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authorAlex <alex@adnab.me>2020-11-21 16:01:26 +0100
committerAlex <alex@adnab.me>2020-11-21 16:01:26 +0100
commitb3814b15ccc233d7c4233b43816cce20db278f17 (patch)
treef37a1ce39bfae7c3f706162e186df4064635bd74 /src/table/crdt.rs
parent5dc304ac41c2ae0699fbdd56117b60c517a1ad39 (diff)
parenta8b3c8fd5898400d64310f61bb1a41dd5fefe5ea (diff)
downloadgarage-b3814b15ccc233d7c4233b43816cce20db278f17.tar.gz
garage-b3814b15ccc233d7c4233b43816cce20db278f17.zip
Merge pull request 'Use cleaner CRDT data types for objects to avoid accidents like #16' (#18) from feature/better-crdt into master
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/18
Diffstat (limited to 'src/table/crdt.rs')
-rw-r--r--src/table/crdt.rs162
1 files changed, 162 insertions, 0 deletions
diff --git a/src/table/crdt.rs b/src/table/crdt.rs
new file mode 100644
index 00000000..2b903cf0
--- /dev/null
+++ b/src/table/crdt.rs
@@ -0,0 +1,162 @@
+use serde::{Deserialize, Serialize};
+
+use garage_util::data::*;
+
+pub trait CRDT {
+ fn merge(&mut self, other: &Self);
+}
+
+impl<T> CRDT for T
+where
+ T: Ord + Clone,
+{
+ fn merge(&mut self, other: &Self) {
+ if other > self {
+ *self = other.clone();
+ }
+ }
+}
+
+// ---- LWW Register ----
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct LWW<T> {
+ ts: u64,
+ v: T,
+}
+
+impl<T> LWW<T>
+where
+ T: CRDT,
+{
+ pub fn new(value: T) -> Self {
+ Self {
+ ts: now_msec(),
+ v: value,
+ }
+ }
+ pub fn migrate_from_raw(ts: u64, value: T) -> Self {
+ Self { ts, v: value }
+ }
+ pub fn update(&mut self, new_value: T) {
+ self.ts = std::cmp::max(self.ts + 1, now_msec());
+ self.v = new_value;
+ }
+ pub fn get(&self) -> &T {
+ &self.v
+ }
+ pub fn get_mut(&mut self) -> &mut T {
+ &mut self.v
+ }
+}
+
+impl<T> CRDT for LWW<T>
+where
+ T: Clone + CRDT,
+{
+ fn merge(&mut self, other: &Self) {
+ if other.ts > self.ts {
+ self.ts = other.ts;
+ self.v = other.v.clone();
+ } else if other.ts == self.ts {
+ self.v.merge(&other.v);
+ }
+ }
+}
+
+// ---- Boolean (true as absorbing state) ----
+
+#[derive(Clone, Copy, Debug, Serialize, Deserialize, PartialEq)]
+pub struct Bool(bool);
+
+impl Bool {
+ pub fn new(b: bool) -> Self {
+ Self(b)
+ }
+ pub fn set(&mut self) {
+ self.0 = true;
+ }
+ pub fn get(&self) -> bool {
+ self.0
+ }
+}
+
+impl CRDT for Bool {
+ fn merge(&mut self, other: &Self) {
+ self.0 = self.0 || other.0;
+ }
+}
+
+// ---- LWW Map ----
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct LWWMap<K, V> {
+ vals: Vec<(K, u64, V)>,
+}
+
+impl<K, V> LWWMap<K, V>
+where
+ K: Ord,
+ V: CRDT,
+{
+ pub fn new() -> Self {
+ Self { vals: vec![] }
+ }
+ pub fn migrate_from_raw_item(k: K, ts: u64, v: V) -> Self {
+ Self {
+ vals: vec![(k, ts, v)],
+ }
+ }
+ pub fn take_and_clear(&mut self) -> Self {
+ let vals = std::mem::replace(&mut self.vals, vec![]);
+ Self { vals }
+ }
+ pub fn clear(&mut self) {
+ self.vals.clear();
+ }
+ pub fn update_mutator(&self, k: K, new_v: V) -> Self {
+ let new_vals = match self.vals.binary_search_by(|(k2, _, _)| k2.cmp(&k)) {
+ Ok(i) => {
+ let (_, old_ts, _) = self.vals[i];
+ let new_ts = std::cmp::max(old_ts + 1, now_msec());
+ vec![(k, new_ts, new_v)]
+ }
+ Err(_) => vec![(k, now_msec(), new_v)],
+ };
+ Self { vals: new_vals }
+ }
+ pub fn get(&self, k: &K) -> Option<&V> {
+ match self.vals.binary_search_by(|(k2, _, _)| k2.cmp(&k)) {
+ Ok(i) => Some(&self.vals[i].2),
+ Err(_) => None,
+ }
+ }
+ pub fn items(&self) -> &[(K, u64, V)] {
+ &self.vals[..]
+ }
+}
+
+impl<K, V> CRDT for LWWMap<K, V>
+where
+ K: Clone + Ord,
+ V: Clone + CRDT,
+{
+ fn merge(&mut self, other: &Self) {
+ for (k, ts2, v2) in other.vals.iter() {
+ match self.vals.binary_search_by(|(k2, _, _)| k2.cmp(&k)) {
+ Ok(i) => {
+ let (_, ts1, _v1) = &self.vals[i];
+ if ts2 > ts1 {
+ self.vals[i].1 = *ts2;
+ self.vals[i].2 = v2.clone();
+ } else if ts1 == ts2 {
+ self.vals[i].2.merge(&v2);
+ }
+ }
+ Err(i) => {
+ self.vals.insert(i, (k.clone(), *ts2, v2.clone()));
+ }
+ }
+ }
+ }
+}