CassFS

CassFS is a fuse filesystem that uses Cassandra as the storage engine. It has a concept of owners and environments to support multi-tenency. The idea is based on the concept of the Valhalla filesystem created by Pantheon. Except that they use a webdav mounted filesystem, and a lot on the server side. CassFS interacts directly with Cassandra.

All of the normal rules apply when talking about any new filesystem.

• Do not keep important data on it, you will likely lose any data at this point
• The schema and data structures are not stable, so breaking changes will likely occur
• There is no guarantee or warranty for stability or safety in using this software

Why?

To be able to run something like drupal or wordpress in a container without having to set up a distributed file system. If you need to support running a database or some other persistent datastore with large files, this is not intended for that use. The blog from Pantheon does a very good job describing the type of behaviour that this is suited for. It is best for smaller files, more reads than writes, and when there are writes they are of the entire file.

Use

This is how I have been testing it, running an apache/php container and drupal from the file system.

Start it with cassfs [options]

To stop it run fusermout -u <moutnpoint>

The options are:

  -debug
        Turn on debugging
  -entry_ttl float
        fuse entry cache TTL. (default 1)
  -environment string
        Environment to mount (default "prod")
  -keyspace string
        Keyspace to use for the filesystem (default "cassfs")
  -mount string
        Mount directory (default "./")
  -negative_ttl float
        fuse negative entry cache TTL. (default 1)
  -fcache_ttl
        Seconds to keep local cache of files and metadata, defaults to 60 seconds
  -owner int
        ID of the FS owner (default 1)
  -server string
        Cassandra server to connect to (default "localhost")

Example Usage with Local Caching

go-fuse, one of the required modules includes a unionfs example. This will locally cache files, using both should provide a significant performance boost for sites with enough traffic where the cache would be able to serve files.

In my testing on CentOS, you need to be sure to run this to allow docker to be able to read from a fuse mount setsebool virt_use_fusefs true

Build

Requires Go 1.6

# Glide - Update a project's dependencies
glide update

# Build binary for OS X
make osx

#Build binary for Linux
make linux

Local Test Env

docker-compose up -d
make linux
docker-compose exec cassandra cqlsh -f /opt/cassfs.cql
./cassfs -mount /opt -keyspace cassfs

Todo

This is still very early on, so there are surely many thing that I have not even thought of. This list is really too long to get right on the first pass, but here are a few of the things.

1. Testing
2. Caching?
3. docker/kubernetes integration
4. Mount script
5. More robust options handling (Environment variables)