Edit notifications don't work when running inside of Docker container on Windows

[matt-github-acct]

I'm running Windows 10 Enterprise, 10.0.17134

My goal is to launch a docker container, mount a volume inside the container, edit files in the volume from my host operating system and have the docker container recognize the change events. Pretty much this: https://www.zachjohnsondev.com/posts/go-docker-hot-reload-example/

Steps to reproduce

1. Create main.go file and add the following:

package main

import (
	"log"

	"github.com/fsnotify/fsnotify"
)

func main() {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		log.Fatal(err)
	}
	defer watcher.Close()

	done := make(chan bool)
	go func() {
		for {
			select {
			case event, ok := <-watcher.Events:
				if !ok {
					return
				}
				log.Println("event:", event)
				if event.Op&fsnotify.Write == fsnotify.Write {
					log.Println("modified file:", event.Name)
				}
			case err, ok := <-watcher.Errors:
				if !ok {
					return
				}
				log.Println("error:", err)
			}
		}
	}()

	err = watcher.Add(".")
	if err != nil {
		log.Fatal(err)
	}
	<-done
}

1. Create a docker-compose file and add the following:

version: "3.6"

services:
  bar:
    container_name: bar
    build: .
    ports:
      - "8080:8080"
    volumes:
      - ./:/go/src/bar

1. Create a Dockerfile file and add the following:

FROM golang:latest

WORKDIR /go/src/bar

COPY . .

RUN ["go", "get", "github.com/fsnotify/fsnotify"]

ENTRYPOINT go run main.go

1. Run docker-compose build in the directory where you've created the files.
2. Run docker-compose up in the directory where you've created the files.
3. From your host operating system, add a comment to main.go and notice that no edit events are reported.
4. Run docker exec -it bar bash to connect to the docker container. Edit main.go from the container shell to confirm that edit events are being reported when the edit is performed within the container.

[nathany]

I'm not sure how Docker for Windows is mounting the shared folder, but generally file shares such as NFS don't support notifications.

A polling fallback (#9) is the only solution I know of when the underlying system doesn't provide events.

For now we should document the limitation, but first we should confirm on other operating systems. It may work on Linux, depending on how the Docker container is mounted there.

[oxycoder]

Currently it work perfectly fine with folder mount to docker on MacOS.

[julienkosinski]

I can confirm it works well under on Docker with Linux host (Manjaro distro).

[jnach]

I can confirm it works well under on Docker with Linux host (Manjaro distro).

Which storage driver do you happen to be using? With @nathany's comment in mind, this could be filesystem dependent. In both 'working' cases, this sounds like a bind mount, not a K8's storage driver under the PVC subsystem

[jnach]

This seems to do a good job of explaining the phenomenon here..

[jnach]

Same problem, any solutions?

Sorta, see above. TL&DR This is a file-system compatibility issue. There are a few scenarios where it works when using the same underlying host filesystem, but pretty much never if there is any translation.

[arp242]

Closed as duplicate of #9; if the underlying OS mechanism doesn't work then there's not much we can do about it other than implement a polling fallback.