1

I have set up a mount point using the s3fs FUSE filesystem and autofs to talk to an Amazon S3 bucket, but it is excruciatingly slow to edit a file in the bucket in emacs - it is basically unusable due to the delays after every keypress, which cause emacs to hang completely until it finishes its I/O.

What can I do to avoid this problem?

1

This appears to have been due to this issue in projectile, which I use.

I followed the suggestion in a comment on that issue of using this workaround:

(add-hook 'find-file-hook
          (lambda ()
            (if (locate-dominating-file default-directory ".git")
                (projectile-mode))))

i.e. removing

(global-projectile-mode)

from my .emacs and replacing it with the above code, and performance is now acceptable (there is a lag on opening the file, and on the first keypress that makes an edit to the file, as I would expect). This does mean that projectile is only activated in git projects, but that's fine for me - and the same workaround can easily be extended to other version control systems if necessary.

0

I initially used this simple Linux script to copy the file to a fast filesystem and then copy it back again (see my other answer for what I am now doing). Only the line beginning with TMP= should need to be changed for other operating systems. The only slight complexity is dealing with simultaneous edits to identically-named files in different S3 buckets (without replacing the filename with randomly-generated garbage, which would be the easy way out).

#! /bin/bash -peux
# Edit files from slow filesystems in emacs
TMP=/run/user/$(id -u)
dest=$TMP/"$(basename "$1")"
src_dir="$(dirname "$1")"
prefix=""
while [ -e "$dest" ]; do
    prefix="$(basename "$src_dir")/$prefix"
    src_dir="$(dirname "$src_dir")"
    if [ "$src_dir" = "/" ]; then
        echo Unable to generate unique filename >&2
        exit 2
    fi
    mkdir $TMP/"$prefix" || :
    dest=$TMP/"$prefix$(basename "$1")"
done
cp -p "$1" $dest || :
emacsclient "$dest"
cp -pu "$dest" "$1"
rm "$dest"
  • Can tramp deal with this? – phils Feb 23 '16 at 23:54
  • Doesn't look like it - s3 uses a proprietary protocol. – Robin Green Feb 24 '16 at 8:41

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