[nifi] branch main updated: NIFI-9790: This closes #5860. Fixed race condition in which SwappablePriorityQueue could attempt to access the 0th element of an empty collection

[joewitt]

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joewitt pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/nifi.git


The following commit(s) were added to refs/heads/main by this push:
     new 7ff7070  NIFI-9790: This closes #5860. Fixed race condition in which 
SwappablePriorityQueue could attempt to access the 0th element of an empty 
collection
7ff7070 is described below

commit 7ff70706ee6c9b3ea1c508701936c07bb0e6da40
Author: Mark Payne <marka...@hotmail.com>
AuthorDate: Fri Mar 11 16:28:31 2022 -0500

    NIFI-9790: This closes #5860. Fixed race condition in which 
SwappablePriorityQueue could attempt to access the 0th element of an empty 
collection
    
    Signed-off-by: Joe Witt <joew...@apache.org>
---
 .../java/org/apache/nifi/controller/queue/SwappablePriorityQueue.java   | 2 ++
 1 file changed, 2 insertions(+)

diff --git 
a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/queue/SwappablePriorityQueue.java
 
b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/queue/SwappablePriorityQueue.java
index 81e96c8..c8f2b18 100644
--- 
a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/queue/SwappablePriorityQueue.java
+++ 
b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/queue/SwappablePriorityQueue.java
@@ -460,6 +460,8 @@ public class SwappablePriorityQueue {
                     // Because we cannot obtain the write lock while already 
holding the read lock, we set a flag so that we
                     // can migrate swap to active queue only after we've 
released the read lock.
                     mustMigrateSwapToActive = true;
+                } else if (swapQueue.isEmpty()) {
+                    return FlowFileAvailability.ACTIVE_QUEUE_EMPTY;
                 } else {
                     top = swapQueue.get(0);
                 }