利用C＃编写Linux守护进程实例代码

前言

Linux守护进程是Linux的后台服务进程，相当于Windows服务，对于为Linux开发服务程序的朋友来说，Linux守护进程相关技术是必不可少的，因为这个技术不仅仅是为了开发守护进程，还可以拓展到多进程，父子进程文件描述符共享，父子进程通讯、控制等方面，是实现Linux大型服务的基础技术之一。

如果要在Red Hat Enterprise Linux上将.NET Core进程作为后台进程运行，则可以创建自定义systemd单元。今天我将为.NET Core编写两个自定义系统单元的例子。一个是运行.NET Core控制台应用程序的一种类型，另一个是运行ASP.NET Core Web应用程序的简单类型。

控制台应用程序

建立一个应用程序

您可以用dotnet run在systemd中使用指定项目目录作为工作目录。但是，我们来构建一个二进制文件并将其用于systemd。用dotnet new 命令创建您的项目后编辑Program.cs如下。

using System;
using System.IO;
namespace ConsoleApplication
{
 public class Program
 {
  public static void Main(string[] args)
  {
   var path = Path.GetTempFileName();
   File.WriteAllText(path, "Hello Temp File!");
   Console.WriteLine($"Wrote temp file: {path}");
  }
 }
}

然后用dotnet publish命令发布项目。你会看到bin/<Configuration>/<Framework>目录下的二进制文件。

$ dotnet publish -c Release
Publishing ConsoleApp for .NETCoreApp,Version=v1.1
Project ConsoleApp (.NETCoreApp,Version=v1.1) was previously compiled. Skipping compilation.
publish: Published to /home/tatanaka/Documents/git/tanaka-takayoshi/SystemdExample/1.1/ConsoleApp/bin/Release/netcoreapp1.1/publish
Published 1/1 projects successfully

创建一个自定义的systemd

首先，创建一个运行守护进程和工作目录的用户。

$ sudo useradd -s /sbin/nologin dotnetuser
$ sudo mkdir /var/SystemdExample
$ sudo cp /home/tatanaka/Documents/git/tanaka-takayoshi/SystemdExample/1.1/ConsoleApp/bin/Release/netcoreapp1.1/publish/* /var/SystemdExample
$ sudo chown -R dotnetuser:dotnetuser /var/SystemdExample

然后在/etc/systemd/system/目录下创建一个自定义的systemd单元文件。文件名应该是<unit-name>.<unit-type>。我创建的目录和文件名为：/etc/systemd/system/netcore-console-example.service。

[Unit]
Description=Example for .NET Core ConsoleApp with systemd
DefaultDependencies=no

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/opt/rh/rh-dotnetcore11/root/usr/bin/dotnet ConsoleApp.dll
WorkingDirectory=/var/SystemdExample
User=dotnetuser
Group=dotnetuser

[install]

您应该在ExecStart中指定dotnet的完整路径。以上是红帽提供的.NET Core 1.1的情况。然后你可以用systemctl命令执行守护进程。您可以使用systemctl status命令或journalctl命令查看控制台输出。

$ sudo systemctl start netcore-console-example.service
$ sudo systemctl status netcore-console-example.service
● netcore-console-example.service - Example for .NET Core ConsoleApp with systemd
 Loaded: loaded (/etc/systemd/system/netcore-console-example.service; enabled; vendor preset: disabled)
 Active: inactive (dead) since Fri 2017-02-24 00:29:16 JST; 13s ago
 Process: 18075 ExecStart=/opt/rh/rh-dotnetcore11/root/usr/bin/dotnet ConsoleApp.dll (code=exited, status=0/SUCCESS)
 Main PID: 18075 (code=exited, status=0/SUCCESS)

Feb 24 00:29:16 localhost.localdomain systemd[1]: Starting Example for .NET Core ConsoleApp with systemd...
Feb 24 00:29:16 localhost.localdomain dotnet[18075]: Wrote temp file: /tmp/tmph1ok6H.tmp
Feb 24 00:29:16 localhost.localdomain systemd[1]: Started Example for .NET Core ConsoleApp with systemd.

