mongofuse

A FUSE filesystem, powered by MongoDB and written in Node.js. Mostly an exercise for me to learn MongoDB and Node.js. It aims towards POSIX functionality for use as a regular filesystem.

Starting

If cloned from GitHub, you'll need to run npm install from the directory of your clone, then any of:

• npm start connection-string mountpoint [-o option[,option]...]
• node index.js connection-string mountpoint [-o option[,option]...]
• ./index.js connection-string mountpoint [-o option[,option]...]

You can also install globally with npm install -g mongofuse, in which case run:

• mongofuse connection-string mountpoint [-o option[,option]...]

where connection-string is a MongoDB connection string (maybe just mongofuse to use a database called mongofuse on an instance running on localhost on the standard port) and mountpoint is an existing directory where the filesystem is to be mounted. Mount options can be some of these, as also linked from the fuse-bindings readme.

Use with macOS / OS X

You will need to install OSXFuse and pkg-config. If you use Homebrew, you can do this with brew cask install osxfuse and brew install pkg-config. You will need to authorise the kext in System Preferences.

Use within a docker container

Make sure you add the following params on the docker run command: --cap-add=MKNOD --cap-add=SYS_ADMIN --device=/dev/fuse

Things that work

• The root directory is now created automatically when you start mongofuse with an empty database. This means you can actually try using it without manually inserting stuff into MongoDB first!
• The usual reading, writing, creating, deleting, renaming etc. of files and directories
• chmod, chown, chgrp (including updating ctime)
• mknod (special files can be created, but can't be used with nodev in effect, see below)
• mtime/ctime update on file write
• atime update on file read, directory list, symlink resolution. atime/relatime/noatime options.
• symlinks and hardlinks (won't hardlink directories)
• File permissions enforced on open, truncate, ftruncate. Directory permissions enforced on opendir. access function is implemented. You can't read from a fd opened with O_WRONLY and vice versa. You can't chmod/chown/chgrp when you shouldn't be allowed to.
• Accepts basic FUSE mount options on the command line (eg. -o allow_other)
• The size is now stored explicitly in the inode, avoiding looking up the data if it's only the attributes we're interested in.
• Extended attributes
• Works with macOS (using OSXFuse) as well as Linux

Things that don't work / aren't present (yet)

• Directory permissions are partially but not fully enforced. You can traverse and create/delete files in any directory, although reading/listing permissions are enforced. (Mounting with the default_permissions option is a possible solution.)
• Directory mtimes/ctimes aren't updated when a file is created.
• When I repeatedly touch a file without specifying a time, the atime/mtime that are passed to my utimens function jump about non-monotonically over a number of minutes. They can also be a number of minutes away from Date.now() which is what the ctime gets set to. I don't think my filesystem is to blame.
• Files larger than just under 16MB, due to the maximum document size in MongoDB. I now check for this and return EFBIG from ftruncate/truncate/write. The solution to this is GridFS.
• Not yet tested on Windows, but may work with Dokany.
• Performance is probably pants, due to things like lack of caching, and storing the data itself within the inode document.