Update client_current_leader -> current_leader & add test to CI.

Updated changelog to describe the changes.

.github/workflows/ci.yaml

@@ -51,6 +51,11 @@ jobs:
         with:
           command: test
           args: -p async-raft --test compaction
+      - name: Integration Test | Current Leader
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: -p async-raft --test current_leader
       - name: Integration Test | Stepdown
         uses: actions-rs/cargo@v1
         with:

CHANGELOG.md

@@ -4,7 +4,10 @@ This changelog follows the patterns described here: https://keepachangelog.com/e
 
 ## [unreleased]
 
-## async-raft 0.6.0-alpha.2 && memstore 0.6.0-alpha.2
+## async-raft 0.6.0-alpha.2 && memstore 0.2.0-alpha.2
+### added
+- [#97](https://github.com/async-raft/async-raft/issues/97) adds the new `Raft.current_leader` method. This is a convenience method which builds upon the Raft metrics system to quickly and easily identify the current cluster leader.
+
 ### fixed
 - Fixed [#98](https://github.com/async-raft/async-raft/issues/98) where heartbeats were being passed along into the log consistency check algorithm. This had the potential to cause a Raft node to go into shutdown under some circumstances.
 - Fixed a bug where the timestamp of the last received heartbeat from a leader was not being stored, resulting in degraded cluster stability under some circumstances.

async-raft/src/raft.rs

@@ -123,12 +123,13 @@ impl<D: AppData, R: AppDataResponse, N: RaftNetwork<D>, S: RaftStorage<D, R>> Ra
         Ok(rx.await.map_err(|_| RaftError::ShuttingDown).and_then(|res| res)?)
     }
 
-    /// Get the id of the current leader from this Raft node.
+    /// Get the ID of the current leader from this Raft node.
     ///
-    /// Noted that it is the responsibility of the application to verify the leader by calling
-    /// [`client_read`] or [`client_write`].
+    /// This method is based on the Raft metrics system which does a good job at staying
+    /// up-to-date; however, the `client_read` method must still be used to guard against stale
+    /// reads. This method is perfect for making decisions on where to route client requests.
     #[tracing::instrument(level = "debug", skip(self))]
-    pub async fn client_current_leader(&self) -> Option<NodeId> {
+    pub async fn current_leader(&self) -> Option<NodeId> {
         self.metrics().borrow().current_leader
     }
 

async-raft/tests/current_leader.rs

@@ -9,16 +9,16 @@ use tokio::time::delay_for;
 
 use fixtures::RaftRouter;
 
-/// Client current leader tests.
+/// Current leader tests.
 ///
 /// What does this test do?
 ///
 /// - create a stable 3-node cluster.
-/// - call the client_current_leader interface on the all nodes, and assert success.
+/// - call the current_leader interface on the all nodes, and assert success.
 ///
-/// RUST_LOG=async_raft,memstore,client_reads=trace cargo test -p async-raft --test client_current_leader
+/// RUST_LOG=async_raft,memstore,client_reads=trace cargo test -p async-raft --test current_leader
 #[tokio::test(core_threads = 4)]
-async fn client_current_leader() -> Result<()> {
+async fn current_leader() -> Result<()> {
     fixtures::init_tracing();
 
     // Setup test dependencies.
@@ -43,7 +43,7 @@ async fn client_current_leader() -> Result<()> {
     assert_eq!(leader, 0, "expected leader to be node 0, got {}", leader);
 
     for i in 0..3 {
-        let leader = router.client_current_leader(i).await;
+        let leader = router.current_leader(i).await;
         assert_eq!(leader, Some(0), "expected leader to be node 0, got {:?}", leader);
     }
 

async-raft/tests/fixtures/mod.rs

@@ -159,10 +159,10 @@ impl RaftRouter {
     }
 
     /// Request the current leader from the target node.
-    pub async fn client_current_leader(&self, target: NodeId) -> Option<NodeId> {
+    pub async fn current_leader(&self, target: NodeId) -> Option<NodeId> {
         let rt = self.routing_table.read().await;
         let node = rt.get(&target).unwrap_or_else(|| panic!("node with ID {} does not exist", target));
-        node.0.client_current_leader().await
+        node.0.current_leader().await
     }
 
     /// Send multiple client requests to the target node, causing test failure on error.