SERVER-65254 Disable TemporarilyUnavailableExceptions by default

3 files changed, 26 insertions, 15 deletions

diff --git a/src/mongo/db/catalog/README.md b/src/mongo/db/catalog/README.md
index 3a21446485d..ddb5d479da2 100644
--- a/src/mongo/db/catalog/README.md
+++ b/src/mongo/db/catalog/README.md
@@ -406,8 +406,9 @@ See [writeConflictRetry](https://github.com/mongodb/mongo/blob/r4.4.0/src/mongo/
 
 ## TemporarilyUnavailableException
 
-A TemporarilyUnavailableException may be thrown inside the server to indicate that an operation
-cannot complete without blocking and must be retried. The storage engine may throw a
+When the server parameter `enableTemporarilyUnavailableExceptions` is enabled (off by default), a
+TemporarilyUnavailableException may be thrown inside the server to indicate that an operation cannot
+complete without blocking and must be retried. The storage engine may throw a
 TemporarilyUnavailableException (converted to a TemporarilyUnavailable error for users) when an
 operation is excessively rolled-back in the storage engine due to cache pressure or any reason that
 would prevent the operation from completing without impacting concurrent operations. The operation
diff --git a/src/mongo/db/concurrency/write_conflict_exception.idl b/src/mongo/db/concurrency/write_conflict_exception.idl
index c1ec8cb57e5..fe2206cec67 100644
--- a/src/mongo/db/concurrency/write_conflict_exception.idl
+++ b/src/mongo/db/concurrency/write_conflict_exception.idl
@@ -36,6 +36,14 @@ server_parameters:
         set_at: [ startup, runtime ]
         cpp_varname: 'WriteConflictException::trace'
 
+    enableTemporarilyUnavailableExceptions:
+        description: 'Enables the use of TemporarilyUnavailableExceptions. When disabled, reverts to
+                      throwing WriteConflictException.'
+        set_at: [ startup, runtime ]
+        cpp_varname: 'gEnableTemporarilyUnavailableExceptions'
+        cpp_vartype: AtomicWord<bool>
+        default: false
+
     temporarilyUnavailableMaxRetries:
         description: 'The number of times to retry a TemporarilyUnavailable error internally'
         set_at: [ startup, runtime ]
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
index 3605eb90a76..de31ec10751 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_util.cpp
@@ -42,6 +42,7 @@
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/db/concurrency/temporarily_unavailable_exception.h"
 #include "mongo/db/concurrency/write_conflict_exception.h"
+#include "mongo/db/concurrency/write_conflict_exception_gen.h"
 #include "mongo/db/global_settings.h"
 #include "mongo/db/server_options_general_gen.h"
 #include "mongo/db/snapshot_window_options_gen.h"
@@ -162,24 +163,25 @@ Mutex WiredTigerUtil::_tableLoggingInfoMutex =
     MONGO_MAKE_LATCH("WiredTigerUtil::_tableLoggingInfoMutex");
 WiredTigerUtil::TableLoggingInfo WiredTigerUtil::_tableLoggingInfo;
 
+bool wasRollbackReasonCachePressure(WT_SESSION* session) {
+    if (session) {
+        const auto reason = session->get_rollback_reason(session);
+        if (reason) {
+            return strncmp(WT_TXN_ROLLBACK_REASON_CACHE,
+                           reason,
+                           sizeof(WT_TXN_ROLLBACK_REASON_CACHE)) == 0;
+        }
+    }
+    return false;
+}
+
 Status wtRCToStatus_slow(int retCode, WT_SESSION* session, StringData prefix) {
     if (retCode == 0)
         return Status::OK();
 
     if (retCode == WT_ROLLBACK) {
-        const auto reasonIsCachePressure = [&] {
-            if (session) {
-                const auto reason = session->get_rollback_reason(session);
-                if (reason) {
-                    return strncmp(WT_TXN_ROLLBACK_REASON_CACHE,
-                                   reason,
-                                   sizeof(WT_TXN_ROLLBACK_REASON_CACHE)) == 0;
-                }
-            }
-            return false;
-        }();
-
-        if (reasonIsCachePressure) {
+        if (gEnableTemporarilyUnavailableExceptions.load() &&
+            wasRollbackReasonCachePressure(session)) {
             str::stream s;
             if (!prefix.empty())
                 s << prefix << " ";