3 files changed, 24 insertions, 0 deletions
diff --git a/src/mongo/s/commands/cluster_explain_cmd.cpp b/src/mongo/s/commands/cluster_explain_cmd.cpp
index 09882eeb642..3736947d113 100644
--- a/src/mongo/s/commands/cluster_explain_cmd.cpp
+++ b/src/mongo/s/commands/cluster_explain_cmd.cpp
@@ -176,6 +176,13 @@ std::unique_ptr<CommandInvocation> ClusterExplainCmd::parse(OperationContext* op
     // arguments into the inner command since it is what is passed to the virtual
     // CommandInvocation::explain() method.
     const BSONObj explainedObj = makeExplainedObj(cmdObj, dbName);
+
+    // Extract 'comment' field from the 'explainedObj' only if there is no top-level comment.
+    auto commentField = explainedObj["comment"];
+    if (!opCtx->getComment() && commentField) {
+        opCtx->setComment(commentField.wrap());
+    }
+
     const std::string cmdName = explainedObj.firstElementFieldName();
     auto explainedCommand = CommandHelpers::findCommand(cmdName);
     uassert(ErrorCodes::CommandNotFound,
diff --git a/src/mongo/s/commands/strategy.cpp b/src/mongo/s/commands/strategy.cpp
index 5949128fe88..802a1d69ab2 100644
--- a/src/mongo/s/commands/strategy.cpp
+++ b/src/mongo/s/commands/strategy.cpp
@@ -365,6 +365,11 @@ void runCommand(OperationContext* opCtx,
     }
     opCtx->checkForInterrupt();  // May trigger maxTimeAlwaysTimeOut fail point.
 
+    // If the command includes a 'comment' field, set it on the current OpCtx.
+    if (auto commentField = request.body["comment"]) {
+        opCtx->setComment(commentField.wrap());
+    }
+
     auto invocation = command->parse(opCtx, request);
 
     // Set the logical optype, command object and namespace as soon as we identify the command. If
@@ -634,6 +639,12 @@ DbResponse Strategy::queryOp(OperationContext* opCtx, const NamespaceString& nss
     Client* const client = opCtx->getClient();
     AuthorizationSession* const authSession = AuthorizationSession::get(client);
 
+    // The legacy '$comment' operator gets converted to 'comment' by upconvertQueryEntry(). We
+    // set the comment in 'opCtx' so that it can be passed on to the respective shards.
+    if (auto commentField = upconvertedQuery["comment"]) {
+        opCtx->setComment(commentField.wrap());
+    }
+
     Status status = authSession->checkAuthForFind(nss, false);
     audit::logQueryAuthzCheck(client, nss, q.query, status.code());
     uassertStatusOK(status);
diff --git a/src/mongo/s/query/cluster_find.cpp b/src/mongo/s/query/cluster_find.cpp
index e697d32f150..69fe465d4cb 100644
--- a/src/mongo/s/query/cluster_find.cpp
+++ b/src/mongo/s/query/cluster_find.cpp
@@ -371,6 +371,12 @@ Status setUpOperationContextStateForGetMore(OperationContext* opCtx,
         ReadPreferenceSetting::get(opCtx) = *readPref;
     }
 
+    // If the originating command had a 'comment' field, we extract it and set it on opCtx. Note
+    // that if the 'getMore' command itself has a 'comment' field, we give precedence to it.
+    auto comment = cursor->getOriginatingCommand()["comment"];
+    if (!opCtx->getComment() && comment) {
+        opCtx->setComment(comment.wrap());
+    }
     if (cursor->isTailableAndAwaitData()) {
         // For tailable + awaitData cursors, the request may have indicated a maximum amount of time
         // to wait for new data. If not, default it to 1 second.  We track the deadline instead via