Added new routing option: SingleNodeRoutingInfo::RandomPrimary (#194)

* Added new routing option: `SingleNodeRoutingInfo::RandomPrimary`

Signed-off-by: Eran Ifrah <eifrah@amazon.com>

Author: eifrah-aws

redis/src/cluster.rs

@@ -41,14 +41,14 @@ use std::str::FromStr;
 use std::thread;
 use std::time::Duration;
 
-use rand::{seq::IteratorRandom, thread_rng, Rng};
+use rand::{seq::IteratorRandom, thread_rng};
 
 use crate::cluster_pipeline::UNROUTABLE_ERROR;
 use crate::cluster_routing::{
-    MultipleNodeRoutingInfo, ResponsePolicy, Routable, SingleNodeRoutingInfo, SlotAddr,
+    MultipleNodeRoutingInfo, ResponsePolicy, Routable, SingleNodeRoutingInfo,
 };
 use crate::cluster_slotmap::SlotMap;
-use crate::cluster_topology::{parse_and_count_slots, SLOT_SIZE};
+use crate::cluster_topology::parse_and_count_slots;
 use crate::cmd::{cmd, Cmd};
 use crate::connection::{
     connect, Connection, ConnectionAddr, ConnectionInfo, ConnectionLike, RedisConnectionInfo,
@@ -459,12 +459,9 @@ where
         };
 
         match RoutingInfo::for_routable(cmd) {
-            Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::Random)) => {
-                let mut rng = thread_rng();
-                Ok(addr_for_slot(Route::new(
-                    rng.gen_range(0..SLOT_SIZE),
-                    SlotAddr::Master,
-                ))?)
+            Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::Random))
+            | Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::RandomPrimary)) => {
+                Ok(addr_for_slot(Route::new_random_primary())?)
             }
             Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::SpecificNode(route))) => {
                 Ok(addr_for_slot(route)?)
@@ -730,6 +727,9 @@ where
                         SingleNodeRoutingInfo::SpecificNode(route) => {
                             self.get_connection(&mut connections, route)?
                         }
+                        SingleNodeRoutingInfo::RandomPrimary => {
+                            self.get_connection(&mut connections, &Route::new_random_primary())?
+                        }
                         SingleNodeRoutingInfo::ByAddress { host, port } => {
                             let address = format!("{host}:{port}");
                             let conn = self.get_connection_by_addr(&mut connections, &address)?;

redis/src/cluster_async/mod.rs

@@ -588,6 +588,9 @@ impl<C> From<SingleNodeRoutingInfo> for InternalSingleNodeRouting<C> {
             SingleNodeRoutingInfo::SpecificNode(route) => {
                 InternalSingleNodeRouting::SpecificNode(route)
             }
+            SingleNodeRoutingInfo::RandomPrimary => {
+                InternalSingleNodeRouting::SpecificNode(Route::new_random_primary())
+            }
             SingleNodeRoutingInfo::ByAddress { host, port } => {
                 InternalSingleNodeRouting::ByAddress(format!("{host}:{port}"))
             }
@@ -620,6 +623,9 @@ fn route_for_pipeline(pipeline: &crate::Pipeline) -> RedisResult<Option<Route>>
             Some(cluster_routing::RoutingInfo::SingleNode(
                 SingleNodeRoutingInfo::SpecificNode(route),
             )) => Some(route),
+            Some(cluster_routing::RoutingInfo::SingleNode(
+                SingleNodeRoutingInfo::RandomPrimary,
+            )) => Some(Route::new_random_primary()),
             Some(cluster_routing::RoutingInfo::MultiNode(_)) => None,
             Some(cluster_routing::RoutingInfo::SingleNode(SingleNodeRoutingInfo::ByAddress {
                 ..

redis/src/cluster_routing.rs

@@ -1,3 +1,4 @@
+use rand::Rng;
 use std::cmp::min;
 use std::collections::HashMap;
 
@@ -66,6 +67,8 @@ pub enum RoutingInfo {
 pub enum SingleNodeRoutingInfo {
     /// Route to any node at random
     Random,
+    /// Route to any *primary* node
+    RandomPrimary,
     /// Route to the node that matches the [Route]
     SpecificNode(Route),
     /// Route to the node with the given address.
@@ -610,7 +613,13 @@ impl RoutingInfo {
                     .and_then(|x| std::str::from_utf8(x).ok())
                     .and_then(|x| x.parse::<u64>().ok())?;
                 if key_count == 0 {
-                    Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::Random))
+                    if is_readonly_cmd(cmd) {
+                        Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::Random))
+                    } else {
+                        Some(RoutingInfo::SingleNode(
+                            SingleNodeRoutingInfo::RandomPrimary,
+                        ))
+                    }
                 } else {
                     r.arg_idx(3).map(|key| RoutingInfo::for_key(cmd, key))
                 }
@@ -949,6 +958,17 @@ impl Route {
     pub fn slot_addr(&self) -> SlotAddr {
         self.1
     }
+
+    /// Returns a new Route for a random primary node
+    pub fn new_random_primary() -> Self {
+        Self::new(random_slot(), SlotAddr::Master)
+    }
+}
+
+/// Choose a random slot from `0..SLOT_SIZE` (excluding)
+fn random_slot() -> u16 {
+    let mut rng = rand::thread_rng();
+    rng.gen_range(0..crate::cluster_topology::SLOT_SIZE)
 }
 
 #[cfg(test)]
@@ -1096,12 +1116,31 @@ mod tests {
             cmd("EVAL").arg(r#"redis.call("PING");"#).arg(0),
             cmd("EVALSHA").arg(r#"redis.call("PING");"#).arg(0),
         ] {
+            // EVAL / EVALSHA are expected to be routed to a RandomPrimary
             assert_eq!(
                 RoutingInfo::for_routable(cmd),
-                Some(RoutingInfo::SingleNode(SingleNodeRoutingInfo::Random))
+                Some(RoutingInfo::SingleNode(
+                    SingleNodeRoutingInfo::RandomPrimary
+                ))
             );
         }
 
+        // FCALL (with 0 keys) is expected to be routed to a random primary node
+        assert_eq!(
+            RoutingInfo::for_routable(cmd("FCALL").arg("foo").arg(0)),
+            Some(RoutingInfo::SingleNode(
+                SingleNodeRoutingInfo::RandomPrimary
+            ))
+        );
+
+        // While FCALL with N keys is expected to be routed to a specific node
+        assert_eq!(
+            RoutingInfo::for_routable(cmd("FCALL").arg("foo").arg(1).arg("mykey")),
+            Some(RoutingInfo::SingleNode(
+                SingleNodeRoutingInfo::SpecificNode(Route::new(slot(b"mykey"), SlotAddr::Master))
+            ))
+        );
+
         for (cmd, expected) in [
             (
                 cmd("EVAL")