SERVER-20498 Send config server optime to shards automatically on all commands via the OP_COMMAND metadata

7 files changed, 37 insertions, 176 deletions

diff --git a/src/mongo/rpc/SConscript b/src/mongo/rpc/SConscript
index c15c4c69a68..2b171fe0ef9 100644
--- a/src/mongo/rpc/SConscript
+++ b/src/mongo/rpc/SConscript
@@ -139,8 +139,7 @@ env.Library(
     source=[
         'metadata.cpp',
         'metadata/audit_metadata.cpp',
-        'metadata/config_server_request_metadata.cpp',
-        'metadata/config_server_response_metadata.cpp',
+        'metadata/config_server_metadata.cpp',
         'metadata/server_selection_metadata.cpp',
         'metadata/sharding_metadata.cpp',
         'metadata/repl_set_metadata.cpp',
@@ -195,9 +194,9 @@ env.CppUnitTest(
 )
 
 env.CppUnitTest(
-    target='config_server_response_metadata_test',
+    target='config_server_metadata_test',
     source=[
-        'metadata/config_server_response_metadata_test.cpp',
+        'metadata/config_server_metadata_test.cpp',
     ],
     LIBDEPS=['metadata']
 )
diff --git a/src/mongo/rpc/metadata.cpp b/src/mongo/rpc/metadata.cpp
index 30b435e2872..f934e8afa2f 100644
--- a/src/mongo/rpc/metadata.cpp
+++ b/src/mongo/rpc/metadata.cpp
@@ -33,6 +33,7 @@
 #include "mongo/client/dbclientinterface.h"
 #include "mongo/db/jsobj.h"
 #include "mongo/rpc/metadata/audit_metadata.h"
+#include "mongo/rpc/metadata/config_server_metadata.h"
 #include "mongo/rpc/metadata/sharding_metadata.h"
 #include "mongo/rpc/metadata/server_selection_metadata.h"
 
@@ -56,6 +57,12 @@ Status readRequestMetadata(OperationContext* txn, const BSONObj& metadataObj) {
     }
     AuditMetadata::get(txn) = std::move(swAuditMetadata.getValue());
 
+    auto configServerMetadata = ConfigServerMetadata::readFromMetadata(metadataObj);
+    if (!configServerMetadata.isOK()) {
+        return configServerMetadata.getStatus();
+    }
+    ConfigServerMetadata::get(txn) = std::move(configServerMetadata.getValue());
+
     return Status::OK();
 }
 
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata.cpp b/src/mongo/rpc/metadata/config_server_metadata.cpp
index 14608f8d915..5119ed05c20 100644
--- a/src/mongo/rpc/metadata/config_server_response_metadata.cpp
+++ b/src/mongo/rpc/metadata/config_server_metadata.cpp
@@ -26,7 +26,7 @@
  *    it in the license file.
  */
 
-#include "mongo/rpc/metadata/config_server_response_metadata.h"
+#include "mongo/rpc/metadata/config_server_metadata.h"
 
 #include "mongo/bson/util/bson_check.h"
 #include "mongo/bson/util/bson_extract.h"
@@ -45,17 +45,19 @@ const char kOpTimeFieldName[] = "opTime";
 
 }  // unnamed namespace
 
-ConfigServerResponseMetadata::ConfigServerResponseMetadata(OpTime opTime)
-    : _opTime(std::move(opTime)) {}
+const OperationContext::Decoration<ConfigServerMetadata> ConfigServerMetadata::get =
+    OperationContext::declareDecoration<ConfigServerMetadata>();
 
-StatusWith<ConfigServerResponseMetadata> ConfigServerResponseMetadata::readFromMetadata(
+ConfigServerMetadata::ConfigServerMetadata(OpTime opTime) : _opTime(std::move(opTime)) {}
+
+StatusWith<ConfigServerMetadata> ConfigServerMetadata::readFromMetadata(
     const BSONObj& metadataObj) {
     BSONElement configMetadataElement;
 
