Asp.Net Core使用System.Drawing.Common部署到docker报错问题
Asp.Net Core 2.1发布后，正式支持System.Drawing.Common绘图了，可以用来做一些图片验证码之类的功能。但是把网站部署到docker容器里运行会遇到很多问题，也是非常闹心的，本文记录这些问题，希望帮到有需要的人。
创建网站
前提条件：安装最新版VS2017和Net Core SDK 2.1。
首先新建网站，选择Asp.Net Core 2.1 Web应用程序（模型视图控制器），不勾选docker，我习惯自行编写Dockerfile。
指定网站访问端口5000。
public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
WebHost.CreateDefaultBuilder(args)
//必须指定端口，否则在Win10命令行运行端口是5000，在CentOS docker运行端口是80
.UseUrls("http://*:5000")
.UseStartup<Startup>();
为了调试方便，把隐私要求和https要求先屏蔽。
public void ConfigureServices(IServiceCollection services)
{
services.Configure<CookiePolicyOptions>(options =>
{
// This lambda determines whether user consent for non-essential cookies is needed for a given request.
//options.CheckConsentNeeded = context => true;
options.MinimumSameSitePolicy = SameSiteMode.None;
});
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Home/Error");
//app.UseHsts();
}
//app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});
}
修改appsettings.json输出全部调试信息，便于查找错误。
{
"Logging": {
"LogLevel": {
"Default": "Debug"
}
},
"AllowedHosts": "*"
}
调试运行一下，确认网站没问题。
把Home控制器的Index页面改一下，简单粗暴一点，就显示一个图片好了。
@{
ViewData["Title"] = "Home Page";
}
<h4>System.Drawing.Common绘图</h4>
<img src="Home/GetImg" alt="pic" class="img-thumbnail" width="400" height="200" />
NuGet安装System.Drawing.Common。
给Home控制器增加一个绘图函数GetImg。
public IActionResult GetImg()
{
_logger.LogInformation($"{DateTime.Now:yyyy-MM-dd HH:mm:ss:fff}, start create image");
string msg = $"{DateTime.Now:HH:mm:ss}, 您好 drawing from .NET Core";
Image image = new Bitmap(400, 200);
Graphics graph = Graphics.FromImage(image);
graph.Clear(Color.Azure);
Pen pen = new Pen(Brushes.Black);
graph.DrawLines(pen, new Point[] { new Point(10, 10), new Point(380, 180) });
graph.DrawString(msg, new Font(new FontFamily("微软雅黑"), 12, FontStyle.Bold), Brushes.Blue, new PointF(10, 90));
//把图片保存到内存文件流
MemoryStream ms = new MemoryStream();
image.Save(ms, ImageFormat.Png); ;
byte[] buf = ms.GetBuffer();
_logger.LogInformation($"{DateTime.Now:yyyy-MM-dd HH:mm:ss:fff}, finish create image");
return File(buf, "image/png");
}
调试运行一下，是没问题的。
部署网站到docker
编写Dockerfile，注意把文件属性“复制到输出目录”设置为“如果较新则复制”。
FROM microsoft/dotnet:2.1-aspnetcore-runtime WORKDIR /app COPY . /app EXPOSE 5000 ENTRYPOINT ["dotnet", "NetCoreDraw.dll"]
重新编译网站，以文件夹方式发布到默认的bin\Release\PublishOutput。在Windows控制台进入发布目录，输入dotnet NetCoreDraw.dll运行网站，浏览器访问http://localhost:5000/，确认没问题。
编写docker-compose.yml
version: '3'
services:
myweb:
container_name: myweb
image: mywebimage
build:
context: ./PublishOutput
dockerfile: Dockerfile
ports:
- "5000:5000"
environment:
- ASPNETCORE_ENVIRONMENT=Production
- TZ=Asia/Shanghai
restart: always
我用CentOS 7.3虚拟机做试验，安装好docker环境，用Xshell访问虚拟机，用Xftp把PublishOutput文件夹、docker-compose.yml拖到Home下面。
进入Home目录，把容器跑起来。
[root@localhost home]# docker-compose up
Creating network "home_default" with the default driver
Building myweb
Step 1/5 : FROM microsoft/dotnet:2.1-aspnetcore-runtime
2.1-aspnetcore-runtime: Pulling from microsoft/dotnet
be8881be8156: Pull complete
f854db899319: Pull complete
4591fd524b8e: Pull complete
65f224da8749: Pull complete
Digest: sha256:a43b729b84f918615d4cdce92a8bf59e3e4fb2773b8491a7cf4a0d728886eeba
Status: Downloaded newer image for microsoft/dotnet:2.1-aspnetcore-runtime
---> fcc3887985bb
Step 2/5 : WORKDIR /app
Removing intermediate container aba36715acfc
---> 25bc5bb6871f
Step 3/5 : COPY . /app
---> 9baaa790a82f
Step 4/5 : EXPOSE 5000
---> Running in 269408c67989
Removing intermediate container 269408c67989
---> fbd444c44d20
Step 5/5 : ENTRYPOINT ["dotnet", "NetCoreDraw.dll"]
---> Running in 2a9ba559b137
Removing intermediate container 2a9ba559b137
---> b1bb1dccd49a
Successfully built b1bb1dccd49a
Successfully tagged mywebimage:latest
WARNING: Image for service myweb was built because it did not already exist. To rebuild this image you must use `docker-compose build` or `docker-compose up --build`.
Creating myweb ... done
Attaching to myweb
myweb | warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
myweb | No XML encryptor configured. Key {1f87d27e-c6b1-435f-bab6-aebacd6d6817} may be persisted to storage in unencrypted form.
myweb | Hosting environment: Production
myweb | Content root path: /app
myweb | Now listening on: http://[::]:5000
myweb | Application started. Press Ctrl+C to shut down.
