Improve how node roles are assigned in Garagev0.5-beta1

- change the terminology: the network configuration becomes the role
  table, the configuration of a nodes becomes a node's role
- the modification of the role table takes place in two steps: first,
  changes are staged in a CRDT data structure. Then, once the user is
  happy with the changes, they can commit them all at once (or revert
  them).
- update documentation
- fix tests
- implement smarter partition assignation algorithm

This patch breaks the format of the network configuration: when
migrating, the cluster will be in a state where no roles are assigned.
All roles must be re-assigned and commited at once. This migration
should not pose an issue.

1 files changed, 23 insertions, 0 deletions

diff --git a/src/util/crdt/mod.rs b/src/util/crdt/mod.rs
new file mode 100644
index 00000000..9663a5a5
--- /dev/null
+++ b/src/util/crdt/mod.rs
@@ -0,0 +1,23 @@
+//! This package provides a simple implementation of conflict-free replicated data types (CRDTs)
+//!
+//! CRDTs are a type of data structures that do not require coordination.  In other words, we can
+//! edit them in parallel, we will always find a way to merge it.
+//!
+//! A general example is a counter. Its initial value is 0.  Alice and Bob get a copy of the
+//! counter.  Alice does +1 on her copy, she reads 1.  Bob does +3 on his copy, he reads 3.  Now,
+//! it is easy to merge their counters, order does not count: we always get 4.
+//!
+//! Learn more about CRDT [on Wikipedia](https://en.wikipedia.org/wiki/Conflict-free_replicated_data_type)
+
+mod bool;
+#[allow(clippy::module_inception)]
+mod crdt;
+mod lww;
+mod lww_map;
+mod map;
+
+pub use self::bool::*;
+pub use crdt::*;
+pub use lww::*;
+pub use lww_map::*;
+pub use map::*;