SERVER-21603 Revert to old format for gleStats if being talked to by an old mongosr3.2.0-rc4

5 files changed, 15 insertions, 11 deletions

diff --git a/src/mongo/db/dbcommands.cpp b/src/mongo/db/dbcommands.cpp
index f328296e347..f73b0a186dd 100644
--- a/src/mongo/db/dbcommands.cpp
+++ b/src/mongo/db/dbcommands.cpp
@@ -1446,7 +1446,7 @@ bool Command::run(OperationContext* txn,
         // TODO: refactor out of here as part of SERVER-18326
         if (isShardingAware || serverGlobalParams.configsvr) {
             rpc::ShardingMetadata(lastOpTimeFromClient, replCoord->getElectionId())
-                .writeToMetadata(&metadataBob);
+                .writeToMetadata(&metadataBob, request.getProtocol());
         }
     }
 
diff --git a/src/mongo/rpc/legacy_reply_builder.cpp b/src/mongo/rpc/legacy_reply_builder.cpp
index 393c3bb3519..609a9483eea 100644
--- a/src/mongo/rpc/legacy_reply_builder.cpp
+++ b/src/mongo/rpc/legacy_reply_builder.cpp
@@ -100,7 +100,7 @@ LegacyReplyBuilder& LegacyReplyBuilder::setMetadata(const BSONObj& metadata) {
         // because we already have skipped some bytes for the message header.
         BSONObjBuilder resumedBuilder(
             BSONObjBuilder::ResumeBuildingTag(), _builder, sizeof(QueryResult::Value));
-        shardingMetadata.getValue().writeToMetadata(&resumedBuilder);
+        shardingMetadata.getValue().writeToMetadata(&resumedBuilder, Protocol::kOpQuery);
     }
     _state = State::kOutputDocs;
     return *this;
diff --git a/src/mongo/rpc/metadata/sharding_metadata.cpp b/src/mongo/rpc/metadata/sharding_metadata.cpp
index d04b30fb6c5..a7a926b2868 100644
--- a/src/mongo/rpc/metadata/sharding_metadata.cpp
+++ b/src/mongo/rpc/metadata/sharding_metadata.cpp
@@ -94,9 +94,11 @@ StatusWith<ShardingMetadata> ShardingMetadata::readFromMetadata(const BSONObj& m
     return ShardingMetadata(opTime, lastElectionIdElem.OID());
 }
 
-Status ShardingMetadata::writeToMetadata(BSONObjBuilder* metadataBob) const {
+Status ShardingMetadata::writeToMetadata(BSONObjBuilder* metadataBob,
+                                         rpc::Protocol protocol) const {
     BSONObjBuilder subobj(metadataBob->subobjStart(kGLEStatsFieldName));
-    if (getLastOpTime().getTerm() > repl::OpTime::kUninitializedTerm) {
+    if (getLastOpTime().getTerm() > repl::OpTime::kUninitializedTerm &&
+        protocol == Protocol::kOpCommandV1) {
         getLastOpTime().append(&subobj, kGLEStatsLastOpTimeFieldName);
     } else {
         subobj.append(kGLEStatsLastOpTimeFieldName, getLastOpTime().getTimestamp());
@@ -115,7 +117,7 @@ Status ShardingMetadata::downconvert(const BSONObj& commandReply,
         // We can reuse the same logic to write the sharding metadata out to the legacy
         // command as the element has the same format whether it is there or on the metadata
         // object.
-        swShardingMetadata.getValue().writeToMetadata(legacyCommandReplyBob);
+        swShardingMetadata.getValue().writeToMetadata(legacyCommandReplyBob, Protocol::kOpQuery);
     } else if (swShardingMetadata.getStatus() == ErrorCodes::NoSuchKey) {
         // It is valid to not have a $gleStats field.
     } else {
@@ -131,7 +133,7 @@ Status ShardingMetadata::upconvert(const BSONObj& legacyCommand,
     // as it has the same format whether it is there or on the metadata object.
     auto swShardingMetadata = readFromMetadata(legacyCommand);
     if (swShardingMetadata.isOK()) {
-        swShardingMetadata.getValue().writeToMetadata(metadataBob);
+        swShardingMetadata.getValue().writeToMetadata(metadataBob, Protocol::kOpCommandV1);
 
         // Write out the command excluding the $gleStats subobject.
         for (const auto& elem : legacyCommand) {
diff --git a/src/mongo/rpc/metadata/sharding_metadata.h b/src/mongo/rpc/metadata/sharding_metadata.h
index cf7dd0019df..9dc5fd6f9ba 100644
--- a/src/mongo/rpc/metadata/sharding_metadata.h
+++ b/src/mongo/rpc/metadata/sharding_metadata.h
@@ -29,6 +29,7 @@
 
 #include "mongo/db/jsobj.h"
 #include "mongo/db/repl/optime.h"
+#include "mongo/rpc/protocol.h"
 
 namespace mongo {
 class BSONObj;
@@ -53,8 +54,11 @@ public:
 
     /**
      * Writes ShardingMetadata to a metadata builder.
+     * If protocol is OP_QUERY, write the metadata in the old format recognizable by 3.0 mongos.
+     * TODO(SERVER-21631): Remove the 'protocol' argument and downconversion logic from this method
+     *   after 3.2 is out.
      */
-    Status writeToMetadata(BSONObjBuilder* metadataBob) const;
+    Status writeToMetadata(BSONObjBuilder* metadataBob, rpc::Protocol protocol) const;
 
     /**
      * Rewrites the ShardingMetadata from the legacy OP_QUERY format to the metadata object
diff --git a/src/mongo/rpc/metadata/sharding_metadata_test.cpp b/src/mongo/rpc/metadata/sharding_metadata_test.cpp
index 9f4fc13914e..cf76750ab94 100644
--- a/src/mongo/rpc/metadata/sharding_metadata_test.cpp
+++ b/src/mongo/rpc/metadata/sharding_metadata_test.cpp
@@ -206,10 +206,8 @@ TEST(ShardingMetadata, Downconvert) {
             BSON("$gleStats" << BSON("lastOpTime" << BSON("ts" << kLastOpTime.getTimestamp() << "t"
                                                                << kLastOpTime.getTerm())
                                                   << "electionId" << kElectionId)),
-            BSON("ok" << 1 << "$gleStats"
-                      << BSON("lastOpTime" << BSON("ts" << kLastOpTime.getTimestamp() << "t"
-                                                        << kLastOpTime.getTerm()) << "electionId"
-                                           << kElectionId)));
+            BSON("ok" << 1 << "$gleStats" << BSON("lastOpTime" << kLastOpTime.getTimestamp()
+                                                               << "electionId" << kElectionId)));
     }
     { checkDownconvert(BSON("ok" << 1), BSONObj(), BSON("ok" << 1)); }
 }