在浏览器访问我的虚拟机里的网站http://192.168.41.129:5000/，图片显示不出来。
在Xshell可以看到容器调试信息，发生了错误。
myweb | 2018-07-29 09:50:04:753, start create image myweb | info: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2] myweb | Executed action NetCoreDraw.Controllers.HomeController.GetImg (NetCoreDraw) in 18.5988ms myweb | fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1] myweb | An unhandled exception has occurred while executing the request. myweb | System.TypeInitializationException: The type initializer for 'Gdip' threw an exception. ---> System.DllNotFoundException: Unable to load shared library 'libdl' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: liblibdl: cannot open shared object file: No such file or directory myweb | at Interop.Libdl.dlopen(String fileName, Int32 flag) myweb | at System.Drawing.SafeNativeMethods.Gdip.LoadNativeLibrary() myweb | at System.Drawing.SafeNativeMethods.Gdip..cctor() myweb | --- End of inner exception stack trace ---
找不到库文件libdl，网上有类似的问题和解决方案，就是建立一个文件连接。
https://q.cnblogs.com/q/107946/
但是aspnetcore容器中的库文件位置，跟正式发行版本的CentOS和Ubuntu不太一样，得进入容器去找。在容器运行的时候，通过Xshell的复制功能，再开一个终端窗口，进入容器。
docker exec -it myweb /bin/bash
aspnetcore容器不支持locate命令，我对Linux系统文件位置不熟，只好硬着头皮挨个看了一遍，还好目录不多，最后确定在这里。
root@544f7be29f68:/# ls lib/x86_64-linux-gnu/libdl*
lib/x86_64-linux-gnu/libdl-2.24.so lib/x86_64-linux-gnu/libdl.so.2
所以修改Dockerfile为
FROM microsoft/dotnet:2.1-aspnetcore-runtime RUN ln -s /lib/x86_64-linux-gnu/libdl-2.24.so /lib/x86_64-linux-gnu/libdl.so WORKDIR /app COPY . /app EXPOSE 5000 ENTRYPOINT ["dotnet", "NetCoreDraw.dll"]
重新编译、发布网站到虚拟机，重新运行编译运行容器。
[root@localhost home]# docker-compose up --build
浏览网站，仍然无法显示图片，但是错误内容变了。
myweb | fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1] myweb | An unhandled exception has occurred while executing the request. myweb | System.TypeInitializationException: The type initializer for 'Gdip' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'libgdiplus': The specified module could not be found. myweb | at System.Runtime.InteropServices.FunctionWrapper`1.get_Delegate() myweb | at System.Drawing.SafeNativeMethods.Gdip.GdiplusStartup(IntPtr& token, StartupInput& input, StartupOutput& output) myweb | at System.Drawing.SafeNativeMethods.Gdip..cctor() myweb | --- End of inner exception stack trace ---
这次是找不到libgdiplus，网上也有关于这个问题的解决方案。
https://q.cnblogs.com/q/103863/
因为需要在容器跑起来的时候安装一些东西，所以要更换为国内的源，提高速度。参考
https://www.cnblogs.com/OMango/p/8519980.html
把Dockerfile改为这样了，注意更新源之后要apt-get update一下，否则会报错Unable to locate package libgdiplus。
FROM microsoft/dotnet:2.1-aspnetcore-runtime RUN ln -s /lib/x86_64-linux-gnu/libdl-2.24.so /lib/x86_64-linux-gnu/libdl.so RUN echo "deb http://mirrors.aliyun.com/debian wheezy main contrib non-free \ deb-src http://mirrors.aliyun.com/debian wheezy main contrib non-free \ deb http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \ deb-src http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \ deb http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free \ deb-src http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free" > /etc/apt/sources.list RUN apt-get update RUN apt-get install libgdiplus -y && ln -s libgdiplus.so gdiplus.dll WORKDIR /app COPY . /app EXPOSE 5000 ENTRYPOINT ["dotnet", "NetCoreDraw.dll"]
再次运行，终于看到图片了，但是汉字没有显示出来。
参考上面的文章，把字体文件复制到容器中，再安装字体相关的功能即可。最终Dockerfile长这样。
FROM microsoft/dotnet:2.1-aspnetcore-runtime RUN ln -s /lib/x86_64-linux-gnu/libdl-2.24.so /lib/x86_64-linux-gnu/libdl.so RUN echo "deb http://mirrors.aliyun.com/debian wheezy main contrib non-free \ deb-src http://mirrors.aliyun.com/debian wheezy main contrib non-free \ deb http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \ deb-src http://mirrors.aliyun.com/debian wheezy-updates main contrib non-free \ deb http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free \ deb-src http://mirrors.aliyun.com/debian-security wheezy/updates main contrib non-free" > /etc/apt/sources.list RUN apt-get update RUN apt-get install libfontconfig1 -y RUN apt-get install libgdiplus -y && ln -s libgdiplus.so gdiplus.dll COPY ./fonts/msyh.ttc /usr/share/fonts/dejavu WORKDIR /app COPY . /app EXPOSE 5000 ENTRYPOINT ["dotnet", "NetCoreDraw.dll"]
把Win10的微软雅黑字体文件msyh.ttc放到项目的fonts目录下，设置文件属性“复制到输出目录”设置为“如果较新则复制”。
再次运行容器，搞定了。
Asp.Net Core网站跨平台部署到Linux容器运行是一个飞跃性的技术进步，但是时不时会碰到一些跟Linux系统相关的问题，总感觉是又爱又恨，心太累。
源代码
https://github.com/woodsun2018/NetCoreDraw