$ journalctl -u netcore-console-example.service -e
Feb 24 00:29:16 localhost.localdomain systemd[1]: Starting Example for .NET Core ConsoleApp with systemd...
Feb 24 00:29:16 localhost.localdomain dotnet[18075]: Wrote temp file: /tmp/tmph1ok6H.tmp
Feb 24 00:29:16 localhost.localdomain systemd[1]: Started Example for .NET Core ConsoleApp with systemd.
$ sudo cat /tmp/tmph1ok6H.tmp
Hello Temp File!

使用PrivateTemp

在上述系统单元中，程序在临时文件夹下写入一个文件。你有时想写一个来自其他用户的临时文件是安全的。您可以在[Service]section中的指定使用PrivateTemp。

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/opt/rh/rh-dotnetcore11/root/usr/bin/dotnet ConsoleApp.dll
WorkingDirectory=/var/SystemdExample
User=dotnetuser
Group=dotnetuser
PrivateTemp=true

重新加载单元文件后，程序可以像前一样访问/tmp目录，但这不是实际的/tmp目录。

$ sudo systemctl daemon-reload
$ sudo systemctl start netcore-console-example.service
$ sudo systemctl status netcore-console-example.service
● netcore-console-example.service - Example for .NET Core ConsoleApp with systemd
 Loaded: loaded (/etc/systemd/system/netcore-console-example.service; enabled; vendor preset: disabled)
 Active: inactive (dead) since Fri 2017-02-24 00:35:46 JST; 12s ago
 Process: 18415 ExecStart=/opt/rh/rh-dotnetcore11/root/usr/bin/dotnet ConsoleApp.dll (code=exited, status=0/SUCCESS)
 Main PID: 18415 (code=exited, status=0/SUCCESS)

Feb 24 00:35:46 localhost.localdomain systemd[1]: Starting Example for .NET Core ConsoleApp with systemd...
Feb 24 00:35:46 localhost.localdomain dotnet[18415]: Wrote temp file: /tmp/tmpJLWAGC.tmp
Feb 24 00:35:46 localhost.localdomain systemd[1]: Started Example for .NET Core ConsoleApp with systemd.
$ ls /tmp/tmpJLWAGC.tmp
ls: cannot access /tmp/tmpJLWAGC.tmp: No such file or directory

Web应用程序

建立一个应用程序

现在我们来构建一个ASP.NET Core Web应用程序。今天我使用默认的模板项目。

$ dotnet new -t web
Created new C# project in /home/tatanaka/Documents/git/tanaka-takayoshi/SystemdExample/1.1/WebApp.
$ dotnet restore
** snipped**
log : Restore completed in 9721ms.
$ dotnet publish -c Release
Publishing WebApp for .NETCoreApp,Version=v1.1
** snipped **
publish: Published to /home/tatanaka/Documents/git/tanaka-takayoshi/SystemdExample/1.1/WebApp/bin/Release/netcoreapp1.1/publish
Published 1/1 projects successfully

现在可以用dotnet命令运行。

$ dotnet bin/Release/netcoreapp1.1/publish/WebApp.dll
info: Microsoft.Extensions.DependencyInjection.DataProtectionServices[0]
  User profile is available. Using '/home/tatanaka/.aspnet/DataProtection-Keys' as key repository; keys will not be encrypted at rest.
Hosting environment: Production
Content root path: /home/tatanaka/Documents/git/tanaka-takayoshi/SystemdExample/1.1/WebApp
Now listening on: http://localhost:5000
Application started. Press Ctrl+C to shut down.

