SERVER-20822 make sync source decisions based on ReplSetMetadata

3 files changed, 36 insertions, 16 deletions

diff --git a/src/mongo/rpc/metadata/repl_set_metadata.cpp b/src/mongo/rpc/metadata/repl_set_metadata.cpp
index aadd520a683..5e9a1e89f77 100644
--- a/src/mongo/rpc/metadata/repl_set_metadata.cpp
+++ b/src/mongo/rpc/metadata/repl_set_metadata.cpp
@@ -46,6 +46,7 @@ const char kLastOpCommittedFieldName[] = "lastOpCommitted";
 const char kLastOpVisibleFieldName[] = "lastOpVisible";
 const char kConfigVersionFieldName[] = "configVersion";
 const char kPrimaryIndexFieldName[] = "primaryIndex";
+const char kSyncSourceIndexFieldName[] = "syncSourceIndex";
 const char kTermFieldName[] = "term";
 
 }  // unnamed namespace
@@ -58,12 +59,14 @@ ReplSetMetadata::ReplSetMetadata(long long term,
                                  OpTime committedOpTime,
                                  OpTime visibleOpTime,
                                  long long configVersion,
-                                 int currentPrimaryIndex)
+                                 int currentPrimaryIndex,
+                                 int currentSyncSourceIndex)
     : _lastOpCommitted(std::move(committedOpTime)),
       _lastOpVisible(std::move(visibleOpTime)),
       _currentTerm(term),
       _configVersion(configVersion),
-      _currentPrimaryIndex(currentPrimaryIndex) {}
+      _currentPrimaryIndex(currentPrimaryIndex),
+      _currentSyncSourceIndex(currentSyncSourceIndex) {}
 
 StatusWith<ReplSetMetadata> ReplSetMetadata::readFromMetadata(const BSONObj& metadataObj) {
     BSONElement replMetadataElement;
@@ -84,6 +87,11 @@ StatusWith<ReplSetMetadata> ReplSetMetadata::readFromMetadata(const BSONObj& met
     if (!status.isOK())
         return status;
 
+    long long syncSourceIndex;
+    status = bsonExtractIntegerField(replMetadataObj, kSyncSourceIndexFieldName, &syncSourceIndex);
+    if (!status.isOK())
+        return status;
+
     long long term;
     status = bsonExtractIntegerField(replMetadataObj, kTermFieldName, &term);
     if (!status.isOK())
@@ -99,7 +107,8 @@ StatusWith<ReplSetMetadata> ReplSetMetadata::readFromMetadata(const BSONObj& met
     if (!status.isOK())
         return status;
 
-    return ReplSetMetadata(term, lastOpCommitted, lastOpVisible, configVersion, primaryIndex);
+    return ReplSetMetadata(
+        term, lastOpCommitted, lastOpVisible, configVersion, primaryIndex, syncSourceIndex);
 }
 
 Status ReplSetMetadata::writeToMetadata(BSONObjBuilder* builder) const {
@@ -109,6 +118,7 @@ Status ReplSetMetadata::writeToMetadata(BSONObjBuilder* builder) const {
     _lastOpVisible.append(&replMetadataBuilder, kLastOpVisibleFieldName);
     replMetadataBuilder.append(kConfigVersionFieldName, _configVersion);
     replMetadataBuilder.append(kPrimaryIndexFieldName, _currentPrimaryIndex);
+    replMetadataBuilder.append(kSyncSourceIndexFieldName, _currentSyncSourceIndex);
     replMetadataBuilder.doneFast();
 
     return Status::OK();
diff --git a/src/mongo/rpc/metadata/repl_set_metadata.h b/src/mongo/rpc/metadata/repl_set_metadata.h
index 722f3befe3e..3e80afc1f9b 100644
--- a/src/mongo/rpc/metadata/repl_set_metadata.h
+++ b/src/mongo/rpc/metadata/repl_set_metadata.h
@@ -55,16 +55,18 @@ public:
                     repl::OpTime committedOpTime,
                     repl::OpTime visibleOpTime,
                     long long configVersion,
-                    int currentPrimaryIndex);
+                    int currentPrimaryIndex,
+                    int currentSyncSourceIndex);
 
