RiakFS

RiakFS is an implementation of filesystem in Riak that emulates node.js fs module. The following methods are implemented:

• open
• close
• read
• write
• readdir
• mkdir
• rmdir
• rename
• unlink
• stat
• fstat
• utimes
• futimes
• appendFile
• exists
• createReadStream
• createWriteStream

It also adds some convenient methods like:

• makeTree - recursively create directory tree
• copy - copy files (within same riakfs)
• updateMeta and setMeta - manipulate custom metadata saved with files
• share - share directory with another riakfs

All methods will return a promise as well as call a usual callback

Implementation

Files are stored in two buckets: fs.files and fs.chunks (you can use your own names with root option, see example below). First one is used for storing file metadata such as file size, mtime, ctime, contentType, etc as well as parent directory index (2i). Keys in fs.files bucket are full file paths ('/a/b/c/d.txt'). Actual file data is divided into chunks (256kb each) and stored in fs.chunks bucket.

RiakFS makes use of Riak 2i (secondary indexes) so it requires LevelDB backend. 2i is only used for finding directory contents (e.g. readdir).

Siblings resolution

RiakFS uses allow_mult=true for its files (file meta information) bucket and tries to resolve possible siblings during read operations. RiakFS will handle tombstones conflicts (for example when doing mkdir immediately after rmdir).

Both buckets use allow_mult=false. I'm going to change this as soon as I have better siblings resolution pattern.

Installation

$ npm install riakfs

Example

open/write/close:

require('riakfs').create({
    root: 'test-fs' // root is a bucket name prefix, bucket names will be: test-fs.files, test-fs.chunks
})
.then(function(riakfs){
    return riakfs.open('/testFile', 'w').then(function(fd){
        return riakfs.write(fd, 'test', 0, 4, null).then(function() {
            return riakfs.close(fd)
        })
    })
})

writeFile (copy file from hard drive):

Promise.promisify(fs.readFile)('/someFile.jpg').then(function(data) {
    return riakfs.writeFile('/someFile.jpg', data)
})

streams:

var readStream = fs.createReadStream('/someFile.jpg')
var writeStream = riakfs.createWriteStream('/someFile.jpg')

readStream.pipe(writeStream)

writeStream.on('close', function() {
    // done!
})

You can also save some custom meta information with files by passing an object instead of string path to open, writeFile or createWriteStream:

var file = {
    filename: '/testFile',
    meta: {
        someKey: 'someValue',
        otherKey: {
            subKey: 'subValue'
        }
    }
}
return riakfs.open(file, 'w').then(function(fd){
    ...
})

or use updateMeta and setMeta methods

Saved metadata can be retrieved with a stat or open calls:

return riakfs.stat('/testFile').then(function(stats){
    // stats.file.meta
})

return riakfs.open('/testFile').then(function(fd){
    // fd.file.meta
})

See tests for more.

Events

RiakFS can optionally trigger events on file/dir changes:

// pass events: true option to enable events
return riakfs.create({ events: true }).then(function(fs){
    fs.on('change', function(filename, info) { // triggered when file data is changed
    })

    fs.on('new', function(filename, info) { // triggered when new file or directory is created
    })

    fs.on('rename', function(old, _new, info) { // triggered when file or dir is renamed
    })

    fs.on('delete', function(filename, info) { // triggered when file or directory is deleted
    })
})

Shared directories

RiakFS allows sharing directories between different filesystems (those with different root option). Given two filesystems: fs1 and fs2, one can share some directory from fs1 like this:

fs1.share('/some/dir', fs2.options.root, 'alias')

or readonly:

fs1.share('/some/dir', fs2.options.root, 'alias', true)

This will create a directory named /Shared/alias in fs1.

You can read sharing info by stating on shared directories from both filesystems:

from fs1:

fs1.stat('/some/dir').then(function(stats){
    // read stats.file.share:
    /*
    {
        to: [ { root: 'fs2-root', alias: 'alias', readOnly: false } ],
        owner: { root: 'fs1-root', path: '/some/dir' }
    }
     */
})

same result from fs2:

fs2.stat('/Shared/alias').then(function(stats){
    // read stats.file.share:
    /*
    {
        to: [ { root: 'fs2-root', alias: 'alias', readOnly: false } ],
        owner: { root: 'fs1-root', path: '/some/dir' }
    }
     */
})

Cancel sharing:

from fs1:

fs1.unshare('/some/dir', fs2.options.root) // this will cancel sharing with fs2

from fs2:

fs2.unshare('/Shared/alias')

Initializing filesystems for shared dirs

Your application should provide a function that should return a promise for RiakFS instance for specified root, example:

require('riakfs').create({ root: someId, events: true,
    shared: {
        fs: function(_root){
            // return riakfs instance for specified `root` = _root
        }
    }
})

Trash

RiakFs allows to move files to /.Trash upon removal. Just enable trash support when initialising riakfs:

require('riakfs').create({ root: someId, trash: true })

Files are not removed automatically by RiakFs from /.Trash so your application should take care of this. You can use mtime to detect when file was removed.

Application

The idea is that this module (connected riakfs instance) can be used as a drop-in replacement for node fs module.

Status

Not tested in production yet. Under development. Pull requests are welcomed.

Riak settings

I suggest to increase erlang network buffer size (See: http://www.erlang.org/doc/man/erl.html#%2bzdbbl)

• In version 1.4.x this parameter is located in vm.args file. The value is in kilobytes (so 32768 - 32MB).
• In version 2.0 the parameter is called erlang.distribution_buffer_size, should be put in riak.conf and the value is in bytes (33554432 = 32MB).

Authors

• Oleksiy Krivoshey https://github.com/oleksiyk

License (MIT)

Copyright (c) 2014 Oleksiy Krivoshey.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.