SERVER-31456 Expose server type on Mongo connection object.

This makes it possible to prevent the  mongo shell from gossiping a
clusterTime to stand-alone mongod processes when the mongo shell is also
connected to a replica set or a sharded cluster.

8 files changed, 52 insertions, 1 deletions

diff --git a/src/mongo/client/dbclient.cpp b/src/mongo/client/dbclient.cpp
index d85032af84b..2ce3628e7de 100644
--- a/src/mongo/client/dbclient.cpp
+++ b/src/mongo/client/dbclient.cpp
@@ -861,6 +861,18 @@ Status DBClientConnection::connect(const HostAndPort& serverAddress, StringData
     }
 
     {
+        // The Server Discovery and Monitoring (SDAM) specification identifies a replica set member
+        // as either (a) having a "setName" field in the isMaster response, or (b) having
+        // "isreplicaset: true" in the isMaster response.
+        //
+        // https://github.com/mongodb/specifications/blob/c386e23724318e2fa82f4f7663d77581b755b2c3/
+        // source/server-discovery-and-monitoring/server-discovery-and-monitoring.rst#type
+        const bool hasSetNameField = swIsMasterReply.data.hasField("setName");
+        const bool isReplicaSetField = swIsMasterReply.data.getBoolField("isreplicaset");
+        _isReplicaSetMember = hasSetNameField || isReplicaSetField;
+    }
+
+    {
         std::string msgField;
         auto msgFieldExtractStatus = bsonExtractStringField(swIsMasterReply.data, "msg", &msgField);
 
diff --git a/src/mongo/client/dbclient_rs.h b/src/mongo/client/dbclient_rs.h
index 2cc259e558a..05a5e09e4a9 100644
--- a/src/mongo/client/dbclient_rs.h
+++ b/src/mongo/client/dbclient_rs.h
@@ -219,6 +219,10 @@ public:
      */
     virtual void reset();
 
+    bool isReplicaSetMember() const override {
+        return true;
+    }
+
     bool isMongos() const override {
         return false;
     }
diff --git a/src/mongo/client/dbclientinterface.h b/src/mongo/client/dbclientinterface.h
index 8c6e02f6c21..fdfc816b126 100644
--- a/src/mongo/client/dbclientinterface.h
+++ b/src/mongo/client/dbclientinterface.h
@@ -791,6 +791,8 @@ public:
 
     virtual void reset() {}
 
+    virtual bool isReplicaSetMember() const = 0;
+
     virtual bool isMongos() const = 0;
 
     /**
@@ -1047,6 +1049,10 @@ public:
             _checkConnection();
     }
 
+    bool isReplicaSetMember() const override {
+        return _isReplicaSetMember;
+    }
+
     bool isMongos() const override {
         return _isMongos;
     }
@@ -1054,6 +1060,7 @@ public:
 protected:
     int _minWireVersion{0};
     int _maxWireVersion{0};
+    bool _isReplicaSetMember = false;
     bool _isMongos = false;
 
     virtual void _auth(const BSONObj& params);
diff --git a/src/mongo/db/SConscript b/src/mongo/db/SConscript
index 73a03f0e499..5c358768737 100644
--- a/src/mongo/db/SConscript
+++ b/src/mongo/db/SConscript
@@ -552,6 +552,9 @@ env.Library(
         'curop',
         'lasterror',
     ],
+    LIBDEPS_PRIVATE=[
+        '$BUILD_DIR/mongo/db/repl/repl_coordinator_interface',
+    ],
 )
 
 env.Library(
diff --git a/src/mongo/db/dbdirectclient.cpp b/src/mongo/db/dbdirectclient.cpp
index 76f389b8434..c644f2dd631 100644
--- a/src/mongo/db/dbdirectclient.cpp
+++ b/src/mongo/db/dbdirectclient.cpp
@@ -38,6 +38,7 @@
 #include "mongo/db/commands.h"
 #include "mongo/db/curop.h"
 #include "mongo/db/operation_context.h"
+#include "mongo/db/repl/replication_coordinator.h"
 #include "mongo/db/wire_version.h"
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/transport/service_entry_point.h"
@@ -102,6 +103,11 @@ int DBDirectClient::getMaxWireVersion() {
     return WireSpec::instance().incoming.maxWireVersion;
 }
 
