SERVER-45964 Implement helper in ReplicaSetNodeProcessInterface for issuing commands to the primary

9 files changed, 38 insertions, 9 deletions

diff --git a/src/mongo/db/repl/replication_coordinator.h b/src/mongo/db/repl/replication_coordinator.h
index cd431951ca9..ef796d6877c 100644
--- a/src/mongo/db/repl/replication_coordinator.h
+++ b/src/mongo/db/repl/replication_coordinator.h
@@ -977,6 +977,13 @@ public:
      */
     virtual OpTime getLatestWriteOpTime(OperationContext* opCtx) const = 0;
 
+    /**
+     * Returns the HostAndPort of the current primary, or an empty HostAndPort if there is no
+     * primary. Note that the primary can change at any time and thus the result may be immediately
+     * stale unless run from the primary with the RSTL held.
+     */
+    virtual HostAndPort getCurrentPrimaryHostAndPort() const = 0;
+
 protected:
     ReplicationCoordinator();
 };
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 43a9eab03a2..bbbbaf3250a 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -2066,6 +2066,12 @@ OpTime ReplicationCoordinatorImpl::getLatestWriteOpTime(OperationContext* opCtx)
     return OpTime(latestOplogTimestamp, getTerm());
 }
 
+HostAndPort ReplicationCoordinatorImpl::getCurrentPrimaryHostAndPort() const {
+    stdx::lock_guard<Latch> lock(_mutex);
+    auto primary = _topCoord->getCurrentPrimaryMember();
+    return primary ? primary->getHostAndPort() : HostAndPort();
+}
+
 void ReplicationCoordinatorImpl::_killConflictingOpsOnStepUpAndStepDown(
     AutoGetRstlForStepUpStepDown* arsc, ErrorCodes::Error reason) {
     const OperationContext* rstlOpCtx = arsc->getOpCtx();
diff --git a/src/mongo/db/repl/replication_coordinator_impl.h b/src/mongo/db/repl/replication_coordinator_impl.h
index 94d0a868300..ac68f2f3d63 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.h
+++ b/src/mongo/db/repl/replication_coordinator_impl.h
@@ -349,6 +349,8 @@ public:
 
     virtual OpTime getLatestWriteOpTime(OperationContext* opCtx) const override;
 
+    virtual HostAndPort getCurrentPrimaryHostAndPort() const override;
+
     // ================== Test support API ===================
 
     /**
diff --git a/src/mongo/db/repl/replication_coordinator_mock.cpp b/src/mongo/db/repl/replication_coordinator_mock.cpp
index 22bd2968623..ef691cbcb53 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.cpp
+++ b/src/mongo/db/repl/replication_coordinator_mock.cpp
@@ -582,5 +582,9 @@ OpTime ReplicationCoordinatorMock::getLatestWriteOpTime(OperationContext* opCtx)
     return getMyLastAppliedOpTime();
 }
 
+HostAndPort ReplicationCoordinatorMock::getCurrentPrimaryHostAndPort() const {
+    return HostAndPort();
+}
+
 }  // namespace repl
 }  // namespace mongo
diff --git a/src/mongo/db/repl/replication_coordinator_mock.h b/src/mongo/db/repl/replication_coordinator_mock.h
index a5676725335..db8e460605d 100644
--- a/src/mongo/db/repl/replication_coordinator_mock.h
+++ b/src/mongo/db/repl/replication_coordinator_mock.h
@@ -331,6 +331,8 @@ public:
 
     virtual OpTime getLatestWriteOpTime(OperationContext* opCtx) const override;
 
+    virtual HostAndPort getCurrentPrimaryHostAndPort() const override;
+
 private:
     ServiceContext* const _service;
     ReplSettings _settings;
diff --git a/src/mongo/db/repl/replication_coordinator_noop.cpp b/src/mongo/db/repl/replication_coordinator_noop.cpp
index eac430b7b34..59d96c0bbfd 100644
--- a/src/mongo/db/repl/replication_coordinator_noop.cpp
+++ b/src/mongo/db/repl/replication_coordinator_noop.cpp
@@ -484,5 +484,9 @@ OpTime ReplicationCoordinatorNoOp::getLatestWriteOpTime(OperationContext* opCtx)
     return getMyLastAppliedOpTime();
 }
 
+HostAndPort ReplicationCoordinatorNoOp::getCurrentPrimaryHostAndPort() const {
+    MONGO_UNREACHABLE;
+}
+
 }  // namespace repl
 }  // namespace mongo
diff --git a/src/mongo/db/repl/replication_coordinator_noop.h b/src/mongo/db/repl/replication_coordinator_noop.h
index f0958c3a9ce..4b385d86423 100644
--- a/src/mongo/db/repl/replication_coordinator_noop.h
+++ b/src/mongo/db/repl/replication_coordinator_noop.h
@@ -268,6 +268,8 @@ public:
 
