SERVER-62283 stop gap measure to prevent underflow asserting

(cherry picked from commit c87e167ecf9616be6a5878411b87faade3f2ac31)

2 files changed, 22 insertions, 8 deletions

diff --git a/src/mongo/db/pipeline/memory_usage_tracker.h b/src/mongo/db/pipeline/memory_usage_tracker.h
index 8bf1e6437c6..275183081ef 100644
--- a/src/mongo/db/pipeline/memory_usage_tracker.h
+++ b/src/mongo/db/pipeline/memory_usage_tracker.h
@@ -29,6 +29,7 @@
 
 #pragma once
 
+#include <algorithm>
 #include <memory>
 #include <utility>
 
@@ -49,11 +50,20 @@ public:
         PerFunctionMemoryTracker() = delete;
 
         void update(long long diff) {
-            tassert(5578603,
-                    str::stream() << "Underflow on memory tracking, attempting to add " << diff
-                                  << " but only " << _currentMemoryBytes << " available",
-                    diff >= 0 || _currentMemoryBytes >= std::abs(diff));
-            set(_currentMemoryBytes + diff);
+
+            // TODO SERVER-61281: this is a temporary measure in tackling the problem in this
+            // ticket. It prevents the underflow from happening but doesn't address the cause
+            // which is inaccurate tracking.
+            // Once inaccurate tracking is resolved, the underflow assertion below could be
+            // restored.
+            //      tassert(5578603,
+            //              str::stream() << "Underflow on memory tracking, attempting to add " <<
+            //              diff
+            //                            << " but only " << _currentMemoryBytes << " available",
+            //              diff >= 0 || _currentMemoryBytes >= std::abs(diff));
+            //      set(_currentMemoryBytes + diff);
+
+            set(std::max(_currentMemoryBytes + diff, 0LL));
         }
 
         void set(long long total) {
diff --git a/src/mongo/db/pipeline/memory_usage_tracker_test.cpp b/src/mongo/db/pipeline/memory_usage_tracker_test.cpp
index f0514d86758..cc354e7fd69 100644
--- a/src/mongo/db/pipeline/memory_usage_tracker_test.cpp
+++ b/src/mongo/db/pipeline/memory_usage_tracker_test.cpp
@@ -109,14 +109,18 @@ DEATH_TEST_F(MemoryUsageTrackerTest,
     _tracker.update(-100);
 }
 
-DEATH_TEST_F(MemoryUsageTrackerTest,
-             UpdateFunctionUsageToNegativeIsDisallowed,
-             "Underflow on memory tracking") {
+TEST_F(MemoryUsageTrackerTest, UpdateFunctionUsageToNegativeIsDisallowed) {
     _funcTracker.set(50LL);
     ASSERT_EQ(_tracker.currentMemoryBytes(), 50LL);
     ASSERT_EQ(_tracker.maxMemoryBytes(), 50LL);
 
+    // TODO SERVER-61281: Temporarily disable the assert (and associated test) in
+    // PerFunctionMemoryTracker.update() to prevent inaccurate tracking to cause underflow errors
+    // Once accurate tracking is implemented and no underflow should happen, this negative test
+    // could be restored to verify that "Underflow on memory tracking" is reported.
+
     _funcTracker.update(-100);
+    ASSERT_EQ(_tracker.currentMemoryBytes(), 0LL);
 }
 
 }  // namespace