+bool DBDirectClient::isReplicaSetMember() const {
+    auto const* replCoord = repl::ReplicationCoordinator::get(_opCtx);
+    return replCoord && replCoord->isReplEnabled();
+}
+
 ConnectionString::ConnectionType DBDirectClient::type() const {
     return ConnectionString::MASTER;
 }
diff --git a/src/mongo/db/dbdirectclient.h b/src/mongo/db/dbdirectclient.h
index 4432d775e23..b410613cca5 100644
--- a/src/mongo/db/dbdirectclient.h
+++ b/src/mongo/db/dbdirectclient.h
@@ -97,6 +97,8 @@ public:
     int getMinWireVersion() final;
     int getMaxWireVersion() final;
 
+    bool isReplicaSetMember() const final;
+
     bool isMongos() const final {
         return false;
     }
diff --git a/src/mongo/scripting/mozjs/mongo.cpp b/src/mongo/scripting/mozjs/mongo.cpp
index 84c93aa786f..922a6931891 100644
--- a/src/mongo/scripting/mozjs/mongo.cpp
+++ b/src/mongo/scripting/mozjs/mongo.cpp
@@ -84,6 +84,9 @@ const JSFunctionSpec MongoBase::methods[] = {
         getMinWireVersion, MongoLocalInfo, MongoExternalInfo),
     MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(
         getMaxWireVersion, MongoLocalInfo, MongoExternalInfo),
+    MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(
+        isReplicaSetMember, MongoLocalInfo, MongoExternalInfo),
+    MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(isMongos, MongoLocalInfo, MongoExternalInfo),
     MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(getClusterTime, MongoLocalInfo, MongoExternalInfo),
     MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(setClusterTime, MongoLocalInfo, MongoExternalInfo),
     MONGO_ATTACH_JS_CONSTRAINED_METHOD_NO_PROTO(_startSession, MongoLocalInfo, MongoExternalInfo),
@@ -766,6 +769,18 @@ void MongoBase::Functions::getMaxWireVersion::call(JSContext* cx, JS::CallArgs a
     args.rval().setInt32(conn->getMaxWireVersion());
 }
 
+void MongoBase::Functions::isReplicaSetMember::call(JSContext* cx, JS::CallArgs args) {
+    auto conn = getConnection(args);
+
+    args.rval().setBoolean(conn->isReplicaSetMember());
+}
+
+void MongoBase::Functions::isMongos::call(JSContext* cx, JS::CallArgs args) {
+    auto conn = getConnection(args);
+
+    args.rval().setBoolean(conn->isMongos());
+}
+
 void MongoBase::Functions::getClusterTime::call(JSContext* cx, JS::CallArgs args) {
     auto ct = MongoBase::getClusterTime();
 
diff --git a/src/mongo/scripting/mozjs/mongo.h b/src/mongo/scripting/mozjs/mongo.h
index 6d8426520b3..f6c6a535c1c 100644
--- a/src/mongo/scripting/mozjs/mongo.h
+++ b/src/mongo/scripting/mozjs/mongo.h
@@ -62,12 +62,14 @@ struct MongoBase : public BaseInfo {
         MONGO_DECLARE_JS_FUNCTION(update);
         MONGO_DECLARE_JS_FUNCTION(getMinWireVersion);
         MONGO_DECLARE_JS_FUNCTION(getMaxWireVersion);
+        MONGO_DECLARE_JS_FUNCTION(isReplicaSetMember);
+        MONGO_DECLARE_JS_FUNCTION(isMongos);
         MONGO_DECLARE_JS_FUNCTION(getClusterTime);
         MONGO_DECLARE_JS_FUNCTION(setClusterTime);
         MONGO_DECLARE_JS_FUNCTION(_startSession);
     };
 
-    static const JSFunctionSpec methods[22];
+    static const JSFunctionSpec methods[24];
 
     static const char* const className;
     static const unsigned classFlags = JSCLASS_HAS_PRIVATE;