[erlang-questions] simple virtual file system in Erlang?

Joe Armstrong erlang@REDACTED
Sun Mar 26 19:31:02 CEST 2017

Somebody  tweeted me me a link to upspin.io


This has a very good way of naming files - well worth reading


On Sun, Mar 26, 2017 at 8:31 AM, Joe Armstrong <erlang@REDACTED> wrote:
> Yes - mapping the path to a content addressable store address would be
> great. It would also be great in a wider context.
> A fun extension would be to add a an http interface. Something like
>    POST <blob>
> To store <blob>,  then later
>    GET /blob/sha256/<SHA>
> to recover the blob. <SHA> is the SHA256 checksum of the data (the
> path contains the
> type of the checksum - so you might say GETblob/md5/<MD5CHECKSUM>
> then add a DHT - then run on every webserver on the planet
> then store all data forever.
> The nice thing about this is that it's self-securing - a person-in-the-middle
> cannot change the data without it being detected (since you can check
> the SHA of the
> data when you get it back)
> Such a system has three relatively simple layers
> - transport (say HTTP over TCP)
> - DHT
> - storage
> If you ask Jesper nicely he'll tell you all about DHT's :-)
> Have fun with the storage layer for this (and no it's NOT a toy project)
> /Joe
> On Sun, Mar 26, 2017 at 7:57 AM, Jesper Louis Andersen
> <jesper.louis.andersen@REDACTED> wrote:
>> The simplest way is probably to map a path to its data, where the path is a
>> list of components. That is, the UNIX file ls in /usr/bin would be
>> represented as ["usr", "bin", "ls"].
>> But you could also go the way of Plan9's venti. Map something like ["usr",
>> "bin", "ls"] into a sha3 checksum of the data currently residing in the file
>> and keep the data inside a storage suitable for storing data by its content
>> addressing. venti also extends this by storing a tree of 64 kilobyte blocks
>> which can then be regarded as the data when taken together. Thus, you have
>> two components: the data store, and the path mapping service, mapping a path
>> to the underlying data.
>> This idea has the advantage of being practically useful in many situations
>> beside a toy example :)
>> On Sun, Mar 26, 2017 at 2:46 PM Marco Molteni <marco.molteni@REDACTED>
>> wrote:
>>> Hello colleagues,
>>> I would like to start from the presentation "Build an FTP Server with
>>> Ranch in 30 Minutes" and really build an FTP server, so at a certain point I
>>> need to hit the filesystem.
>>> Since the idea is still as a presentation (as opposed to building a
>>> production FTP server) I don't want to touch the real filesystem of the
>>> host, I want to use a as simple as possible virtual filesystem. It could be
>>> backed by DETS or Mnesia for example, or it could stay only in memory.
>>> On the other hand, it must still behave as a filesystem, that is, it must
>>> be hierarchical, so a direct mapping to a key/value store would not be
>>> enough. In the spirit of simplicity, I don't need any concept of read/write
>>> permission, I simply need a sort of graph with two types: inner nodes are
>>> directories, leaf nodes are files or empty directories.
>>> I am thinking to use DETS and somehow introduce a very simple intermediate
>>> layer that would offer the impression to be in a graph (each non-leaf node a
>>> directory) and map it to the DETS key/value API.
>>> Any suggestions?
>>> thanks
>>> marco
>>> [1] https://ninenines.eu/articles/ranch-ftp/
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