SERVER-51904 Add feature flag for execution control

6 files changed, 31 insertions, 17 deletions

diff --git a/src/mongo/db/storage/SConscript b/src/mongo/db/storage/SConscript
index b216260dde0..34f459b894e 100644
--- a/src/mongo/db/storage/SConscript
+++ b/src/mongo/db/storage/SConscript
@@ -196,6 +196,7 @@ env.Library(
     LIBDEPS=[
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/db/service_context',
+        '$BUILD_DIR/mongo/idl/feature_flag',
         '$BUILD_DIR/mongo/idl/server_parameter',
     ],
 )
diff --git a/src/mongo/db/storage/storage_engine_init.cpp b/src/mongo/db/storage/storage_engine_init.cpp
index f5749385ac2..7c292ac4c33 100644
--- a/src/mongo/db/storage/storage_engine_init.cpp
+++ b/src/mongo/db/storage/storage_engine_init.cpp
@@ -169,19 +169,26 @@ StorageEngine::LastShutdownState initializeStorageEngine(OperationContext* opCtx
         // TODO SERVER-64467: Remove the globalServiceContext for TicketHolders
         auto serviceContext = getGlobalServiceContext();
         auto& ticketHolders = ticketHoldersDecoration(serviceContext);
-        switch (gTicketQueueingPolicy) {
-            case QueueingPolicyEnum::Semaphore:
-                LOGV2_DEBUG(6382201, 1, "Using Semaphore-based ticketing scheduler");
-                ticketHolders.setGlobalThrottling(
-                    std::make_unique<SemaphoreTicketHolder>(readTransactions),
-                    std::make_unique<SemaphoreTicketHolder>(writeTransactions));
-                break;
-            case QueueingPolicyEnum::FifoQueue:
-                LOGV2_DEBUG(6382200, 1, "Using FIFO queue-based ticketing scheduler");
-                ticketHolders.setGlobalThrottling(
-                    std::make_unique<FifoTicketHolder>(readTransactions),
-                    std::make_unique<FifoTicketHolder>(writeTransactions));
-                break;
+        if (feature_flags::gFeatureFlagExecutionControl.isEnabledAndIgnoreFCV()) {
+            LOGV2_DEBUG(5190400, 1, "Enabling new ticketing policies");
+            switch (gTicketQueueingPolicy) {
+                case QueueingPolicyEnum::Semaphore:
+                    LOGV2_DEBUG(6382201, 1, "Using Semaphore-based ticketing scheduler");
+                    ticketHolders.setGlobalThrottling(
+                        std::make_unique<SemaphoreTicketHolder>(readTransactions),
+                        std::make_unique<SemaphoreTicketHolder>(writeTransactions));
+                    break;
+                case QueueingPolicyEnum::FifoQueue:
+                    LOGV2_DEBUG(6382200, 1, "Using FIFO queue-based ticketing scheduler");
+                    ticketHolders.setGlobalThrottling(
+                        std::make_unique<FifoTicketHolder>(readTransactions),
+                        std::make_unique<FifoTicketHolder>(writeTransactions));
+                    break;
+            }
+        } else {
+            ticketHolders.setGlobalThrottling(
+                std::make_unique<SemaphoreTicketHolder>(readTransactions),
+                std::make_unique<SemaphoreTicketHolder>(writeTransactions));
         }
     }
 
diff --git a/src/mongo/db/storage/storage_engine_parameters.cpp b/src/mongo/db/storage/storage_engine_parameters.cpp
index 729bc99ecb1..5a7a44463f8 100644
--- a/src/mongo/db/storage/storage_engine_parameters.cpp
+++ b/src/mongo/db/storage/storage_engine_parameters.cpp
@@ -33,7 +33,7 @@
 
 namespace mongo {
 
-QueueingPolicyEnum gTicketQueueingPolicy{QueueingPolicyEnum::Semaphore};
+QueueingPolicyEnum gTicketQueueingPolicy{QueueingPolicyEnum::FifoQueue};
 
 void TicketQueueingPolicy::append(OperationContext*,
                                   BSONObjBuilder& builder,
diff --git a/src/mongo/db/storage/storage_engine_parameters.idl b/src/mongo/db/storage/storage_engine_parameters.idl
index 03139a1e8bc..dcd72e5d6db 100644
--- a/src/mongo/db/storage/storage_engine_parameters.idl
+++ b/src/mongo/db/storage/storage_engine_parameters.idl
@@ -67,6 +67,12 @@ server_parameters:
     validator:
       gt: 0
 
+feature_flags:
+  featureFlagEnableExecutionControl:
+    description: Enables the new execution control queueing policy
+    cpp_varname: feature_flags::gFeatureFlagExecutionControl
+    default: false
+
 enums:
   QueueingPolicy:
     description: Queueing policy to use for obtaining tickets
diff --git a/src/mongo/util/concurrency/ticketholder.cpp b/src/mongo/util/concurrency/ticketholder.cpp
index 4043eea04b7..599c9c744e4 100644
--- a/src/mongo/util/concurrency/ticketholder.cpp
+++ b/src/mongo/util/concurrency/ticketholder.cpp
@@ -286,7 +286,7 @@ void FifoTicketHolder::release() {
     // a waiting operation to avoid leaving an operation waiting indefinitely.
     while (true) {
         if (!_queue.empty()) {
-            auto& elem = _queue.front();
+            auto elem = _queue.front();
             _enqueuedElements.subtractAndFetch(1);
             {
                 stdx::lock_guard elemLk(elem->modificationMutex);
diff --git a/src/mongo/util/concurrency/ticketholder.h b/src/mongo/util/concurrency/ticketholder.h
index 9516aa92dc7..6ea01831b87 100644
--- a/src/mongo/util/concurrency/ticketholder.h
+++ b/src/mongo/util/concurrency/ticketholder.h
@@ -157,7 +157,7 @@ private:
     void _release(WithLock);
 
     Mutex _resizeMutex =
-        MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "FifoTicketHolder::_resizeMutex");
+        MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(2), "FifoTicketHolder::_resizeMutex");
     AtomicWord<int> _capacity;
     enum class WaitingState { Waiting, Cancelled, Assigned };
     struct WaitingElement {
@@ -170,7 +170,7 @@ private:
     // _queueMutex protects all modifications made to either the _queue, or the statistics of the
     // queue.
     Mutex _queueMutex =
-        MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(0), "FifoTicketHolder::_queueMutex");
+        MONGO_MAKE_LATCH(HierarchicalAcquisitionLevel(1), "FifoTicketHolder::_queueMutex");
     AtomicWord<int> _enqueuedElements;
     AtomicWord<int> _ticketsAvailable;
 };