proxy: queue UNLINK command when conn terminates

proxy/src/cancellation.rs

@@ -55,6 +55,9 @@ pub enum CancelKeyOp {
     GetOld {
         key: CancelKeyData,
     },
+    Delete {
+        key: CancelKeyData,
+    },
 }
 
 impl CancelKeyOp {
@@ -64,6 +67,7 @@ impl CancelKeyOp {
             CancelKeyOp::Refresh { .. } => RedisMsgKind::Expire,
             CancelKeyOp::Get { .. } => RedisMsgKind::Get,
             CancelKeyOp::GetOld { .. } => RedisMsgKind::HGet,
+            CancelKeyOp::Delete { .. } => RedisMsgKind::Unlink,
         }
     }
 
@@ -128,6 +132,10 @@ impl Pipeline {
         self.inner.add_command(cmd);
         self.replies += 1;
     }
+
+    fn add_command_ignore_reply(&mut self, cmd: Cmd) {
+        self.inner.add_command(cmd).ignore();
+    }
 }
 
 impl CancelKeyOp {
@@ -153,6 +161,10 @@ impl CancelKeyOp {
                 let key = KeyPrefix::Cancel(*key).build_redis_key();
                 pipe.add_command(Cmd::get(key));
             }
+            CancelKeyOp::Delete { key } => {
+                let key = KeyPrefix::Cancel(*key).build_redis_key();
+                pipe.add_command_ignore_reply(Cmd::unlink(key));
+            }
         }
     }
 }
@@ -497,9 +509,11 @@ impl Session {
 
         let mut cancel = pin!(cancel);
 
+        #[derive(Copy, Clone, PartialEq, Eq)]
         enum State {
             Set,
             Refresh,
+            Delete,
         }
         let mut state = State::Set;
 
@@ -529,9 +543,23 @@ impl Session {
                         expire: CANCEL_KEY_TTL,
                     }
                 }
+
+                State::Delete => {
+                    tracing::debug!(
+                        src=%self.key,
+                        dest=?cancel_closure.cancel_token,
+                        "deleting cancellation key"
+                    );
+                    CancelKeyOp::Delete { key: self.key }
+                }
             };
 
             let (id, rx) = tx.enqueue((op.metric_guard(), op));
+            if state == State::Delete {
+                // The key deletion is just best effort. We enqueue the command,
+                // but don't drive the queue and wait for a response.
+                break;
+            }
 
             match tx.call(id, rx, cancel.as_mut()).await {
                 // SET returns OK
@@ -568,7 +596,10 @@ impl Session {
                     continue;
                 }
 
-                Err(BatchQueueError::Cancelled(Err(_cancelled))) => break,
+                Err(BatchQueueError::Cancelled(Err(_cancelled))) => {
+                    state = State::Delete;
+                    continue;
+                }
             }
 
             // wait before continuing. break immediately if cancelled.
@@ -576,7 +607,7 @@ impl Session {
                 .await
                 .is_err()
             {
-                break;
+                state = State::Delete;
             }
         }
 

proxy/src/metrics.rs

@@ -378,6 +378,7 @@ pub enum RedisMsgKind {
     Get,
     Expire,
     HGet,
+    Unlink,
 }
 
 #[derive(Default, Clone)]