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

5 files changed, 181 insertions, 13 deletions

diff --git a/src/table/Cargo.toml b/src/table/Cargo.toml
index 1963f3da..945763fa 100644
--- a/src/table/Cargo.toml
+++ b/src/table/Cargo.toml
@@ -21,6 +21,7 @@ rand = "0.7"
 hex = "0.3"
 arc-swap = "0.4"
 log = "0.4"
+hexdump = "0.1"
 
 sled = "0.31"
 
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()));
+				}
+			}
+		}
+	}
+}
diff --git a/src/table/lib.rs b/src/table/lib.rs
index 7684fe9d..704f8f1e 100644
--- a/src/table/lib.rs
+++ b/src/table/lib.rs
@@ -3,6 +3,7 @@
 #[macro_use]
 extern crate log;
 
+pub mod crdt;
 pub mod schema;
 pub mod util;
 
@@ -12,5 +13,5 @@ pub mod table_sharded;
 pub mod table_sync;
 
 pub use schema::*;
-pub use util::*;
 pub use table::*;
+pub use util::*;
diff --git a/src/table/schema.rs b/src/table/schema.rs
index 49cede0a..d2ec9450 100644
--- a/src/table/schema.rs
+++ b/src/table/schema.rs
@@ -20,7 +20,6 @@ impl PartitionKey for Hash {
 	}
 }
 
-
 pub trait SortKey {
 	fn sort_key(&self) -> &[u8];
 }
@@ -37,7 +36,6 @@ impl SortKey for Hash {
 	}
 }
 
-
 pub trait Entry<P: PartitionKey, S: SortKey>:
 	PartialEq + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync
 {
@@ -47,7 +45,6 @@ pub trait Entry<P: PartitionKey, S: SortKey>:
 	fn merge(&mut self, other: &Self);
 }
 
-
 #[async_trait]
 pub trait TableSchema: Send + Sync {
 	type P: PartitionKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
@@ -66,4 +63,3 @@ pub trait TableSchema: Send + Sync {
 		true
 	}
 }
-
diff --git a/src/table/table.rs b/src/table/table.rs
index 2beac3f4..5dfee3c8 100644
--- a/src/table/table.rs
+++ b/src/table/table.rs
@@ -2,6 +2,8 @@ use std::collections::{BTreeMap, HashMap};
 use std::sync::Arc;
 use std::time::Duration;
 
+use log::warn;
+
 use arc_swap::ArcSwapOption;
 use futures::stream::*;
 use serde::{Deserialize, Serialize};
@@ -185,7 +187,7 @@ where
 		for resp in resps {
 			if let TableRPC::ReadEntryResponse(value) = resp {
 				if let Some(v_bytes) = value {
-					let v = Self::decode_entry(v_bytes.as_slice())?;
+					let v = self.decode_entry(v_bytes.as_slice())?;
 					ret = match ret {
 						None => Some(v),
 						Some(mut x) => {
@@ -241,7 +243,7 @@ where
 		for resp in resps {
 			if let TableRPC::Update(entries) = resp {
 				for entry_bytes in entries.iter() {
-					let entry = Self::decode_entry(entry_bytes.as_slice())?;
+					let entry = self.decode_entry(entry_bytes.as_slice())?;
 					let entry_key = self.tree_key(entry.partition_key(), entry.sort_key());
 					match ret.remove(&entry_key) {
 						None => {
@@ -363,7 +365,7 @@ where
 			let keep = match filter {
 				None => true,
 				Some(f) => {
-					let entry = Self::decode_entry(value.as_ref())?;
+					let entry = self.decode_entry(value.as_ref())?;
 					F::matches_filter(&entry, f)
 				}
 			};
@@ -382,14 +384,14 @@ where
 		let mut epidemic_propagate = vec![];
 
 		for update_bytes in entries.iter() {
-			let update = Self::decode_entry(update_bytes.as_slice())?;
+			let update = self.decode_entry(update_bytes.as_slice())?;
 
 			let tree_key = self.tree_key(update.partition_key(), update.sort_key());
 
 			let (old_entry, new_entry) = self.store.transaction(|db| {
 				let (old_entry, new_entry) = match db.get(&tree_key)? {
 					Some(prev_bytes) => {
-						let old_entry = Self::decode_entry(&prev_bytes)
+						let old_entry = self.decode_entry(&prev_bytes)
 							.map_err(sled::ConflictableTransactionError::Abort)?;
 						let mut new_entry = old_entry.clone();
 						new_entry.merge(&update);
@@ -437,7 +439,7 @@ where
 				break;
 			}
 			if let Some(old_val) = self.store.remove(&key)? {
-				let old_entry = Self::decode_entry(&old_val)?;
+				let old_entry = self.decode_entry(&old_val)?;
 				self.instance.updated(Some(old_entry), None).await?;
 				self.system
 					.background
@@ -455,12 +457,18 @@ where
 		ret
 	}
 
-	fn decode_entry(bytes: &[u8]) -> Result<F::E, Error> {
+	fn decode_entry(&self, bytes: &[u8]) -> Result<F::E, Error> {
 		match rmp_serde::decode::from_read_ref::<_, F::E>(bytes) {
 			Ok(x) => Ok(x),
 			Err(e) => match F::try_migrate(bytes) {
 				Some(x) => Ok(x),
-				None => Err(e.into()),
+				None => {
+					warn!("Unable to decode entry of {}: {}", self.name, e);
+					for line in hexdump::hexdump_iter(bytes) {
+						debug!("{}", line);
+					}
+					Err(e.into())
+				}
 			},
 		}
 	}