到以下输出：

  5550K .......... .......... .......... .......... .......... 98% 11.6M 0s
  5600K .......... .......... .......... .......... .......... 99%  457K 0s
  5650K .......... .......... ..                              100%  145M=8.1s

2024-01-15 13:38:05 (702 KB/s) - ‘coreutils-9.3.tar.xz’ saved [5808696/5808696]


--2024-01-15 13:37:56--  https://github.com/systemd/systemd/archive/v254/systemd-254.tar.gz
Resolving github.com (github.com)... 140.82.121.3
Connecting to github.com (github.com)|140.82.121.3|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: https://codeload.github.com/systemd/systemd/tar.gz/refs/tags/v254 [following]
--2024-01-15 13:37:56--  https://codeload.github.com/systemd/systemd/tar.gz/refs/tags/v254
Resolving codeload.github.com (codeload.github.com)... 140.82.121.10
Connecting to codeload.github.com (codeload.github.com)|140.82.121.10|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [application/x-gzip]
Saving to: ‘systemd-254.tar.gz’

     0K .......... .......... .......... .......... ..........  267K
    50K .......... .......... .......... .......... .......... 27.2M
   100K .......... .......... .......... .......... ..........  442K
   150K .......... .......... .......... .......... ..........  202K
[many similar lines]
8.10M 0s
  6200K .......... .......... .......... .......... .......... 97% 31.7M 0s
  6250K .......... .......... .......... .......... .......... 98% 1.48M 0s
  6300K .......... .......... .......... .......... .......... 98%  700K 0s
  6350K .......... .......... .......... .......... .......... 99% 5.73M 0s
  6400K .......... .......... .......                         100%  460M=10s

2024-01-15 13:38:07 (639 KB/s) - ‘grub-2.06.tar.xz’ saved [6581924/6581924]


** (exit) exited in: Task.await(%Task{mfa: {:erlang, :apply, 2}, owner: #PID<0.96.0>, pid: #PID<0.110.0>, ref: #Reference<0.1214714622.3043557380.75212>}, 5000)
    ** (EXIT) time out
    (elixir 1.14.0) lib/task.ex:830: Task.await/2
    (elixir 1.14.0) lib/enum.ex:975: Enum."-each/2-lists^foreach/1-0-"/2
    wget.exs:28: Downloader.download_packages/0

而如果我使用 Elixir 的

System module the script does its job and prints 

“所有这些都已下载。”` 到屏幕上。

Answer 1

返回的错误是：

exited in: Task.await(..., 5000)
** (EXIT) time out

Task.await

的默认超时为 5 秒。大概下载一堆文件需要更长的时间。

将超时增加到适合您的用例的合理值，或者如果您不想超时，则

:infinity

。

|> Enum.each(&Task.await(&1, :infinity)