无法在 docker 中使用 libgdiplus

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概述

近期 @sheng-jie 为 WTM 框架提了个 issue #50 The captcha doesn’t show if deploy the app to the docker，并给出了解决方案及建议。

在此先感谢一下 @sheng-jie的贡献。

解决方案

默认镜像

这个问题主要是在于默认的 docker 镜像 mcr.microsoft.com/dotnet/core/aspnet:2.2 不包含 libgdiplus 的依赖。

在容器运行之后，调用了相关的 API 就将触发以下异常：

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fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
      An unhandled exception has occurred while executing the request.
System.TypeInitializationException: The type initializer for 'Gdip' threw an exception. ---> System.DllNotFoundException: Unable to load DLL 'libgdiplus': The specified module could not be found.
   at System.Runtime.InteropServices.FunctionWrapper`1.get_Delegate()
   at System.Drawing.SafeNativeMethods.Gdip.GdiplusStartup(IntPtr& token, StartupInput& input, StartupOutput& output)
   at System.Drawing.SafeNativeMethods.Gdip..cctor()
   --- End of inner exception stack trace ---
   at System.Drawing.SafeNativeMethods.Gdip.GdipCreateBitmapFromScan0(Int32 width, Int32 height, Int32 stride, Int32 format, HandleRef scan0, IntPtr& bitmap)
   at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)
   at WalkingTec.Mvvm.Mvc._FrameworkController.GetVerifyCode() in /app/src/WalkingTec.Mvvm.Mvc/_FrameworkController.cs:line 775
   at lambda_method(Closure , Object , Object[] )
   at Microsoft.Extensions.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters)
   at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.Invoke(HttpContext context)

根据 @sheng-jie 提供的解决方案，只需在 Dockerfile 中添加如下配置命令即可解决。

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# install libgdiplus for System.Drawing
RUN apt-get update && \
    apt-get install -y --allow-unauthenticated libgdiplus libc6-dev

完整 Dockerfile 文件如下所示：

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FROM mcr.microsoft.com/dotnet/core/sdk:2.2 AS build
WORKDIR /app

COPY . .
RUN dotnet publish "./demo/WalkingTec.Mvvm.Demo/WalkingTec.Mvvm.Demo.csproj" -c Release -o /app/out

FROM mcr.microsoft.com/dotnet/core/aspnet:2.2 AS runtime
WORKDIR /app
COPY --from=build /app/out ./

# install libgdiplus for System.Drawing
RUN apt-get update && \
    apt-get install -y --allow-unauthenticated libgdiplus libc6-dev

ENV ASPNETCORE_URLS http://+:80
ENV ASPNETCORE_ENVIRONMENT Production
ENTRYPOINT ["dotnet", "WalkingTec.Mvvm.Demo.dll"]

alpine 镜像

但是这并未解决 mcr.microsoft.com/dotnet/core/aspnet:2.2-alpine 镜像的问题。

当然解决思路类似，在 alpine 包源上查找 libgdiplus 依赖即可。

注意：当前 alpine 下的 libgdiplus 并未正式发布，还是测试版本

下面我直接给出完整的 Dockerfile 文件内容

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FROM mcr.microsoft.com/dotnet/core/sdk:2.2-alpine AS build
WORKDIR /app

COPY . .
RUN dotnet publish "./demo/WalkingTec.Mvvm.Demo/WalkingTec.Mvvm.Demo.csproj" -c Release -o /app/out

FROM mcr.microsoft.com/dotnet/core/aspnet:2.2-alpine AS runtime
WORKDIR /app
COPY --from=build /app/out ./

# install libgdiplus for System.Drawing
RUN apk add libgdiplus --update-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ --allow-untrusted

ENV ASPNETCORE_URLS http://+:80
ENV ASPNETCORE_ENVIRONMENT Production
ENTRYPOINT ["dotnet", "WalkingTec.Mvvm.Demo.dll"]

当我以为已经解决 libgdiplus 的问题时，经测试又出现如下问题：

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fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[1]
      An unhandled exception has occurred while executing the request.
System.ArgumentException: Font '?' cannot be found.
   at System.Drawing.FontFamily.GetGdipGenericSansSerif()
   at System.Drawing.FontFamily.get_GenericSansSerif()
   at System.Drawing.Font.CreateFont(String familyName, Single emSize, FontStyle style, GraphicsUnit unit, Byte charSet, Boolean isVertical)
   at WalkingTec.Mvvm.Mvc._FrameworkController.GetVerifyCode() in /app/src/WalkingTec.Mvvm.Mvc/_FrameworkController.cs:line 795
   at lambda_method(Closure , Object , Object[] )
   at Microsoft.Extensions.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters)
   at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.SyncActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.Invoke(HttpContext context)

提示也很明确未找到字体库文件，所以解决思路是需要为 alpine 镜像安装一个字体库。

下面我直接给出完整的 Dockerfile 文件内容

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FROM mcr.microsoft.com/dotnet/core/sdk:2.2-alpine AS build
WORKDIR /app

COPY . .
RUN dotnet publish "./demo/WalkingTec.Mvvm.Demo/WalkingTec.Mvvm.Demo.csproj" -c Release -o /app/out


FROM mcr.microsoft.com/dotnet/core/aspnet:2.2-alpine AS runtime
WORKDIR /app
COPY --from=build /app/out ./

# install libgdiplus for System.Drawing
RUN apk add libgdiplus --update-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ --allow-untrusted && \
    apk add terminus-font

ENV ASPNETCORE_URLS http://+:80
ENV ASPNETCORE_ENVIRONMENT Production
ENTRYPOINT ["dotnet", "WalkingTec.Mvvm.Demo.dll"]

参考文章