add check to shared references to nodes before deletion

Author: zhao-lang

cmd.sh

@@ -17,7 +17,7 @@ redis-cli hnsw.search test1 5 ${data}
 for i in {1..100}
 do
 redis-cli hnsw.node.del test1 node${i-1}
-sleep 0.001
+sleep 0.1
 done
 
 redis-cli hnsw.del test1

src/hnsw/hnsw_tests.rs

@@ -15,10 +15,7 @@ fn hnsw_test() {
     assert_eq!(index.max_layer, 0);
     assert_eq!(index.enterpoint, None);
 
-    let mock_fn = |_s: String, _n: Node<f32>| {
-        let ten_millis = time::Duration::from_millis(10);
-        thread::sleep(ten_millis);
-    };
+    let mock_fn = |_s: String, _n: Node<f32>| {};
 
     // add node
     for i in 0..100 {
@@ -27,8 +24,8 @@ fn hnsw_test() {
         index.add_node(&name, &data, mock_fn).unwrap();
     }
     // sleep for a brief period to make sure all threads are done
-    let hundred_millis = time::Duration::from_millis(100);
-    thread::sleep(hundred_millis);
+    let ten_millis = time::Duration::from_millis(10);
+    thread::sleep(ten_millis);
     for i in 0..100 {
         let node_name = format!("node{}", i);
         let node = index.nodes.get(&node_name).unwrap();
@@ -70,8 +67,8 @@ fn hnsw_test() {
             }
         }
         // sleep for a brief period to make sure all threads are done
-        let hundred_millis = time::Duration::from_millis(10);
-        thread::sleep(hundred_millis);
+        let ten_millis = time::Duration::from_millis(10);
+        thread::sleep(ten_millis);
         let sc = Arc::strong_count(&node.0);
         if sc > 1 {
             println!("Delete {:?}", node);

src/lib.rs

@@ -293,6 +293,14 @@ fn delete_node(ctx: &Context, args: Vec<String>) -> RedisResult {
     let node_name = format!("{}.{}.{}", PREFIX, &args[1], &args[2]);
 
     // TODO return error if node has more than 1 strong_count
+    let node = index.nodes.get(&node_name).unwrap();
+    if Arc::strong_count(&node.0) > 1 {
+        return Err(format!(
+            "{} is being accessed, unable to delete. Try again later",
+            &node_name
+        )
+        .into());
+    }
     match index.delete_node(&node_name, update_node) {
         Err(e) => return Err(e.error_string().into()),
         _ => (),