We're using petgraph to encode an operation based CRDT (each graph node
is an operation) as a DAG, and one of the important things to ensure
is that the final state is not influenced by the order of concurrent
operations. In this case a concurrent operation would mean two potential
graph traversal orders, as there's no direct edge between the two
concurrent ops. This is essential a "partial order" of operations.
To be able to test this, we'd want some kind of control over how
neighbors are iterated over I guess, when there's more than one possible
sort order. Say we have a graph like this:
┌────────b◄─────┐
▼ │
a d
▲ │
└────────c◄─────┘
There are two possible topological traverse orders: [a, b, c, d] and [a,
c, b, d]. Having a way to go through these different orders would
be super handy.
One option would be to allow random order traversal. This would allow us
to test all orders by running the test enough times to likely test all
permutations.
Since petgraph doesn't support this, we implement our own simple DAG in
`radicle-dag`, which implements random-order topological orders.
For now, we don't make explicit use of these improvements, we simply
replace the underlying graph with our own.
Sometimes it is more efficient to perform multiple operations at once
and store those in the collaborative object graph together.
Change the contents to be a non-empty sequence of byte sequences,
i.e. NonEmpty<Vec<u8>>. These are stored as blobs in a git tree in
order by their index in the non-empty sequence. They are, in turn,
retrieved in order of their original index.
Change the conversion of an `EntryWithClock` to return a non-empty
sequence of `Op`s, which are in turn used to apply many changes in
each `from_history` implementation.
Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett
The latter is a fork of the former, which adds const generics
and a bunch of other quality of life improvements that aren't
in the original crate due to it being unmaintained.
Signed-off-by: Alexis Sellier <alexis@radicle.xyz>
Add quickcheck tests for parse_refstr to ensure the correct
behaviour.
This required adding Arbitrary instances for TypeName and ObjectId, as
well as adding a mechanism for generating Invalid ObjectIds.
Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett
This is a minimal port of the collaborative objects code from
radicle-link[0].
A `CollaborativeObject` is made up of a `History` of `Change`s that
are expected to be stored in a `git` backend.
The library exposes a CRU series of functions `create`, `get`, `list`,
and `update`.
This implementation differs, to previous one, in that it does not
assume any kind of identity system -- its only assumption is that
identities have an identifier and can be addressed in the `git`
database. This means that it does not require an `author` to be passed
in and it only uses the `resource` (previously `authorizing_identity`)
to store its content-address in the `Change`.
It also foregoes any caching to simplify the port and not make any
early optimisation assumptions.
[0]: https://github.com/radicle-dev/radicle-link/tree/master/cob
Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
Alexis Sellier
Fintan Halpenny
Dr Maxim Orlovsky