创建一个自定义的systemd

为这个Web应用程序也指定dotnetuser名称。

$ sudo mkdir /var/SystemdExample
$ sudo cp -R bin/Release/netcoreapp1.1/publish/* /var/SystemdWebExample
$ sudo chown -R dotnetuser:dotnetuser /var/SystemdWebExample

然后创建一个自定义的systemd单元文件/etc/systemd/system/netcore-web-example.service。

[Unit]
Description=Example for .NET Core WebApp with systemd
DefaultDependencies=no
Wants=network.target # network is required
After=network.target

[Service]
ExecStart=/opt/rh/rh-dotnetcore11/root/usr/bin/dotnet WebApp.dll
WorkingDirectory=/var/SystemdWebExample
Restart=always
RestartSec=10 # Restart service after 10 seconds if dotnet service crashes
SyslogIdentifier=dotnet-example
User=dotnetuser
Group=dotnetuser
PrivateTmp=true
Environment=ASPNETCORE_ENVIRONMENT=Production # specify environment variable for environment
Environment=ASPNETCORE_URLS=http://*:8080 # specify environement variable for listening port

[Install]
WantedBy = multi-user.target

最后，您可以将ASP.NET Core应用程序作为Linux守护程序运行。请注意，此应用程序侦听端口8080代替了ASP.NET Core 默认的 5000，因为我在ASPNETCORE_URLS单元文件中指定了环境变量  。

$ systemctl start netcore-web-example.service
[tatanaka@localhost WebApp]$ systemc^C
[tatanaka@localhost WebApp]$ sudo systemctl status netcore-web-example.service
[sudo] password for tatanaka:
● netcore-web-example.service - Example for .NET Core WebApp with systemd
 Loaded: loaded (/etc/systemd/system/netcore-web-example.service; disabled; vendor preset: disabled)
 Active: active (running) since Sat 2017-02-25 01:02:12 JST; 11s ago
 Main PID: 7041 (dotnet)
 CGroup: /system.slice/netcore-web-example.service
   └─7041 /opt/rh/rh-dotnetcore11/root/usr/bin/dotnet WebApp.dll

Feb 25 01:02:12 localhost.localdomain systemd[1]: Started Example for .NET Core WebApp with systemd.
Feb 25 01:02:12 localhost.localdomain systemd[1]: Starting Example for .NET Core WebApp with systemd...
Feb 25 01:02:12 localhost.localdomain dotnet-example[7041]: info: Microsoft.Extensions.DependencyInjection.DataProtectionServices[0]
Feb 25 01:02:12 localhost.localdomain dotnet-example[7041]: User profile is available. Using '/home/dotnetuser/.aspnet/DataProtection-Keys' as key repository; keys will not be encrypted at rest.
Feb 25 01:02:13 localhost.localdomain dotnet-example[7041]: Hosting environment: Production
Feb 25 01:02:13 localhost.localdomain dotnet-example[7041]: Content root path: /var/SystemdWebExample
Feb 25 01:02:13 localhost.localdomain dotnet-example[7041]: Now listening on: http://*:8080
Feb 25 01:02:13 localhost.localdomain dotnet-example[7041]: Application started. Press Ctrl+C to shut down.

$ journalctl -u netcore-web-example -xf
-- Logs begin at Mon 2017-02-20 11:58:31 JST. --
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: info: Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware[2]
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: Sending file. Request path: '/images/banner4.svg'. Physical path: '/var/SystemdWebExample/wwwroot/images/banner4.svg'
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: Request finished in 0.1973ms 200 image/svg+xml
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: info: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: Request starting HTTP/1.1 GET http://localhost:8080/favicon.ico
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: info: Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware[2]
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: Sending file. Request path: '/favicon.ico'. Physical path: '/var/SystemdWebExample/wwwroot/favicon.ico'
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: info: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
Feb 25 01:02:36 localhost.localdomain dotnet-example[7041]: Request finished in 0.5824ms 200 image/x-icon

然而这对于ASP.NET Core的生产使用来说是不够的。你可能需要设置一个反向代理服务器，比如Jexus,nginx，防火墙等等。

Writing a Linux daemon in C#

总结

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