SERVER-28509 Downconvert document sequences when serializing requests to old protocols

6 files changed, 138 insertions, 19 deletions

diff --git a/src/mongo/db/dbmessage.h b/src/mongo/db/dbmessage.h
index 959dc59edd0..2b7f4517c72 100644
--- a/src/mongo/db/dbmessage.h
+++ b/src/mongo/db/dbmessage.h
@@ -301,7 +301,7 @@ public:
      * parses the message into the above fields
      * Warning: constructor mutates DbMessage.
      */
-    QueryMessage(DbMessage& d) {
+    explicit QueryMessage(DbMessage& d) {
         ns = d.getns();
         ntoskip = d.pullInt();
         ntoreturn = d.pullInt();
@@ -311,6 +311,14 @@ public:
         }
         queryOptions = DataView(d.msg().header().data()).read<LittleEndian<int32_t>>();
     }
+
+    /**
+     * A non-muting constructor from the whole message.
+     */
+    explicit QueryMessage(const Message& message) {
+        DbMessage dbm(message);
+        *this = QueryMessage(dbm);
+    }
 };
 
 /**
diff --git a/src/mongo/rpc/SConscript b/src/mongo/rpc/SConscript
index 3f9cbf96eae..2db964ffe9f 100644
--- a/src/mongo/rpc/SConscript
+++ b/src/mongo/rpc/SConscript
@@ -176,6 +176,7 @@ env.CppUnitTest(
         'command_reply_test.cpp',
         'command_request_builder_test.cpp',
         'command_request_test.cpp',
+        'legacy_request_test.cpp',
         'object_check_test.cpp',
         'protocol_test.cpp',
         'reply_builder_test.cpp',
diff --git a/src/mongo/rpc/command_request_builder.cpp b/src/mongo/rpc/command_request_builder.cpp
index 4a10cc7656f..9ab4e0ce2e4 100644
--- a/src/mongo/rpc/command_request_builder.cpp
+++ b/src/mongo/rpc/command_request_builder.cpp
@@ -54,8 +54,6 @@ bool fieldGoesInMetadata(StringData commandName, StringData field) {
 }  // namespace
 
 Message opCommandRequestFromOpMsgRequest(const OpMsgRequest& request) {
-    invariant(request.sequences.empty());  // Not supported yet.
-
     const auto commandName = request.getCommandName();
 
     BufBuilder builder;
@@ -88,6 +86,11 @@ Message opCommandRequestFromOpMsgRequest(const OpMsgRequest& request) {
                 bodyBuilder.append(elem);
             }
         }
+        for (auto&& seq : request.sequences) {
+            invariant(seq.name.find('.') == std::string::npos);  // Only support top-level for now.
+            dassert(!bodyBuilder.asTempObj().hasField(seq.name));
+            bodyBuilder.append(seq.name, seq.objs);
+        }
     }
     metadataBuilder.obj().appendSelfToBufBuilder(builder);
 
diff --git a/src/mongo/rpc/command_request_builder_test.cpp b/src/mongo/rpc/command_request_builder_test.cpp
index a8b3c9af8f1..e635cc5910e 100644
--- a/src/mongo/rpc/command_request_builder_test.cpp
+++ b/src/mongo/rpc/command_request_builder_test.cpp
@@ -49,27 +49,20 @@ TEST(CommandRequestBuilder, RoundTrip) {
     commandArgsBob.append(commandName, "baz");
     auto commandArgs = commandArgsBob.done();
 
-    BSONObjBuilder inputDoc1Bob{};
-    inputDoc1Bob.append("z", "t");
-    auto inputDoc1 = inputDoc1Bob.done();
+    auto request = OpMsgRequest::fromDBAndBody(databaseName, commandArgs, metadata);
+    request.sequences.push_back({"sequence", {BSON("a" << 1), BSON("b" << 2)}});
+    auto msg = rpc::opCommandRequestFromOpMsgRequest(request);
 
-    BSONObjBuilder inputDoc2Bob{};
-    inputDoc2Bob.append("h", "j");
-    auto inputDoc2 = inputDoc2Bob.done();
-
-    BSONObjBuilder inputDoc3Bob{};
-    inputDoc3Bob.append("g", "p");
-    auto inputDoc3 = inputDoc3Bob.done();
-
-    auto msg = rpc::opCommandRequestFromOpMsgRequest(
-        OpMsgRequest::fromDBAndBody(databaseName, commandArgs, metadata));
+    auto bodyAndSequence = BSONObjBuilder(commandArgs)
+                               .append("sequence", BSON_ARRAY(BSON("a" << 1) << BSON("b" << 2)))
+                               .obj();
 
     auto parsed = mongo::rpc::ParsedOpCommand::parse(msg);
 
     ASSERT_EQUALS(parsed.database, databaseName);
     ASSERT_EQUALS(StringData(parsed.body.firstElementFieldName()), commandName);
     ASSERT_BSONOBJ_EQ(parsed.metadata, metadata);
-    ASSERT_BSONOBJ_EQ(parsed.body, commandArgs);
+    ASSERT_BSONOBJ_EQ(parsed.body, bodyAndSequence);
 }
 