     Status status =
         bsonExtractTypedField(metadataObj, kRootFieldName, Object, &configMetadataElement);
     if (status == ErrorCodes::NoSuchKey) {
-        return ConfigServerResponseMetadata{};
+        return ConfigServerMetadata{};
     } else if (!status.isOK()) {
         return status;
     }
@@ -68,13 +70,13 @@ StatusWith<ConfigServerResponseMetadata> ConfigServerResponseMetadata::readFromM
         return status;
     }
 
-    return ConfigServerResponseMetadata(std::move(opTime));
+    return ConfigServerMetadata(std::move(opTime));
 }
 
-void ConfigServerResponseMetadata::writeToMetadata(BSONObjBuilder* builder) const {
-    invariant(_opTime.is_initialized());
+void ConfigServerMetadata::writeToMetadata(BSONObjBuilder* builder) const {
+    invariant(_opTime);
     BSONObjBuilder configMetadataBuilder(builder->subobjStart(kRootFieldName));
-    _opTime.get().append(&configMetadataBuilder, kOpTimeFieldName);
+    _opTime->append(&configMetadataBuilder, kOpTimeFieldName);
 }
 
 }  // namespace rpc
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata.h b/src/mongo/rpc/metadata/config_server_metadata.h
index 7d96fdc663d..86eabfddf9b 100644
--- a/src/mongo/rpc/metadata/config_server_response_metadata.h
+++ b/src/mongo/rpc/metadata/config_server_metadata.h
@@ -28,6 +28,7 @@
 
 #pragma once
 
+#include "mongo/db/operation_context.h"
 #include "mongo/db/repl/optime.h"
 
 namespace mongo {
@@ -38,28 +39,31 @@ 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.
+ * This class encapsulates the metadata sent between shard mongods and mongos on every command
+ * request and response, containing metadata information about the config servers.
  *
  * format:
  * configsvr: {
  *     opTime: {ts: Timestamp(0, 0), t: 0}
  * }
  */
-class ConfigServerResponseMetadata {
+class ConfigServerMetadata {
 public:
-    ConfigServerResponseMetadata() = default;
-    explicit ConfigServerResponseMetadata(repl::OpTime opTime);
+    static const OperationContext::Decoration<ConfigServerMetadata> get;
+
+    ConfigServerMetadata() = default;
+    explicit ConfigServerMetadata(repl::OpTime opTime);
 
     /**
-     * Parses the response metadata from the given metadata object.
+     * Parses the metadata from the given metadata object.
      * Returns a non-ok status on parse error.
-     * If no metadata is found, returns a default-constructed ConfigServerResponseMetadata.
+     * If no metadata is found, returns a default-constructed ConfigServerMetadata.
      */
-    static StatusWith<ConfigServerResponseMetadata> readFromMetadata(const BSONObj& doc);
+    static StatusWith<ConfigServerMetadata> readFromMetadata(const BSONObj& doc);
 
     /**
-     * Writes the request metadata to the given BSONObjBuilder for building a command request.
+     * Writes the metadata to the given BSONObjBuilder for building a command request or response
+     * metadata.
      * Only valid to call if _opTime is initialized.
      */
     void writeToMetadata(BSONObjBuilder* builder) const;
diff --git a/src/mongo/rpc/metadata/config_server_response_metadata_test.cpp b/src/mongo/rpc/metadata/config_server_metadata_test.cpp
index 7e70749dc25..7f0a66a12d7 100644
--- a/src/mongo/rpc/metadata/config_server_response_metadata_test.cpp
+++ b/src/mongo/rpc/metadata/config_server_metadata_test.cpp
@@ -27,7 +27,7 @@
  */
 
 #include "mongo/db/jsobj.h"
-#include "mongo/rpc/metadata/config_server_response_metadata.h"
+#include "mongo/rpc/metadata/config_server_metadata.h"
 #include "mongo/unittest/unittest.h"
 
 namespace mongo {
@@ -38,7 +38,7 @@ using repl::OpTime;
 
 TEST(ConfigSvrMetadataTest, Roundtrip) {
     OpTime opTime(Timestamp(1234, 100), 5);
-    ConfigServerResponseMetadata metadata(opTime);
+    ConfigServerMetadata metadata(opTime);
 
     ASSERT_EQ(opTime, metadata.getOpTime().get());
 
