Merge pull request 'ReplicationMode -> ConsistencyMode+ReplicationFactor' (#750) from yuka/garage:split-consistency-mode into next-0.10

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/750

1 files changed, 78 insertions, 41 deletions

diff --git a/src/rpc/replication_mode.rs b/src/rpc/replication_mode.rs
index b142ea10..a3a94085 100644
--- a/src/rpc/replication_mode.rs
+++ b/src/rpc/replication_mode.rs
@@ -1,57 +1,94 @@
-#[derive(Clone, Copy)]
-pub enum ReplicationMode {
-	None,
-	TwoWay,
-	TwoWayDangerous,
-	ThreeWay,
-	ThreeWayDegraded,
-	ThreeWayDangerous,
+use garage_util::config::Config;
+use garage_util::crdt::AutoCrdt;
+use garage_util::error::*;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct ReplicationFactor(usize);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Default, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum ConsistencyMode {
+	/// Read- and Write-quorum are 1
+	Dangerous,
+	/// Read-quorum is 1
+	Degraded,
+	/// Read- and Write-quorum are determined for read-after-write-consistency
+	#[default]
+	Consistent,
+}
+
+impl ConsistencyMode {
+	pub fn parse(s: &str) -> Option<Self> {
+		serde_json::from_value(serde_json::Value::String(s.to_string())).ok()
+	}
+}
+
+impl AutoCrdt for ConsistencyMode {
+	const WARN_IF_DIFFERENT: bool = true;
 }
 
-impl ReplicationMode {
-	pub fn parse(v: &str) -> Option<Self> {
-		match v {
-			"none" | "1" => Some(Self::None),
-			"2" => Some(Self::TwoWay),
-			"2-dangerous" => Some(Self::TwoWayDangerous),
-			"3" => Some(Self::ThreeWay),
-			"3-degraded" => Some(Self::ThreeWayDegraded),
-			"3-dangerous" => Some(Self::ThreeWayDangerous),
-			_ => None,
+impl ReplicationFactor {
+	pub fn new(replication_factor: usize) -> Option<Self> {
+		if replication_factor < 1 {
+			None
+		} else {
+			Some(Self(replication_factor))
 		}
 	}
 
 	pub fn replication_factor(&self) -> usize {
-		match self {
-			Self::None => 1,
-			Self::TwoWay | Self::TwoWayDangerous => 2,
-			Self::ThreeWay | Self::ThreeWayDegraded | Self::ThreeWayDangerous => 3,
-		}
+		self.0
 	}
 
-	pub fn read_quorum(&self) -> usize {
-		match self {
-			Self::None => 1,
-			Self::TwoWay | Self::TwoWayDangerous => 1,
-			Self::ThreeWay => 2,
-			Self::ThreeWayDegraded | Self::ThreeWayDangerous => 1,
+	pub fn read_quorum(&self, consistency_mode: ConsistencyMode) -> usize {
+		match consistency_mode {
+			ConsistencyMode::Dangerous | ConsistencyMode::Degraded => 1,
+			ConsistencyMode::Consistent => self.replication_factor().div_ceil(2),
 		}
 	}
 
-	pub fn write_quorum(&self) -> usize {
-		match self {
-			Self::None => 1,
-			Self::TwoWay => 2,
-			Self::TwoWayDangerous => 1,
-			Self::ThreeWay | Self::ThreeWayDegraded => 2,
-			Self::ThreeWayDangerous => 1,
+	pub fn write_quorum(&self, consistency_mode: ConsistencyMode) -> usize {
+		match consistency_mode {
+			ConsistencyMode::Dangerous => 1,
+			ConsistencyMode::Degraded | ConsistencyMode::Consistent => {
+				(self.replication_factor() + 1) - self.read_quorum(ConsistencyMode::Consistent)
+			}
 		}
 	}
+}
 
-	pub fn is_read_after_write_consistent(&self) -> bool {
-		match self {
-			Self::None | Self::TwoWay | Self::ThreeWay => true,
-			_ => false,
-		}
+impl std::convert::From<ReplicationFactor> for usize {
+	fn from(replication_factor: ReplicationFactor) -> usize {
+		replication_factor.0
 	}
 }
+
+pub fn parse_replication_mode(
+	config: &Config,
+) -> Result<(ReplicationFactor, ConsistencyMode), Error> {
+	match (&config.replication_mode, config.replication_factor, config.consistency_mode.as_str()) {
+        (Some(replication_mode), None, "consistent") => {
+            tracing::warn!("Legacy config option replication_mode in use. Please migrate to replication_factor and consistency_mode");
+            let parsed_replication_mode = match replication_mode.as_str() {
+                "1" | "none"  => Some((ReplicationFactor(1), ConsistencyMode::Consistent)),
+                "2"           => Some((ReplicationFactor(2), ConsistencyMode::Consistent)),
+                "2-dangerous" => Some((ReplicationFactor(2), ConsistencyMode::Dangerous)),
+                "3"           => Some((ReplicationFactor(3), ConsistencyMode::Consistent)),
+                "3-degraded"  => Some((ReplicationFactor(3), ConsistencyMode::Degraded)),
+                "3-dangerous" => Some((ReplicationFactor(3), ConsistencyMode::Dangerous)),
+                _ => None,
+            };
+            Some(parsed_replication_mode.ok_or_message("Invalid replication_mode in config file.")?)
+        },
+        (None, Some(replication_factor), consistency_mode) => {
+            let replication_factor = ReplicationFactor::new(replication_factor)
+                .ok_or_message("Invalid replication_factor in config file.")?;
+            let consistency_mode = ConsistencyMode::parse(consistency_mode)
+                .ok_or_message("Invalid consistency_mode in config file.")?;
+            Some((replication_factor, consistency_mode))
+        }
+        _ => None,
+    }.ok_or_message("Either the legacy replication_mode or replication_level and consistency_mode can be set, not both.")
+}