 TEST(CommandRequestBuilder, DownconvertSecondaryReadPreferenceToSSM) {
diff --git a/src/mongo/rpc/legacy_request_builder.cpp b/src/mongo/rpc/legacy_request_builder.cpp
index f4a9252f921..80ace2b994e 100644
--- a/src/mongo/rpc/legacy_request_builder.cpp
+++ b/src/mongo/rpc/legacy_request_builder.cpp
@@ -45,12 +45,19 @@ namespace mongo {
 namespace rpc {
 
 namespace {
+void mergeInDocumentSequences(const OpMsgRequest& request, BSONObjBuilder* body) {
+    for (auto&& seq : request.sequences) {
+        invariant(seq.name.find('.') == std::string::npos);  // Only support top-level for now.
+        dassert(!body->asTempObj().hasField(seq.name));
+        body->append(seq.name, seq.objs);
+    }
+}
+
 /**
  * Given a command request, attempts to construct a legacy command
  * object and query flags bitfield augmented with the given metadata.
  */
 BSONObj downconvertRequestBody(const OpMsgRequest& request, int* queryOptions) {
-    invariant(request.sequences.empty());  // Not supported yet.
     *queryOptions = 0;
 
     if (auto readPref = request.body["$readPreference"]) {
@@ -70,11 +77,14 @@ BSONObj downconvertRequestBody(const OpMsgRequest& request, int* queryOptions) {
                     inner.append(field);
                 }
             }
+            mergeInDocumentSequences(request, &inner);
         }
         outer.append(readPref);
         return outer.obj();
     } else {
-        return request.body.removeField("$db");  // No additional downconversion needed.
+        BSONObjBuilder body(request.body.removeField("$db"));
+        mergeInDocumentSequences(request, &body);
+        return body.obj();
     }
 }
 }  // namespace
diff --git a/src/mongo/rpc/legacy_request_test.cpp b/src/mongo/rpc/legacy_request_test.cpp
new file mode 100644
index 00000000000..2e8cacf28a3
--- /dev/null
+++ b/src/mongo/rpc/legacy_request_test.cpp
@@ -0,0 +1,104 @@
+/**
+ *    Copyright (C) 2017 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include "mongo/client/dbclientinterface.h"
+#include "mongo/db/dbmessage.h"
+#include "mongo/db/jsobj.h"
+#include "mongo/rpc/legacy_request.h"
+#include "mongo/rpc/legacy_request_builder.h"
+#include "mongo/unittest/unittest.h"
+
+namespace {
+
+using namespace mongo;
+
+TEST(LegacyRequest, RoundTrip) {
+    auto databaseName = "barbaz";
+    auto commandName = "foobar";
+
+    BSONObjBuilder metadataBob{};
+    metadataBob.append("$replData", BSONObj());
+    auto metadata = metadataBob.done();
+
+    BSONObjBuilder commandArgsBob{};
+    commandArgsBob.append(commandName, "baz");
+    auto commandArgs = commandArgsBob.done();
+
+    auto request = OpMsgRequest::fromDBAndBody(databaseName, commandArgs, metadata);
+    request.sequences.push_back({"sequence", {BSON("a" << 1), BSON("b" << 2)}});
+    auto msg = rpc::legacyRequestFromOpMsgRequest(request);
+
+    auto metadataAndSequece = BSONObjBuilder(metadata)
+                                  .append("sequence", BSON_ARRAY(BSON("a" << 1) << BSON("b" << 2)))
+                                  .obj();
+
+    auto parsed = rpc::opMsgRequestFromLegacyRequest(msg);
+    ASSERT_BSONOBJ_EQ(
+        parsed.body,
+        OpMsgRequest::fromDBAndBody(databaseName, commandArgs, metadataAndSequece).body);
+}
+
+TEST(LegacyRequestBuilder, DownconvertSecondaryReadPreference) {
+    auto readPref = BSON("mode"
+                         << "secondary");
+    auto msg = rpc::legacyRequestFromOpMsgRequest(
+        OpMsgRequest::fromDBAndBody("admin", BSON("ping" << 1 << "$readPreference" << readPref)));
+    auto parsed = QueryMessage(msg);
+
+    ASSERT_EQ(parsed.ns, "admin.$cmd"_sd);
+    ASSERT_EQ(parsed.queryOptions, QueryOption_SlaveOk);
+    ASSERT_BSONOBJ_EQ(parsed.query,
+                      fromjson("{$query: {ping: 1}, $readPreference : {mode: 'secondary'}}"));
+}
+
+TEST(CommandRequestBuilder, DownconvertExplicitPrimaryReadPreference) {
+    auto readPref = BSON("mode"
+                         << "primary");
+    auto msg = rpc::legacyRequestFromOpMsgRequest(
+        OpMsgRequest::fromDBAndBody("admin", BSON("ping" << 1 << "$readPreference" << readPref)));
+    auto parsed = QueryMessage(msg);
+
+    ASSERT_EQ(parsed.ns, "admin.$cmd"_sd);
+    ASSERT_EQ(parsed.queryOptions, 0);
+    ASSERT_BSONOBJ_EQ(parsed.query,
+                      fromjson("{$query: {ping: 1}, $readPreference : {mode: 'primary'}}"));
+}
+
+TEST(CommandRequestBuilder, DownconvertImplicitPrimaryReadPreference) {
+    auto msg =
+        rpc::legacyRequestFromOpMsgRequest(OpMsgRequest::fromDBAndBody("admin", BSON("ping" << 1)));
+    auto parsed = QueryMessage(msg);
+
+    ASSERT_EQ(parsed.ns, "admin.$cmd"_sd);
+    ASSERT_EQ(parsed.queryOptions, 0);
+    ASSERT_BSONOBJ_EQ(parsed.query, fromjson("{ping: 1}"));
+}
+
+}  // namespace