     OpTime getLatestWriteOpTime(OperationContext* opCtx) const override;
 
+    HostAndPort getCurrentPrimaryHostAndPort() const override;
+
 private:
     ServiceContext* const _service;
 };
diff --git a/src/mongo/db/repl/topology_coordinator.cpp b/src/mongo/db/repl/topology_coordinator.cpp
index fb7d8c65bd3..2b329b0f0d6 100644
--- a/src/mongo/db/repl/topology_coordinator.cpp
+++ b/src/mongo/db/repl/topology_coordinator.cpp
@@ -287,13 +287,13 @@ HostAndPort TopologyCoordinator::chooseNewSyncSource(Date_t now,
                         " not allowed and primary is unknown/down");
             _syncSource = HostAndPort();
             return _syncSource;
-        } else if (_memberIsBlacklisted(*_currentPrimaryMember(), now)) {
+        } else if (_memberIsBlacklisted(*getCurrentPrimaryMember(), now)) {
             LOGV2_DEBUG(21785,
                         1,
                         "Cannot select a sync source because chaining is not allowed and primary "
                         "member is blacklisted: {currentPrimaryMember_getHostAndPort}",
                         "currentPrimaryMember_getHostAndPort"_attr =
-                            _currentPrimaryMember()->getHostAndPort());
+                            getCurrentPrimaryMember()->getHostAndPort());
             _syncSource = HostAndPort();
             return _syncSource;
         } else if (_currentPrimaryIndex == _selfIndex) {
@@ -308,13 +308,13 @@ HostAndPort TopologyCoordinator::chooseNewSyncSource(Date_t now,
             LOG(1) << "Cannot select a sync source because chaining is not allowed and the primary "
                       "is behind me. Last oplog optime of primary {}: {}, my last fetched oplog "
                       "optime: {}"_format(
-                          _currentPrimaryMember()->getHostAndPort(),
+                          getCurrentPrimaryMember()->getHostAndPort(),
                           _memberData.at(_currentPrimaryIndex).getLastAppliedOpTime().toBSON(),
                           lastOpTimeFetched.toBSON());
             _syncSource = HostAndPort();
             return _syncSource;
         } else {
-            _syncSource = _currentPrimaryMember()->getHostAndPort();
+            _syncSource = getCurrentPrimaryMember()->getHostAndPort();
             LOGV2(21787,
                   "chaining not allowed, choosing primary as sync source candidate: {syncSource}",
                   "syncSource"_attr = _syncSource);
@@ -1542,7 +1542,7 @@ void TopologyCoordinator::setCurrentPrimary_forTest(int primaryIndex,
     }
 }
 
-const MemberConfig* TopologyCoordinator::_currentPrimaryMember() const {
+const MemberConfig* TopologyCoordinator::getCurrentPrimaryMember() const {
     if (_currentPrimaryIndex == -1)
         return nullptr;
 
@@ -1886,7 +1886,7 @@ void TopologyCoordinator::fillIsMasterForReplSet(std::shared_ptr<IsMasterRespons
     response->setIsMaster(myState.primary() && !isSteppingDown());
     response->setIsSecondary(myState.secondary());
 
-    const MemberConfig* curPrimary = _currentPrimaryMember();
+    const MemberConfig* curPrimary = getCurrentPrimaryMember();
     if (curPrimary) {
         response->setPrimary(curPrimary->getHostAndPort(horizonString));
     }
diff --git a/src/mongo/db/repl/topology_coordinator.h b/src/mongo/db/repl/topology_coordinator.h
index 7e5b0a2664c..9fa00cbc6f7 100644
--- a/src/mongo/db/repl/topology_coordinator.h
+++ b/src/mongo/db/repl/topology_coordinator.h
@@ -718,6 +718,11 @@ public:
     bool checkIfCommitQuorumCanBeSatisfied(const CommitQuorumOptions& commitQuorum,
                                            const std::vector<MemberConfig>& members) const;
 
+    /**
+     * Returns nullptr if there is no primary, or the MemberConfig* for the current primary.
+     */
+    const MemberConfig* getCurrentPrimaryMember() const;
+
     ////////////////////////////////////////////////////////////
     //
     // Test support methods
@@ -851,9 +856,6 @@ private:
      */
     MemberData* _findMemberDataByMemberId(const int memberId);
 
-    // Returns NULL if there is no primary, or the MemberConfig* for the current primary
-    const MemberConfig* _currentPrimaryMember() const;
-
     /**
      * Performs updating "_currentPrimaryIndex" for processHeartbeatResponse(), and determines if an
      * election or stepdown should commence.