async persist tryout

Author: joostjager

lightning/src/util/async_persist.rs

@@ -0,0 +1,75 @@
+use ::futures::task::noop_waker;
+use futures_timer::Delay;
+use tokio::runtime::Runtime;
+use std::future::Future;
+use std::task::{Context, Poll};
+use std::time::Duration;
+
+#[derive(Debug)]
+pub enum UpdateStatus {
+    Completed,
+    InProgress,
+}
+
+// Use this boolean to control whether the store operation is async or sync.
+const ASYNC_STORE: bool = true;
+
+// Simulate an async store operation.
+async fn store() {
+    if ASYNC_STORE {
+        Delay::new(Duration::from_secs(1)).await;
+    } else {
+        std::thread::sleep(Duration::from_secs(1));
+    }
+
+    println!("Stored data...");
+}
+
+struct AsyncKVStoreWrapper {
+    runtime: Runtime,
+}
+
+impl AsyncKVStoreWrapper {
+    fn store<F>(&self, callback: F) -> UpdateStatus
+    where
+        F: FnOnce() + Send + 'static,
+    {
+        let mut fut = Box::pin(store());
+
+        let waker = noop_waker();
+        let mut cx = Context::from_waker(&waker);
+
+        match fut.as_mut().poll(&mut cx) {
+            Poll::Ready(_) => {
+                UpdateStatus::Completed
+            }
+            Poll::Pending => {
+                println!("Future not ready, using tokio runtime");
+
+                self.runtime.spawn(async move {
+                    fut.await;
+                    callback();
+                });
+
+                UpdateStatus::InProgress
+            }
+        }
+    }
+}
+
+fn main() {
+    let async_kv_store = AsyncKVStoreWrapper {
+        runtime: Runtime::new().unwrap(),
+    };
+
+    let status = async_kv_store.store(|| {
+        println!("Callback: Store operation completed!");
+
+        // Call channel_monitor_updated here.
+    });
+
+    println!("Store status: {:?}", status);
+
+    // Sleep to give async task time to complete before main exits
+    std::thread::sleep(Duration::from_secs(2));
+}