define a separate enum for the monotonic/non-monotonic read flag

src/api/k2v/batch.rs

@@ -5,6 +5,7 @@ use serde::{Deserialize, Serialize};
 use garage_table::{EnumerationOrder, TableSchema};
 
 use garage_model::k2v::item_table::*;
+use garage_model::k2v::rpc::K2VMonotonicRead;
 
 use garage_api_common::helpers::*;
 
@@ -68,7 +69,7 @@ pub async fn handle_read_batch(
 async fn handle_read_batch_query(
 	ctx: &ReqCtx,
 	query: ReadBatchQuery,
-	monotonic_read: bool,
+	monotonic_read: K2VMonotonicRead,
 ) -> Result<ReadBatchResponse, Error> {
 	let ReqCtx {
 		garage, bucket_id, ..
@@ -92,10 +93,11 @@ async fn handle_read_batch_query(
 			.start
 			.as_ref()
 			.ok_or_bad_request("start should be specified if single_item is set")?;
-		let item = if monotonic_read {
+		let item = match monotonic_read {
-			garage.k2v.item_table.get_monotonic(&partition, sk).await?
+			K2VMonotonicRead::Monotonic => {
-		} else {
+				garage.k2v.item_table.get_monotonic(&partition, sk).await?
-			garage.k2v.item_table.get(&partition, sk).await?
+			}
+			K2VMonotonicRead::NonMonotonic => garage.k2v.item_table.get(&partition, sk).await?,
 		}
 		.filter(|e| K2VItemTable::matches_filter(e, &filter));
 		match item {

src/api/k2v/item.rs

@@ -5,6 +5,7 @@ use hyper::{Request, Response, StatusCode};
 
 use garage_model::k2v::causality::*;
 use garage_model::k2v::item_table::*;
+use garage_model::k2v::rpc::K2VMonotonicRead;
 
 use garage_api_common::helpers::*;
 
@@ -24,19 +25,17 @@ pub(crate) fn parse_causality_token(s: &str) -> Result<CausalContext, Error> {
 	CausalContext::parse(s).ok_or(Error::InvalidCausalityToken)
 }
 
-pub(crate) fn is_monotonic_read(req: &Request<ReqBody>) -> Result<bool, Error> {
+pub(crate) fn is_monotonic_read(req: &Request<ReqBody>) -> Result<K2VMonotonicRead, Error> {
 	let v_opt = req
 		.headers()
 		.get(X_GARAGE_NON_MONOTONIC_READ)
 		.map(|s| s.to_str())
 		.transpose()?;
 
-	// The header is set to 'true' if the read may be *non*-monotonic,
-	// and this function returns if we must do a *monotonic* read; hence
-	// the boolean negation.
 	match v_opt {
-		Some("true") => Ok(false),
+		Some("true") => Ok(K2VMonotonicRead::NonMonotonic),
-		Some("false") | None => Ok(true),
+		// Reads are monotonic by default
+		Some("false") | None => Ok(K2VMonotonicRead::Monotonic),
 		Some(s) => Err(Error::InvalidNonMonotonicRead(s.to_string())),
 	}
 }
@@ -133,14 +132,17 @@ pub async fn handle_read_item(
 		partition_key: partition_key.to_string(),
 	};
 
-	let item = if monotonic_read {
+	let item = match monotonic_read {
-		garage
+		K2VMonotonicRead::Monotonic => {
-			.k2v
+			garage
-			.item_table
+				.k2v
-			.get_monotonic(&partition_key, sort_key)
+				.item_table
-			.await?
+				.get_monotonic(&partition_key, sort_key)
-	} else {
+				.await?
-		garage.k2v.item_table.get(&partition_key, sort_key).await?
+		}
+		K2VMonotonicRead::NonMonotonic => {
+			garage.k2v.item_table.get(&partition_key, sort_key).await?
+		}
 	}
 	.ok_or(Error::NoSuchKey)?;
 

src/model/k2v/rpc.rs

@@ -38,6 +38,12 @@ const POLL_RANGE_EXTRA_DELAY: Duration = Duration::from_millis(200);
 
 const TIMESTAMP_KEY: &[u8] = b"timestamp";
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum K2VMonotonicRead {
+	Monotonic,
+	NonMonotonic,
+}
+
 /// RPC messages for K2V
 #[derive(Debug, Serialize, Deserialize)]
 enum K2VRpc {
@@ -210,7 +216,7 @@ impl K2VRpcHandler {
 		sort_key: String,
 		causal_context: CausalContext,
 		timeout_msec: u64,
-		monotonic_read: bool,
+		monotonic_read: K2VMonotonicRead,
 	) -> Result<Option<K2VItem>, Error> {
 		let poll_key = PollKey {
 			partition: K2VItemPartition {
@@ -272,7 +278,7 @@ impl K2VRpcHandler {
 		}
 
 		if let Some(v) = &resp {
-			if monotonic_read && not_all_same {
+			if monotonic_read == K2VMonotonicRead::Monotonic && not_all_same {
 				self.item_table.repair_on_read(&nodes, &[&v]).await?;
 			}
 		}
@@ -285,7 +291,7 @@ impl K2VRpcHandler {
 		range: PollRange,
 		seen_str: Option<String>,
 		timeout_msec: u64,
-		monotonic_read: bool,
+		monotonic_read: K2VMonotonicRead,
 	) -> Result<Option<(BTreeMap<String, K2VItem>, String)>, HelperError> {
 		let has_seen_marker = seen_str.is_some();
 
@@ -402,7 +408,7 @@ impl K2VRpcHandler {
 			}
 		}
 
-		if monotonic_read && !to_repair.is_empty() {
+		if monotonic_read == K2VMonotonicRead::Monotonic && !to_repair.is_empty() {
 			let to_repair: Vec<_> = to_repair
 				.into_iter()
 				.map(|k| new_items.get(&k).unwrap())