SERVER-20290 Introduce migration session id

1 files changed, 83 insertions, 0 deletions

diff --git a/src/mongo/db/s/migration_session_id.h b/src/mongo/db/s/migration_session_id.h
new file mode 100644
index 00000000000..dbfde922c88
--- /dev/null
+++ b/src/mongo/db/s/migration_session_id.h
@@ -0,0 +1,83 @@
+/**
+ *    Copyright (C) 2016 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 <string>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/base/string_data.h"
+
+namespace mongo {
+
+class BSONObj;
+class BSONObjBuilder;
+template <typename T>
+class StatusWith;
+
+/**
+ * Encapsulates the logic for generating, parsing and comparing migration sessions. The migration
+ * session id is a unique identifier for a particular moveChunk command and is exchanged as part of
+ * all communication between the source and donor shards.
+ */
+class MigrationSessionId {
+public:
+    /**
+     * Constructs a new migration session identifier with the following format:
+     *  DonorId_RecipientId_UniqueIdentifier
+     */
+    static MigrationSessionId generate(StringData donor, StringData recipient);
+
+    /**
+     * Extracts the session id from BSON. If the session id is missing from the BSON contents,
+     * returns an empty MigrationSessionId.
+     */
+    static StatusWith<MigrationSessionId> extractFromBSON(const BSONObj& obj);
+
+    /**
+     * Compares two session identifiers. Two idendifiers match if either both are empty (_sessionId
+     * is not set) or if the session ids match.
+     */
+    bool matches(const MigrationSessionId& other) const;
+
+    /**
+     * Appends the migration session id to the specified builder.
+     */
+    void append(BSONObjBuilder* builder) const;
+
+    std::string toString() const;
+
+private:
+    MigrationSessionId();
+    explicit MigrationSessionId(std::string sessionId);
+
+    boost::optional<std::string> _sessionId{boost::none};
+};
+
+}  // namespace mongo