SERVER-21744 ElectionID always increases under PV0 and PV1.

Reset election id on PV upgrade and downgrade.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/mongo/bson/oid.cpp b/src/mongo/bson/oid.cpp
index a8ef6bb56ef..26d90d97bad 100644
--- a/src/mongo/bson/oid.cpp
+++ b/src/mongo/bson/oid.cpp
@@ -32,6 +32,7 @@
 #include "mongo/bson/oid.h"
 
 #include <boost/functional/hash.hpp>
+#include <limits>
 
 #include "mongo/base/init.h"
 #include "mongo/bson/bsonobjbuilder.h"
@@ -138,9 +139,11 @@ void OID::init() {
     setIncrement(Increment::next());
 }
 
-void OID::init(int64_t term) {
-    // each set* method handles endianness
-    setTimestamp(time(0));
+void OID::initFromTermNumber(int64_t term) {
+    // Each set* method handles endianness.
+    // Set max timestamp because the drivers compare ElectionId's to determine valid new primaries,
+    // and we want ElectionId's with terms to supercede ones without terms.
+    setTimestamp(std::numeric_limits<Timestamp>::max());
     _view().write<BigEndian<int64_t>>(term, kInstanceUniqueOffset);
 }