SERVER-51106 Make the isMaster command a derived class of hello

1 files changed, 31 insertions, 11 deletions

diff --git a/src/mongo/db/repl/replication_info.cpp b/src/mongo/db/repl/replication_info.cpp
index c65e36a8e2b..e4ad5980808 100644
--- a/src/mongo/db/repl/replication_info.cpp
+++ b/src/mongo/db/repl/replication_info.cpp
@@ -83,7 +83,6 @@ 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;
 
@@ -239,11 +238,9 @@ public:
     }
 } oplogInfoServerStatus;
 
-class CmdHello final : public BasicCommandWithReplyBuilderInterface {
+class CmdHello : public BasicCommandWithReplyBuilderInterface {
 public:
-    CmdHello()
-        : BasicCommandWithReplyBuilderInterface(
-              kHelloString, {kCamelCaseIsMasterString, kLowerCaseIsMasterString}) {}
+    CmdHello() : CmdHello(kHelloString, {}) {}
 
     const std::set<std::string>& apiVersions() const {
         return kApiVersions1;
@@ -285,11 +282,6 @@ public:
             LastError::get(opCtx->getClient()).disable();
         }
 
-        // Parse the command name, which should be one of the following: hello, isMaster, or
-        // ismaster. If the command is "hello", we must attach an "isWritablePrimary" response field
-        // instead of "ismaster" and "secondaryDelaySecs" response field instead of "slaveDelay".
-        bool useLegacyResponseFields = (cmdObj.firstElementFieldNameStringData() != kHelloString);
-
         transport::Session::TagMask sessionTagsToSet = 0;
         transport::Session::TagMask sessionTagsToUnset = 0;
 
@@ -434,7 +426,7 @@ public:
 
         auto result = replyBuilder->getBodyBuilder();
         auto currentTopologyVersion = appendReplicationInfo(
-            opCtx, &result, 0, useLegacyResponseFields, clientTopologyVersion, maxAwaitTimeMS);
+            opCtx, &result, 0, useLegacyResponseFields(), clientTopologyVersion, maxAwaitTimeMS);
 
         if (serverGlobalParams.clusterRole == ClusterRole::ConfigServer) {
             const int configServerModeNumber = 2;
@@ -506,8 +498,36 @@ public:
 
         return true;
     }
+
+protected:
+    CmdHello(const StringData cmdName, const std::initializer_list<StringData>& alias)
+        : BasicCommandWithReplyBuilderInterface(cmdName, alias) {}
+
+    virtual bool useLegacyResponseFields() {
+        return false;
+    }
+
 } cmdhello;
 
+class CmdIsMaster : public CmdHello {
+public:
+    CmdIsMaster() : CmdHello(kCamelCaseIsMasterString, {kLowerCaseIsMasterString}) {}
+
+    std::string help() const override {
+        return "Check if this server is primary for a replica set\n"
+               "{ isMaster : 1 }";
+    }
+
+protected:
+    // Parse the command name, which should be one of the following: hello, isMaster, or
+    // ismaster. If the command is "hello", we must attach an "isWritablePrimary" response field
+    // instead of "ismaster" and "secondaryDelaySecs" response field instead of "slaveDelay".
+    bool useLegacyResponseFields() override {
+        return true;
+    }
+
+} cmdIsMaster;
+
 OpCounterServerStatusSection replOpCounterServerStatusSection("opcountersRepl", &replOpCounters);
 
 }  // namespace