[darcs-users] decentralized darcs repository

Zooko O'Whielacronx zookog at gmail.com
Thu Jan 15 13:30:19 UTC 2009


Folks:

This is a decentralized darcs repository:

http://testgrid.allmydata.org:3567/uri/URI:DIR2-RO:gmct6zvaaontfme7pokrcyseje:lfqgih5hsyvi6aazicelbigm4ldzzdqkkjlsylnl6xnai6holr2q

It contains the darcs source code and revision control history.

There are several cool things about storing a darcs repository on Tahoe:

cool thing #1: Each file is split into 10 pieces, each piece is stored on a
different storage server, and any 3 of those pieces are sufficient to
download the file.  Therefore, the loss of any 7 of the storage servers will
not destroy the file.

cool thing #2: That URL contains the fingerprint of a public key, and all
files stored in that directory are signed by that public key.  The holder of
the corresponding private key can upload new files into the directory or
change the contents of files in the directory -- other people can't.

cool thing #3: That URL contains a symmetric encryption secret, and all
files stored in that directory are encrypted with it.  If you give the URL
to someone, they can read the contents of the files, but if they aren't
given the URL, they can't.  The operators of the storage servers which are
storing the files can't (unless someone gives them the URL).  This isn't
especially useful for the darcs darcs repository, but you could imagine if
you had a private repository that you didn't want the world to see, you
could use this property.

There's one not-so-cool thing about it: it is slow!  I assume that the slow
speed of "darcs get --lazy
http://testgrid.allmydata.org:3567/uri/URI:DIR2-RO:gmct6zvaaontfme7pokrcyseje:lfqgih5hsyvi6aazicelbigm4ldzzdqkkjlsylnl6xnai6holr2q"
is due to the combination of darcs making many separate requests and Tahoe
taking a fraction of a second longer to answer each one than Apache would.
That's only an assumption on my part, though -- actual timings or other
diagnostics would be appreciated.

Here's the decentralized darcs repository containing the Tahoe source code:

http://testgrid.allmydata.org:3567/uri/URI%3ADIR2-RO%3Avf42lud2e5vvw237c7vyc5lotq%3At2nkfthjj5lhdgqqd4rtweazp3f2kltyhqecwwa2njj7suhjuy3q/

Have fun!

Regards,

Zooko
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