为什么 FileSystemWatcher 在监视 Windows 卷的 Linux 容器中不起作用

Question

鉴于程序：

using System;
using System.IO;

namespace fsw_bug_poc
{
    class Program
    {
        private static FileSystemWatcher _fileSystemWatcher;

        static void Main(string[] args)
        {
            _fileSystemWatcher = new FileSystemWatcher("Watched", "*.*");
            _fileSystemWatcher.Changed += Notify;
            _fileSystemWatcher.Created += Notify;
            _fileSystemWatcher.Deleted += Notify;
            _fileSystemWatcher.Renamed += Notify;
            _fileSystemWatcher.IncludeSubdirectories = true;
            _fileSystemWatcher.EnableRaisingEvents = true;

            Console.ReadKey(false);
        }

        private static void Notify(object sender, FileSystemEventArgs e)
        {
            Console.WriteLine($"{e.FullPath} {e.ChangeType}");
        }
    }
}

Dockerfile：

FROM mcr.microsoft.com/dotnet/core/runtime:2.2-stretch-slim AS base
WORKDIR /app

FROM mcr.microsoft.com/dotnet/core/sdk:2.2-stretch AS build
WORKDIR /src
COPY ["fsw-bug-poc.csproj", ""]
RUN dotnet restore "fsw-bug-poc.csproj"
COPY . .
WORKDIR "/src/"
RUN dotnet build "fsw-bug-poc.csproj" -c Release -o /app

FROM build AS publish
RUN dotnet publish "fsw-bug-poc.csproj" -c Release -o /app

FROM base AS final
WORKDIR /app
COPY --from=publish /app .
ENV DOTNET_USE_POLLING_FILE_WATCHER=true
RUN mkdir -p /app/Watched
VOLUME /app/Watched
ENTRYPOINT ["dotnet", "fsw-bug-poc.dll"]

根据这个链接添加ENV DOTNET_USE_POLLING_FILE_WATCHER=true到 Dockerfile 修复了 FileSystemWatcher 在容器内不起作用。

即使有了这个修复，FileSystemWatcher 在 Windows 上运行 Linux 容器并将共享驱动程序安装到卷时也不会工作：

docker build -t fsw-bug-poc .
docker run -it --rm -v C:\Shared:/app/Watched fsw-bug-poc

修改容器内的文件：

修改共享卷文件夹中的文件：

没发生什么事！！

有人可以解释发生了什么吗？FileSystemWatcher 正在使用轮询策略，所以它应该以相同的方式工作，不是吗？

Answer 1

切换到PhysicalFileProvider .Watch 完成了这项工作。对于文件系统监视策略来说，它似乎是一种更便携的实现。

当前的实现PhysicalFileProvider支持DOTNET_USE_POLLING_FILE_WATCHER环境变量。我在FileSystemWatcher实现中找不到它的任何参考。

using Microsoft.Extensions.FileProviders;
using Microsoft.Extensions.Primitives;
using System;
using System.IO;

namespace fsw_bug_poc
{
    class Program
    {
        private static PhysicalFileProvider _fileProvider;
        private static IChangeToken _fileChangeToken;

        static void Main(string[] args)
        {
            _fileProvider = new PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory(), "."));
            WatchForFileChanges();

            Console.ReadKey(false);
        }

        private static void WatchForFileChanges()
        {
            _fileChangeToken = _fileProvider.Watch("*.*");
            _fileChangeToken.RegisterChangeCallback(Notify, default);
        }

        private static void Notify(object state)
        {
            Console.WriteLine("File change detected");
            WatchForFileChanges();
        }
    }
}