SERVER-19855 Make shards append last known config opTime on command metadata response

4 files changed, 227 insertions, 0 deletions

diff --git a/src/mongo/rpc/SConscript b/src/mongo/rpc/SConscript
index 075fa5a3eca..2c7617943a6 100644
--- a/src/mongo/rpc/SConscript
+++ b/src/mongo/rpc/SConscript
@@ -139,6 +139,7 @@ env.Library(
     source=[
         'metadata.cpp',
         'metadata/audit_metadata.cpp',
+        'metadata/config_server_response_metadata.cpp',
         'metadata/server_selection_metadata.cpp',
         'metadata/sharding_metadata.cpp',
         'metadata/repl_set_metadata.cpp',
@@ -192,3 +193,11 @@ env.CppUnitTest(
     LIBDEPS=['metadata']
 )
 
+env.CppUnitTest(
+    target='config_server_response_metadata_test',
+    source=[
+        'metadata/config_server_response_metadata_test.cpp',
+    ],
+    LIBDEPS=['metadata']
+)
+
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata.cpp b/src/mongo/rpc/metadata/config_server_response_metadata.cpp
new file mode 100644
index 00000000000..e47b62d8598
--- /dev/null
+++ b/src/mongo/rpc/metadata/config_server_response_metadata.cpp
@@ -0,0 +1,78 @@
+/**
+ *    Copyright (C) 2015 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/rpc/metadata/config_server_response_metadata.h"
+
+#include "mongo/bson/util/bson_check.h"
+#include "mongo/bson/util/bson_extract.h"
+#include "mongo/db/jsobj.h"
+#include "mongo/rpc/metadata.h"
+
+namespace mongo {
+namespace rpc {
+
+using repl::OpTime;
+
+namespace {
+
+const char kRootFieldName[] = "configsvr";
+const char kOpTimeFieldName[] = "opTime";
+
+}  // unnamed namespace
+
+ConfigServerResponseMetadata::ConfigServerResponseMetadata(OpTime opTime)
+    : _opTime(std::move(opTime)) {}
+
+StatusWith<ConfigServerResponseMetadata> ConfigServerResponseMetadata::readFromMetadata(
+    const BSONObj& metadataObj) {
+    BSONElement configMetadataElement;
+
+    Status status =
+        bsonExtractTypedField(metadataObj, kRootFieldName, Object, &configMetadataElement);
+    if (!status.isOK()) {
+        return status;
+    }
+
+    BSONObj configMetadataObj = configMetadataElement.Obj();
+
+    repl::OpTime opTime;
+    status = bsonExtractOpTimeField(configMetadataObj, kOpTimeFieldName, &opTime);
+    if (!status.isOK()) {
+        return status;
+    }
+
+    return ConfigServerResponseMetadata(std::move(opTime));
+}
+
+void ConfigServerResponseMetadata::writeToMetadata(BSONObjBuilder* builder) const {
+    BSONObjBuilder configMetadataBuilder(builder->subobjStart(kRootFieldName));
+    _opTime.append(&configMetadataBuilder, kOpTimeFieldName);
+}
+
+}  // namespace rpc
+}  // namespace mongo
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata.h b/src/mongo/rpc/metadata/config_server_response_metadata.h
new file mode 100644
index 00000000000..25e052c5c4b
--- /dev/null
+++ b/src/mongo/rpc/metadata/config_server_response_metadata.h
@@ -0,0 +1,70 @@
+/**
+ *    Copyright (C) 2015 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.
+ */
+
+#pragma once
+
+#include "mongo/db/repl/optime.h"
+
+namespace mongo {
+
+class BSONObj;
+class BSONObjBuilder;
+
+namespace rpc {
+
+/**
+ * This class encapsulates the response that mongod will return to mongos on every
+ * command, containing metadata information about the config servers.
+ */
+class ConfigServerResponseMetadata {
+public:
+    explicit ConfigServerResponseMetadata(repl::OpTime opTime);
+
+    /**
+     * format:
+     * configsvr: {
+     *     opTime: {ts: Timestamp(0, 0), t: 0}
+     * }
+     */
+    static StatusWith<ConfigServerResponseMetadata> readFromMetadata(const BSONObj& doc);
+    void writeToMetadata(BSONObjBuilder* builder) const;
+
+    /**
+     * Returns the OpTime of the most recent operation on the config servers that this
+     * shard has seen.
+     */
+    repl::OpTime getOpTime() const {
+        return _opTime;
+    }
+
+private:
+    repl::OpTime _opTime;
+};
+
+}  // namespace rpc
+}  // namespace mongo
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata_test.cpp b/src/mongo/rpc/metadata/config_server_response_metadata_test.cpp
new file mode 100644
index 00000000000..fcfc206b839
--- /dev/null
+++ b/src/mongo/rpc/metadata/config_server_response_metadata_test.cpp
@@ -0,0 +1,70 @@
+/**
+ *    Copyright (C) 2015 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/db/jsobj.h"
+#include "mongo/rpc/metadata/config_server_response_metadata.h"
+#include "mongo/unittest/unittest.h"
+
+namespace mongo {
+namespace rpc {
+namespace {
+
+using repl::OpTime;
+
+TEST(ConfigSvrMetadataTest, Roundtrip) {
+    OpTime opTime(Timestamp(1234, 100), 5);
+    ConfigServerResponseMetadata metadata(opTime);
+
+    ASSERT_EQ(opTime, metadata.getOpTime());
+
+    BSONObjBuilder builder;
+    metadata.writeToMetadata(&builder);
+
+    BSONObj expectedObj(
+        BSON("configsvr" << BSON(
+                 "opTime" << BSON("ts" << opTime.getTimestamp() << "t" << opTime.getTerm()))));
+
+    BSONObj serializedObj = builder.obj();
+    ASSERT_EQ(expectedObj, serializedObj);
+
+    auto cloneStatus = ConfigServerResponseMetadata::readFromMetadata(serializedObj);
+    ASSERT_OK(cloneStatus.getStatus());
+
+    const auto& clonedMetadata = cloneStatus.getValue();
+    ASSERT_EQ(opTime, clonedMetadata.getOpTime());
+
+    BSONObjBuilder clonedBuilder;
+    clonedMetadata.writeToMetadata(&clonedBuilder);
+
+    BSONObj clonedSerializedObj = clonedBuilder.obj();
+    ASSERT_EQ(expectedObj, clonedSerializedObj);
+}
+
+}  // unnamed namespace
+}  // namespace rpc
+}  // namespace mongo