SERVER-49986 Convert isMaster command to hello and keep isMaster, ismaster aliases

(cherry picked from commit 9a4be902441496be7ef40e5404a91ac30dc81f77)

2 files changed, 13 insertions, 4 deletions

diff --git a/src/mongo/s/commands/cluster_is_master_cmd.cpp b/src/mongo/s/commands/cluster_is_master_cmd.cpp
index a71c0c28ef2..bb0fb7fec3b 100644
--- a/src/mongo/s/commands/cluster_is_master_cmd.cpp
+++ b/src/mongo/s/commands/cluster_is_master_cmd.cpp
@@ -30,6 +30,7 @@
 
 #include "mongo/platform/basic.h"
 
+#include "mongo/base/string_data.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/db/auth/sasl_mechanism_registry.h"
 #include "mongo/db/client.h"
@@ -66,9 +67,17 @@ MONGO_INITIALIZER(GenerateMongosTopologyVersion)(InitializerContext*) {
 
 namespace {
 
-class CmdIsMaster : public BasicCommandWithReplyBuilderInterface {
+constexpr auto kHelloString = "hello"_sd;
+// Aliases for the hello command in order to provide backwards compatibility.
+constexpr auto kCamelCaseIsMasterString = "isMaster"_sd;
+constexpr auto kLowerCaseIsMasterString = "ismaster"_sd;
+
+
+class CmdHello : public BasicCommandWithReplyBuilderInterface {
 public:
-    CmdIsMaster() : BasicCommandWithReplyBuilderInterface("isMaster", "ismaster") {}
+    CmdHello()
+        : BasicCommandWithReplyBuilderInterface(
+              kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -245,7 +254,7 @@ public:
         return true;
     }
 
-} isMaster;
+} hello;
 
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/s/commands/strategy.cpp b/src/mongo/s/commands/strategy.cpp
index 52c65dd69d2..b08550220d6 100644
--- a/src/mongo/s/commands/strategy.cpp
+++ b/src/mongo/s/commands/strategy.cpp
@@ -373,7 +373,7 @@ void runCommand(OperationContext* opCtx,
     opCtx->setExhaust(OpMsg::isFlagSet(m, OpMsg::kExhaustSupported));
     const auto session = opCtx->getClient()->session();
     if (session) {
-        if (!opCtx->isExhaust() || command->getName() != "isMaster"_sd) {
+        if (!opCtx->isExhaust() || command->getName() != "hello"_sd) {
             InExhaustIsMaster::get(session.get())->setInExhaustIsMaster(false);
         }
     }