@@ -52,7 +52,7 @@ TEST(ConfigSvrMetadataTest, Roundtrip) {
     BSONObj serializedObj = builder.obj();
     ASSERT_EQ(expectedObj, serializedObj);
 
-    auto cloneStatus = ConfigServerResponseMetadata::readFromMetadata(serializedObj);
+    auto cloneStatus = ConfigServerMetadata::readFromMetadata(serializedObj);
     ASSERT_OK(cloneStatus.getStatus());
 
     const auto& clonedMetadata = cloneStatus.getValue();
diff --git a/src/mongo/rpc/metadata/config_server_request_metadata.cpp b/src/mongo/rpc/metadata/config_server_request_metadata.cpp
deleted file mode 100644
index 0bdad35037f..00000000000
--- a/src/mongo/rpc/metadata/config_server_request_metadata.cpp
+++ /dev/null
@@ -1,65 +0,0 @@
-/**
- *    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_request_metadata.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 kConfigsvrOpTimeFieldName[] = "configsvrOpTime";
-}  // namespace
-
-ConfigServerRequestMetadata::ConfigServerRequestMetadata(OpTime opTime)
-    : _opTime(std::move(opTime)) {}
-
-StatusWith<ConfigServerRequestMetadata> ConfigServerRequestMetadata::readFromCommand(
-    const BSONObj& cmdObj) {
-    repl::OpTime opTime;
-    Status status = bsonExtractOpTimeField(cmdObj, kConfigsvrOpTimeFieldName, &opTime);
-    if (status == ErrorCodes::NoSuchKey) {
-        return ConfigServerRequestMetadata{};
-    } else if (!status.isOK()) {
-        return status;
-    }
-    return ConfigServerRequestMetadata(opTime);
-}
-
-void ConfigServerRequestMetadata::writeToCommand(BSONObjBuilder* builder) const {
-    invariant(_opTime.is_initialized());
-    _opTime->append(builder, kConfigsvrOpTimeFieldName);
-}
-
-}  // namespace rpc
-}  // namespace mongo
diff --git a/src/mongo/rpc/metadata/config_server_request_metadata.h b/src/mongo/rpc/metadata/config_server_request_metadata.h
deleted file mode 100644
index 33d74d7f64d..00000000000
--- a/src/mongo/rpc/metadata/config_server_request_metadata.h
+++ /dev/null
@@ -1,86 +0,0 @@
-/**
- *    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 <boost/optional.hpp>
-
-#include "mongo/db/repl/optime.h"
-
-namespace mongo {
-
-class BSONObj;
-template <typename T>
-class StatusWith;
-
-namespace rpc {
-
-/**
- * This class encapsulates the extra information that mongos may attach to commands it sends to
- * mongods, containing metadata information about the config servers.
- *
- * format:
- * configsvrOpTime: {ts: Timestamp(0, 0), t: 0}
- *
- * TODO(SERVER-20442): Currently this extracts the config server information from the main command
- * description rather than the actual OP_COMMAND metadata section.  Ideally this information
- * should be in the metadata, but we currently have no good way to add metadata to all commands
- * being *sent* to another server.
- */
-class ConfigServerRequestMetadata {
-public:
-    ConfigServerRequestMetadata() = default;
-    explicit ConfigServerRequestMetadata(repl::OpTime opTime);
-
-    /**
-     * Parses the request metadata from the given command object.
-     * Returns a non-ok status on parse error.
-     * If no metadata is found, returns a default-constructed ConfigServerRequestMetadata.
-     */
-    static StatusWith<ConfigServerRequestMetadata> readFromCommand(const BSONObj& doc);
-
-    /**
-     * Writes the request metadata to the given BSONObjBuilder for building a command request.
-     * Only valid to call if _opTime is initialized.
-     */
-    void writeToCommand(BSONObjBuilder* builder) const;
-
-    /**
-     * Returns the OpTime of the most recent operation on the config servers that this
-     * shard has seen.
-     */
-    boost::optional<repl::OpTime> getOpTime() const {
-        return _opTime;
-    }
-
-private:
-    const boost::optional<repl::OpTime> _opTime = boost::none;
-};
-
-}  // namespace rpc
-}  // namespace mongo