fixes issue where locker actions may be reordered if they fire at close enough times

patch-db/src/locker/action_mux.rs

@@ -38,7 +38,7 @@ impl ActionMux {
             _dummy_senders: vec![unlock_dummy_send, cancel_dummy_send],
         }
     }
-    pub async fn get_action(&mut self) -> Option<Action> {
+    async fn get_action(&mut self) -> Option<Action> {
         loop {
             if self.inbound_request_queue.closed
                 && self.unlock_receivers.len() == 1
@@ -68,6 +68,35 @@ impl ActionMux {
         }
     }
 
+    pub async fn get_prioritized_action_queue(&mut self) -> Vec<Action> {
+        if let Some(action) = self.get_action().await {
+            let mut actions = Vec::new();
+            // find all serviceable lock releases
+            for mut r in std::mem::take(&mut self.unlock_receivers) {
+                if let Ok(lock_info) = r.try_recv() {
+                    actions.push(Action::HandleRelease(lock_info));
+                } else {
+                    self.unlock_receivers.push(r);
+                }
+            }
+
+            // find all serviceable lock cancellations
+            for mut r in std::mem::take(&mut self.cancellation_receivers) {
+                if let Ok(lock_info) = r.try_recv() {
+                    actions.push(Action::HandleCancel(lock_info));
+                } else {
+                    self.cancellation_receivers.push(r);
+                }
+            }
+
+            // finally add the action that started it all
+            actions.push(action);
+            actions
+        } else {
+            Vec::new()
+        }
+    }
+
     pub fn push_unlock_receivers<T: IntoIterator<Item = oneshot::Receiver<LockInfo>>>(
         &mut self,
         recv: T,

patch-db/src/locker/mod.rs

@@ -28,36 +28,45 @@ impl Locker {
             let mut action_mux = ActionMux::new(receiver);
             let mut lock_server = LockBookkeeper::new();
 
-            while let Some(action) = action_mux.get_action().await {
-                #[cfg(feature = "tracing")]
-                trace!("Locker Action: {:#?}", action);
-                match action {
-                    Action::HandleRequest(mut req) => {
-                        #[cfg(feature = "tracing")]
-                        debug!("New lock request: {}", &req.lock_info);
+            loop {
+                let actions = action_mux.get_prioritized_action_queue().await;
+                if actions.is_empty() {
+                    break;
+                }
+                for action in actions {
+                    #[cfg(feature = "tracing")]
+                    trace!("Locker Action: {:#?}", action);
+                    match action {
+                        Action::HandleRequest(mut req) => {
+                            #[cfg(feature = "tracing")]
+                            debug!("New lock request: {}", &req.lock_info);
 
-                        // Pertinent Logic
-                        let req_cancel = req.cancel.take().expect("Request Cancellation Stolen");
-                        match lock_server.lease(req) {
-                            Ok(Some(recv)) => {
-                                action_mux.push_unlock_receivers(std::iter::once(recv))
+                            // Pertinent Logic
+                            let req_cancel =
+                                req.cancel.take().expect("Request Cancellation Stolen");
+                            match lock_server.lease(req) {
+                                Ok(Some(recv)) => {
+                                    action_mux.push_unlock_receivers(std::iter::once(recv))
+                                }
+                                Ok(None) => action_mux.push_cancellation_receiver(req_cancel),
+                                Err(_) => {}
                             }
-                            Ok(None) => action_mux.push_cancellation_receiver(req_cancel),
-                            Err(_) => {}
                         }
-                    }
-                    Action::HandleRelease(lock_info) => {
-                        #[cfg(feature = "tracing")]
-                        debug!("New lock release: {}", &lock_info);
+                        Action::HandleRelease(lock_info) => {
+                            #[cfg(feature = "tracing")]
+                            debug!("New lock release: {}", &lock_info);
 
-                        let new_unlock_receivers = lock_server.ret(&lock_info);
-                        action_mux.push_unlock_receivers(new_unlock_receivers);
-                    }
-                    Action::HandleCancel(lock_info) => {
-                        #[cfg(feature = "tracing")]
-                        debug!("New request canceled: {}", &lock_info);
+                            println!("Release Called {}", &lock_info);
 
-                        lock_server.cancel(&lock_info)
+                            let new_unlock_receivers = lock_server.ret(&lock_info);
+                            action_mux.push_unlock_receivers(new_unlock_receivers);
+                        }
+                        Action::HandleCancel(lock_info) => {
+                            #[cfg(feature = "tracing")]
+                            debug!("New request canceled: {}", &lock_info);
+
+                            lock_server.cancel(&lock_info)
+                        }
                     }
                 }
             }

patch-db/src/locker/order_enforcer.rs

@@ -7,6 +7,7 @@ use super::{LockError, LockInfo};
 use crate::handle::HandleId;
 use crate::LockType;
 
+#[derive(Debug, PartialEq, Eq)]
 pub(super) struct LockOrderEnforcer {
     locks_held: OrdMap<HandleId, OrdMap<(JsonPointer, LockType), usize>>,
 }

patch-db/src/locker/proptest.rs

@@ -289,6 +289,26 @@ mod tests {
         }
     }
 
+    proptest! {
+        #[test]
+        fn enforcer_lock_inverse_identity(lock_order in proptest::collection::vec(arb_lock_info(1,3), 1..30)) {
+            use crate::locker::order_enforcer::LockOrderEnforcer;
+            use rand::seq::SliceRandom;
+            let mut enforcer = LockOrderEnforcer::new();
+            for i in &lock_order {
+                enforcer.try_insert(i);
+            }
+            let mut release_order = lock_order.clone();
+            let slice: &mut [LockInfo] = &mut release_order[..];
+            slice.shuffle(&mut rand::thread_rng());
+            prop_assert!(enforcer != LockOrderEnforcer::new());
+            for i in &release_order {
+                enforcer.remove(i);
+            }
+            prop_assert_eq!(enforcer, LockOrderEnforcer::new());
+        }
+    }
+
     proptest! {
         #[test]
         fn existence_ancestors_dont_block_descendent_writes(s0 in arb_handle_id(10), s1 in arb_handle_id(10), mut ptr0 in arb_json_ptr(3), ptr1 in arb_json_ptr(3)) {

patch-db/src/test.rs

@@ -8,7 +8,7 @@ use serde_json::Value;
 use tokio::fs;
 use tokio::runtime::Builder;
 
-use crate::{self as patch_db, DbHandle};
+use crate::{self as patch_db, DbHandle, LockType};
 
 async fn init_db(db_name: String) -> PatchDb {
     cleanup_db(&db_name).await;
@@ -101,3 +101,16 @@ pub struct Child {
 
 #[derive(Debug, serde::Deserialize, serde::Serialize, HasModel)]
 pub struct NewType(Option<Box<Sample>>);
+
+#[tokio::test]
+async fn locks_dropped_from_enforcer_on_tx_save() {
+    let db = init_db("test.db".to_string()).await;
+    let mut handle = db.handle();
+    let mut tx = handle.begin().await.unwrap();
+    let ptr_a: JsonPointer = "/a".parse().unwrap();
+    let ptr_b: JsonPointer = "/b".parse().unwrap();
+    tx.lock(ptr_b, LockType::Write).await.unwrap();
+    tx.save().await.unwrap();
+    handle.lock(ptr_a, LockType::Write).await.unwrap();
+    cleanup_db("test.db").await;
+}