SERVER-37685 Ensure free monitoring queue preserves FIFO on messages with same deadline

1 files changed, 22 insertions, 0 deletions

diff --git a/src/mongo/db/free_mon/free_mon_queue_test.cpp b/src/mongo/db/free_mon/free_mon_queue_test.cpp
index e41b646e8df..3f181f3c720 100644
--- a/src/mongo/db/free_mon/free_mon_queue_test.cpp
+++ b/src/mongo/db/free_mon/free_mon_queue_test.cpp
@@ -115,6 +115,28 @@ TEST_F(FreeMonQueueTest, TestDeadlinePriority) {
     ASSERT(item->getType() == FreeMonMessageType::RegisterServer);
 }
 
+// Positive: Ensure deadlines sort properly when they have the same deadlines
+TEST_F(FreeMonQueueTest, TestFIFO) {
+    FreeMonMessageQueue queue;
+
+    queue.enqueue(
+        FreeMonMessage::createWithDeadline(FreeMonMessageType::RegisterServer, Date_t::min()));
+    queue.enqueue(FreeMonMessage::createWithDeadline(FreeMonMessageType::AsyncRegisterComplete,
+                                                     Date_t::min()));
+    queue.enqueue(
+        FreeMonMessage::createWithDeadline(FreeMonMessageType::RegisterCommand, Date_t::min()));
+
+    auto item = queue.dequeue(_opCtx.get()->getServiceContext()->getPreciseClockSource()).get();
+    ASSERT(item->getType() == FreeMonMessageType::RegisterServer);
+
+    item = queue.dequeue(_opCtx.get()->getServiceContext()->getPreciseClockSource()).get();
+    ASSERT(item->getType() == FreeMonMessageType::AsyncRegisterComplete);
+
+    item = queue.dequeue(_opCtx.get()->getServiceContext()->getPreciseClockSource()).get();
+    ASSERT(item->getType() == FreeMonMessageType::RegisterCommand);
+}
+
+
 // Positive: Test Queue Stop
 TEST_F(FreeMonQueueTest, TestQueueStop) {
     FreeMonMessageQueue queue;