From 8b8385f99237738faf06de6ee352269569ae3473 Mon Sep 17 00:00:00 2001
From: Pavi Vetriselvan <pavithra.vetriselvan@mongodb.com>
Date: Thu, 30 Jul 2020 12:39:35 -0400
Subject: SERVER-49986 Convert isMaster command to hello and keep isMaster,
 ismaster aliases

(cherry picked from commit 9a4be902441496be7ef40e5404a91ac30dc81f77)
---
 src/mongo/db/repl/replication_info.cpp         | 13 ++++++++++---
 src/mongo/s/commands/cluster_is_master_cmd.cpp | 12 +++++++++---
 2 files changed, 19 insertions(+), 6 deletions(-)

(limited to 'src/mongo')

diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index 4007bfda120..afb68ed3314 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -33,6 +33,7 @@
 #include <list>
 #include <vector>
 
+#include "mongo/base/string_data.h"
 #include "mongo/client/connpool.h"
 #include "mongo/db/client.h"
 #include "mongo/db/commands/server_status.h"
@@ -70,6 +71,11 @@ using std::stringstream;
 namespace repl {
 namespace {
 
+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;
+
 void appendReplicationInfo(OperationContext* opCtx, BSONObjBuilder& result, int level) {
     ReplicationCoordinator* replCoord = getGlobalReplicationCoordinator();
     if (replCoord->getSettings().usingReplSets()) {
@@ -214,8 +220,10 @@ public:
     }
 } oplogInfoServerStatus;
 
-class CmdIsMaster : public BasicCommand {
+class CmdHello final : public BasicCommand {
 public:
+    CmdHello() : BasicCommand(kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
+
     bool requiresAuth() const override {
         return false;
     }
@@ -233,7 +241,6 @@ public:
     virtual void addRequiredPrivileges(const std::string& dbname,
                                        const BSONObj& cmdObj,
                                        std::vector<Privilege>* out) {}  // No auth required
-    CmdIsMaster() : BasicCommand("isMaster", "ismaster") {}
     virtual bool run(OperationContext* opCtx,
                      const string&,
                      const BSONObj& cmdObj,
@@ -403,7 +410,7 @@ public:
 
         return true;
     }
-} cmdismaster;
+} cmdhello;
 
 OpCounterServerStatusSection replOpCounterServerStatusSection("opcountersRepl", &replOpCounters);
 
diff --git a/src/mongo/s/commands/cluster_is_master_cmd.cpp b/src/mongo/s/commands/cluster_is_master_cmd.cpp
index cf5e9b81bed..d6e2c1b1187 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/db/client.h"
 #include "mongo/db/commands.h"
 #include "mongo/db/logical_session_cache.h"
@@ -48,9 +49,14 @@
 namespace mongo {
 namespace {
 
-class CmdIsMaster : public BasicCommand {
+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 BasicCommand {
 public:
-    CmdIsMaster() : BasicCommand("isMaster", "ismaster") {}
+    CmdHello() : BasicCommand(kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
 
     bool supportsWriteConcern(const BSONObj& cmd) const override {
         return false;
@@ -141,7 +147,7 @@ public:
         return true;
     }
 
-} isMaster;
+} hello;
 
 }  // namespace
 }  // namespace mongo
-- 
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