Why is http.FileServer Serving Stale Content When Using Virtual Box Shared Folders?

Caching Woes with http.FileServer

The http.FileServer in the Go standard library has been known to exhibit caching issues, leading to stale content being served after file edits. A user encountered this problem and sought assistance.

Issue Description:

An application using http.FileServer was experiencing incorrect file content delivery, despite a changing Content-Length header. The content would only update after a server or system reboot.

Extended Investigation:

To rule out potential sources of caching, the user examined the application's code, but found no evidence of caching mechanisms. They also tested the application on different platforms (Windows, Ubuntu, OS X), with no change in behavior.

Solution: Avoid Virtual Box Shared Folders

After some investigation, the user discovered the culprit: Virtual Box shared folders. When files were served from a Virtual Box shared folder, the caching issue occurred. However, when the files were stored on the host system and served from there, the problem disappeared.

Cause:

The underlying issue is that Virtual Box shared folders appear to implement their own caching mechanism, which conflicts with the caching performed by http.FileServer. This leads to the stale content being served.

Recommendation:

To avoid this caching issue, it is recommended to store files intended for use in http.FileServer outside of Virtual Box shared folders. This ensures that the application's caching mechanism is the sole controller of content delivery, preventing stale content from being served.

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