fedimint_core/util/
update_merge.rs

1use futures::Future;
2use tokio::sync::Mutex;
3
4#[derive(Debug)]
5pub struct UpdateMerge {
6    last_failed: Mutex<bool>,
7}
8
9impl Default for UpdateMerge {
10    fn default() -> Self {
11        Self {
12            last_failed: Mutex::new(false),
13        }
14    }
15}
16impl UpdateMerge {
17    /// Merges concurrent futures execution.
18    ///
19    /// If two `merge` are called concurrently, the calls are merged.
20    /// But if the first call fails, the second call is still run again.
21    ///
22    /// The future `fut` is never executed concurrently.
23    pub async fn merge<E>(&self, fut: impl Future<Output = Result<(), E>>) -> Result<(), E> {
24        let mut guard = if let Ok(guard) = self.last_failed.try_lock() {
25            // not running => run now
26            guard
27        } else {
28            // already running concurrently
29            // wait for other call to return
30            let guard = self.last_failed.lock().await;
31            if *guard {
32                // Last call failed. Run again.
33                guard
34            } else {
35                // Last call completed successfully. Merge the call.
36                return Ok(());
37            }
38        };
39        // future may panic, use mark as failed initially
40        *guard = true;
41        // run the future and save last call status
42        let result = fut.await;
43        *guard = result.is_err();
44        result
45    }
46}
47
48#[cfg(test)]
49mod tests;
fedimint_core/util/update_merge.rs

fedimint_core/util/
update_merge.rs
