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authorAlex Auvolat <alex@adnab.me>2021-11-09 12:24:04 +0100
committerAlex Auvolat <alex@adnab.me>2021-11-16 16:05:53 +0100
commitc94406f4282d48e2e2ac82ffb57eafaad23f7edc (patch)
tree01fe1b272e18fdae993e2207d8d3aea4a301ec56 /src/table/crdt/crdt.rs
parent53888995bdd7c672d2e3ab8bb6a3529195c127a9 (diff)
downloadgarage-c94406f4282d48e2e2ac82ffb57eafaad23f7edc.tar.gz
garage-c94406f4282d48e2e2ac82ffb57eafaad23f7edc.zip
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.
Diffstat (limited to 'src/table/crdt/crdt.rs')
-rw-r--r--src/table/crdt/crdt.rs71
1 files changed, 0 insertions, 71 deletions
diff --git a/src/table/crdt/crdt.rs b/src/table/crdt/crdt.rs
deleted file mode 100644
index a8f1b9aa..00000000
--- a/src/table/crdt/crdt.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-use garage_util::data::*;
-
-/// Definition of a CRDT - all CRDT Rust types implement this.
-///
-/// A CRDT is defined as a merge operator that respects a certain set of axioms.
-///
-/// In particular, the merge operator must be commutative, associative,
-/// idempotent, and monotonic.
-/// In other words, if `a`, `b` and `c` are CRDTs, and `⊔` denotes the merge operator,
-/// the following axioms must apply:
-///
-/// ```text
-/// a ⊔ b = b ⊔ a (commutativity)
-/// (a ⊔ b) ⊔ c = a ⊔ (b ⊔ c) (associativity)
-/// (a ⊔ b) ⊔ b = a ⊔ b (idempotence)
-/// ```
-///
-/// Moreover, the relationship `≥` defined by `a ≥ b ⇔ ∃c. a = b ⊔ c` must be a partial order.
-/// This implies a few properties such as: if `a ⊔ b ≠ a`, then there is no `c` such that `(a ⊔ b) ⊔ c = a`,
-/// as this would imply a cycle in the partial order.
-pub trait Crdt {
- /// Merge the two datastructures according to the CRDT rules.
- /// `self` is modified to contain the merged CRDT value. `other` is not modified.
- ///
- /// # Arguments
- ///
- /// * `other` - the other CRDT we wish to merge with
- fn merge(&mut self, other: &Self);
-}
-
-/// All types that implement `Ord` (a total order) can also implement a trivial CRDT
-/// defined by the merge rule: `a ⊔ b = max(a, b)`. Implement this trait for your type
-/// to enable this behavior.
-pub trait AutoCrdt: Ord + Clone + std::fmt::Debug {
- /// WARN_IF_DIFFERENT: emit a warning when values differ. Set this to true if
- /// different values in your application should never happen. Set this to false
- /// if you are actually relying on the semantics of `a ⊔ b = max(a, b)`.
- const WARN_IF_DIFFERENT: bool;
-}
-
-impl<T> Crdt for T
-where
- T: AutoCrdt,
-{
- fn merge(&mut self, other: &Self) {
- if Self::WARN_IF_DIFFERENT && self != other {
- warn!(
- "Different CRDT values should be the same (logic error!): {:?} vs {:?}",
- self, other
- );
- if other > self {
- *self = other.clone();
- }
- warn!("Making an arbitrary choice: {:?}", self);
- } else if other > self {
- *self = other.clone();
- }
- }
-}
-
-impl AutoCrdt for String {
- const WARN_IF_DIFFERENT: bool = true;
-}
-
-impl AutoCrdt for bool {
- const WARN_IF_DIFFERENT: bool = true;
-}
-
-impl AutoCrdt for FixedBytes32 {
- const WARN_IF_DIFFERENT: bool = true;
-}