Delay cosign acknowledgments

coordinator/cosign/src/delay.rs

@@ -0,0 +1,55 @@
+use core::future::Future;
+use std::time::{Duration, SystemTime};
+
+use serai_db::*;
+use serai_task::ContinuallyRan;
+
+use crate::evaluator::CosignedBlocks;
+
+/// How often callers should broadcast the cosigns flagged for rebroadcasting.
+pub const BROADCAST_FREQUENCY: Duration = Duration::from_secs(60);
+const SYNCHRONY_EXPECTATION: Duration = Duration::from_secs(10);
+const ACKNOWLEDGEMENT_DELAY: Duration =
+  Duration::from_secs(BROADCAST_FREQUENCY.as_secs() + SYNCHRONY_EXPECTATION.as_secs());
+
+create_db!(
+  SubstrateCosignDelay {
+    // The latest cosigned block number.
+    LatestCosignedBlockNumber: () -> u64,
+  }
+);
+
+/// A task to delay acknowledgement of cosigns.
+pub(crate) struct CosignDelayTask<D: Db> {
+  pub(crate) db: D,
+}
+
+impl<D: Db> ContinuallyRan for CosignDelayTask<D> {
+  fn run_iteration(&mut self) -> impl Send + Future<Output = Result<bool, String>> {
+    async move {
+      let mut made_progress = false;
+      loop {
+        let mut txn = self.db.txn();
+
+        // Receive the next block to mark as cosigned
+        let Some((block_number, time_evaluated)) = CosignedBlocks::try_recv(&mut txn) else {
+          break;
+        };
+        // Calculate when we should mark it as valid
+        let time_valid =
+          SystemTime::UNIX_EPOCH + Duration::from_secs(time_evaluated) + ACKNOWLEDGEMENT_DELAY;
+        // Sleep until then
+        tokio::time::sleep(SystemTime::now().duration_since(time_valid).unwrap_or(Duration::ZERO))
+          .await;
+
+        // Set the cosigned block
+        LatestCosignedBlockNumber::set(&mut txn, &block_number);
+        txn.commit();
+
+        made_progress = true;
+      }
+
+      Ok(made_progress)
+    }
+  }
+}