     /**
      * format:
      * {
      *     term: 0,
-     *     lastOpCommitted: {ts: Timestamp(0, 0), term: 0}
-     *     lastOpVisible: {ts: Timestamp(0, 0), term: 0}
+     *     lastOpCommitted: {ts: Timestamp(0, 0), term: 0},
+     *     lastOpVisible: {ts: Timestamp(0, 0), term: 0},
      *     configVersion: 0,
-     *     primaryIndex: 0
+     *     primaryIndex: 0,
+     *     syncSourceIndex: 0
      * }
      */
     static StatusWith<ReplSetMetadata> readFromMetadata(const BSONObj& doc);
@@ -95,11 +97,19 @@ public:
      * Returns the index of the current primary from the perspective of the sender.
      * Returns kNoPrimary if there is no primary.
      */
-    long long getPrimaryIndex() const {
+    int getPrimaryIndex() const {
         return _currentPrimaryIndex;
     }
 
     /**
+     * Returns the index of the sync source of the sender.
+     * Returns -1 if it has no sync source.
+     */
+    int getSyncSourceIndex() const {
+        return _currentSyncSourceIndex;
+    }
+
+    /**
      * Returns the current term from the perspective of the sender.
      */
     long long getTerm() const {
@@ -112,6 +122,7 @@ private:
     long long _currentTerm = -1;
     long long _configVersion = -1;
     int _currentPrimaryIndex = kNoPrimary;
+    int _currentSyncSourceIndex = -1;
 };
 
 }  // namespace rpc
diff --git a/src/mongo/rpc/metadata/repl_set_metadata_test.cpp b/src/mongo/rpc/metadata/repl_set_metadata_test.cpp
index 499bbeb0b23..68d073be8cb 100644
--- a/src/mongo/rpc/metadata/repl_set_metadata_test.cpp
+++ b/src/mongo/rpc/metadata/repl_set_metadata_test.cpp
@@ -39,7 +39,7 @@ using repl::OpTime;
 TEST(ReplResponseMetadataTest, Roundtrip) {
     OpTime opTime(Timestamp(1234, 100), 5);
     OpTime opTime2(Timestamp(7777, 100), 6);
-    ReplSetMetadata metadata(3, opTime, opTime2, 6, 12);
+    ReplSetMetadata metadata(3, opTime, opTime2, 6, 12, -1);
 
     ASSERT_EQ(opTime, metadata.getLastOpCommitted());
     ASSERT_EQ(opTime2, metadata.getLastOpVisible());
@@ -47,13 +47,12 @@ TEST(ReplResponseMetadataTest, Roundtrip) {
     BSONObjBuilder builder;
     metadata.writeToMetadata(&builder);
 
-    BSONObj expectedObj(
-        BSON(kReplSetMetadataFieldName
-             << BSON("term" << 3 << "lastOpCommitted"
-                            << BSON("ts" << opTime.getTimestamp() << "t" << opTime.getTerm())
-                            << "lastOpVisible"
-                            << BSON("ts" << opTime2.getTimestamp() << "t" << opTime2.getTerm())
-                            << "configVersion" << 6 << "primaryIndex" << 12)));
+    BSONObj expectedObj(BSON(
+        kReplSetMetadataFieldName << BSON(
+            "term" << 3 << "lastOpCommitted" << BSON("ts" << opTime.getTimestamp() << "t"
+                                                          << opTime.getTerm()) << "lastOpVisible"
+                   << BSON("ts" << opTime2.getTimestamp() << "t" << opTime2.getTerm())
+                   << "configVersion" << 6 << "primaryIndex" << 12 << "syncSourceIndex" << -1)));
 
     BSONObj serializedObj = builder.obj();
     ASSERT_EQ(expectedObj, serializedObj);