为什么FileSystemWatcher在Linux容器中无法监视Windows卷 [英] Why FileSystemWatcher doesn't work in Linux container watching Windows volume

问题描述

给出程序:

 使用系统；使用System.IO;命名空间fsw_bug_poc{班级计划{私有静态FileSystemWatcher _fileSystemWatcher;静态void Main(string [] args){_fileSystemWatcher = new FileSystemWatcher("Watched"，"*.*");_fileSystemWatcher.Changed + =通知；_fileSystemWatcher.Created + =通知；_fileSystemWatcher.Deleted + =通知；_fileSystemWatcher.Renamed + =通知;_fileSystemWatcher.IncludeSubdirectories = true;_fileSystemWatcher.EnableRaisingEvents = true;Console.ReadKey(false);}私有静态无效通知(对象发送者，FileSystemEventArgs e){Console.WriteLine($"{e.FullPath} {e.ChangeType}");}}} 

Dockerfile:

  FROM mcr.microsoft.com/dotnet/core/runtime:2.2-stretch-slim AS基础WORKDIR/app从mcr.microsoft.com/dotnet/core/sdk:2.2-stretch AS构建WORKDIR/srcCOPY ["fsw-bug-poc.csproj"，"]运行dotnet还原"fsw-bug-poc.csproj"复制 ..WORKDIR"/src/"RUN dotnet构建"fsw-bug-poc.csproj" -c版本-o/app从构建AS发布RUN dotnet发布"fsw-bug-poc.csproj" -c版本-o/app从基础AS决赛WORKDIR/appCOPY --from =发布/app.ENV DOTNET_USE_POLLING_FILE_WATCHER = true运行mkdir -p/app/观看音量/app/已观看ENTRYPOINT ["dotnet"，"fsw-bug-poc.dll"] 

根据

修改共享卷文件夹中的文件:

什么都没发生！

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

解决方案

切换到 PhysicalFileProvider .Watch完成了这项工作.对于文件系统监视策略，这似乎是一种更可移植的实现.

PhysicalFileProvider 的当前实现支持 DOTNET_USE_POLLING_FILE_WATCHER 环境变量.我在 FileSystemWatcher 实现中找不到任何引用.

 使用系统；使用System.IO;命名空间fsw_bug_poc{班级计划{私有静态PhysicalFileProvider _fileProvider;静态void Main(string [] args){_fileProvider =新的PhysicalFileProvider(Path.Combine(Directory.GetCurrentDirectory()，已监视")));WatchForFileChanges();Console.ReadKey(false);}私人无效WatchForFileChanges(){_fileChangeToken = _fileProvider.Watch("*.*");_fileChangeToken.RegisterChangeCallback(Notify，默认);}私有无效通知(对象状态){Console.WriteLine(检测到文件更改")；WatchForFileChanges();}}} 

Given the program:

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}");
        }
    }
}

The 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"]

According to this link adding ENV DOTNET_USE_POLLING_FILE_WATCHER=true to the Dockerfile fixes the FileSystemWatcher not working inside the container.

Even with this fix, FileSystemWatcher will not work when running a Linux container on Windows and mounting a shared driver to a volume:

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

Modifying a file inside the container:

Modifying files in the shared volume folder:

Nothing happens!!

Can someone explain what is going on? The FileSystemWatcher is using a polling strategy, so it should work the same way, shouldn't it?

解决方案

Switching to PhysicalFileProvider.Watch did the job. It seems to be a more portable implementation for file system watching strategies.

The current implementation of PhysicalFileProvider supports the DOTNET_USE_POLLING_FILE_WATCHER environment variable. I couldn't find any reference of it in FileSystemWatcher implementation.

using System;
using System.IO;

namespace fsw_bug_poc
{
    class Program
    {
        private static PhysicalFileProvider _fileProvider;

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

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

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

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