On Mon, Jan 25, 2021 at 08:22:32PM +0100, Miklos Szeredi wrote: > On Fri, Jan 22, 2021 at 5:58 PM Eric Ernst <[email protected]> wrote: > > > > Hey ya'll, > > > > As highlighted nicely at [1], a common pattern in Kubernetes is to watch > > for changes to files/directories passed in as Configmaps or secrets. > > Sidecars typically use inotify to watch for changes and then signal the > > primary container or perform other changes based on the reconfiguration. > > > > In the context of Kata, these files/dirs are passed in utilizing virtio-fs. > > Since FUSE itself doesn't support inotify, this pattern will fail. I'm > > looking at ways to work-around this gap, including: > > > > 1) documenting this as a compatibility limitation ("don't do this!"). > > 2) suggesting end-users modify their sidecars and utilize poll > > 3) doing an inotify on the host, and when changes are identified, notify > > the guest agent who can then modify the files on disk to trigger an inotify > > 4) Working on contributing to libfuse in order to add inotify support. > > > > (4) is the right thing, but will take quite a bit of time before it can be > > used. I'm curious if other folks have suggestions for workarounds (I don't > > like any of the ones I suggested), and if anyone has taken a look at (4)? > > Here's a thread on enabling inotify in remote fs: > > https://lore.kernel.org/linux-fsdevel/[email protected]/ > > The discussion didn't get too far, it seems there's not a very big > interest in this, but conceptually it doesn't seem too difficult.
Vivek Goyal previously experimented with adding a notification virtqueue to the virtio-fs device so that FUSE_NOTIFY_* messages can be supported. That code can be brought back and merged. However, due to the number of flags in inotify(7) I think this is a non-trivial project. Whoever wants to tackle this feature should be aware that it may take a few months (3?) to fully implement and test. Stefan
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