feat: update basic example with a more simple acquire and run function

crates/noleader/examples/basic/main.rs

@@ -23,28 +23,21 @@ async fn main() -> anyhow::Result<()> {
     tracing::info!("creating bucket");
     leader.create_bucket().await?;
 
-    tokio::spawn({
-        let leader = leader.clone();
-        let leader_id = leader_id.clone();
-
-        async move {
-            tracing::debug!(leader_id, "starting leader");
-            leader
-                .start(CancellationToken::default())
-                .await
-                .expect("to succeed");
-        }
-    });
-
     leader
-        .do_while_leader(move |token| async move {
-            loop {
-                if token.is_cancelled() {
-                    return Ok(());
-                }
+        .acquire_and_run({
+            move |token| {
+                let leader_id = leader_id.clone();
 
-                tracing::info!("do work as leader");
-                tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+                async move {
+                    loop {
+                        if token.is_cancelled() {
+                            return Ok(());
+                        }
+
+                        tracing::info!(leader_id, "do work as leader");
+                        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
+                    }
+                }
             }
         })
         .await?;

crates/noleader/src/lib.rs

@@ -31,19 +31,72 @@ impl Leader {
         }
     }
 
+    pub async fn acquire_and_run<F, Fut>(&self, f: F) -> anyhow::Result<()>
+    where
+        F: Fn(CancellationToken) -> Fut,
+        Fut: Future<Output = anyhow::Result<()>> + Send + 'static,
+    {
+        let parent_token = CancellationToken::default();
+        let s = self.clone();
+
+        let server_token = parent_token.child_token();
+
+        // Start the server election process in another task, this is because start is blocking
+        let handle = tokio::spawn({
+            let server_token = server_token.child_token();
+            async move {
+                match s.start(server_token).await {
+                    Ok(_) => {}
+                    Err(e) => tracing::error!("leader election process failed: {}", e),
+                }
+
+                tracing::info!("shutting down noleader");
+
+                parent_token.cancel();
+            }
+        });
+
+        // Do the work if we're leader
+        let res = self
+            .do_while_leader_inner(server_token.child_token(), f)
+            .await;
+
+        // Stop the server election process if our provided functions returns an error;
+        server_token.cancel();
+        // Close down the task as well, it should already be stopped, but this forces the task to close
+        handle.abort();
+        res?;
+
+        Ok(())
+    }
+
     pub async fn do_while_leader<F, Fut>(&self, f: F) -> anyhow::Result<()>
+    where
+        F: Fn(CancellationToken) -> Fut,
+        Fut: Future<Output = anyhow::Result<()>> + Send + 'static,
+    {
+        self.do_while_leader_inner(CancellationToken::new(), f)
+            .await
+    }
+
+    async fn do_while_leader_inner<F, Fut>(
+        &self,
+        cancellation_token: CancellationToken,
+        f: F,
+    ) -> anyhow::Result<()>
     where
         F: Fn(CancellationToken) -> Fut,
         Fut: Future<Output = anyhow::Result<()>> + Send + 'static,
     {
         loop {
+            let cancellation_token = cancellation_token.child_token();
+
             let is_leader = self.is_leader.clone();
             if !is_leader.load(Ordering::Relaxed) {
                 tokio::time::sleep(Duration::from_secs(1)).await;
                 continue;
             }
 
-            let cancellation_token = CancellationToken::new();
             let child_token = cancellation_token.child_token();
 
             let guard = tokio::spawn(async move {