fix: re-enable test_scheduler_drop_idle by resolving race condition

unified-scheduler-pool/src/lib.rs

@@ -2869,10 +2869,8 @@ mod tests {
     }
 
     const SHORTENED_POOL_CLEANER_INTERVAL: Duration = Duration::from_millis(1);
-    const SHORTENED_MAX_POOLING_DURATION: Duration = Duration::from_millis(100);
 
     #[test]
-    #[ignore]
     fn test_scheduler_drop_idle() {
         agave_logger::setup();
 
@@ -2883,6 +2881,15 @@ mod tests {
             &TestCheckPoint::AfterIdleSchedulerCleaned,
         ]);
 
+        // Use 300ms pooling duration as a balance between:
+        // - Keeping the test fast (as small as possible)
+        // - Providing a large enough window to avoid the race condition where the second
+        //   scheduler could also be freed before we can assert only one remains
+        const TEST_MAX_POOLING_DURATION_MS: u64 = 300;
+        const TEST_MAX_POOLING_DURATION: Duration =
+            Duration::from_millis(TEST_MAX_POOLING_DURATION_MS);
+        const TEST_WAIT_FOR_IDLE_MS: u64 = TEST_MAX_POOLING_DURATION_MS + 200;
+        const TEST_WAIT_FOR_IDLE: Duration = Duration::from_millis(TEST_WAIT_FOR_IDLE_MS);
         let ignored_prioritization_fee_cache = Arc::new(PrioritizationFeeCache::new(0u64));
         let pool_raw = DefaultSchedulerPool::do_new(
             None,
@@ -2891,7 +2898,7 @@ mod tests {
             None,
             ignored_prioritization_fee_cache,
             SHORTENED_POOL_CLEANER_INTERVAL,
-            SHORTENED_MAX_POOLING_DURATION,
+            TEST_MAX_POOLING_DURATION,
             DEFAULT_MAX_USAGE_QUEUE_COUNT,
             DEFAULT_TIMEOUT_DURATION,
         );
@@ -2905,8 +2912,9 @@ mod tests {
         let new_scheduler_id = new_scheduler.id();
         Box::new(old_scheduler.into_inner().1).return_to_pool();
 
-        // sleepless_testing can't be used; wait a bit here to see real progress of wall time...
-        sleep(SHORTENED_MAX_POOLING_DURATION * 10);
+        // Wait for old_scheduler to be considered idle by the cleaner.
+        sleep(TEST_WAIT_FOR_IDLE);
+
         Box::new(new_scheduler.into_inner().1).return_to_pool();
 
         // Block solScCleaner until we see returned schedlers...
@@ -2916,12 +2924,8 @@ mod tests {
         // See the old (= idle) scheduler gone only after solScCleaner did its job...
         sleepless_testing::at(&TestCheckPoint::AfterIdleSchedulerCleaned);
 
-        // The following assertion is racy.
-        //
-        // We need to make sure new_scheduler isn't treated as idle up to now since being returned
-        // to the pool after sleep(SHORTENED_MAX_POOLING_DURATION * 10).
-        // Removing only old_scheduler is the expected behavior. So, make
-        // SHORTENED_MAX_POOLING_DURATION rather long...
+        // Only new_scheduler should remain. old_scheduler exceeds the
+        // TEST_MAX_POOLING_DURATION idle threshold, while new_scheduler does not.
         assert_eq!(pool_raw.scheduler_inners.lock().unwrap().len(), 1);
         assert_eq!(
             pool_raw
@@ -3012,6 +3016,7 @@ mod tests {
 
     #[test]
     fn test_scheduler_drop_stale() {
+        const SHORTENED_MAX_POOLING_DURATION: Duration = Duration::from_millis(100);
         agave_logger::setup();
 
         let _progress = sleepless_testing::setup(&[