SERVER-17758 Move AutoGet* and Client::*Context to their own file.

The new file is mongo/db/db_raii.h.  Also, Client::Context is now OldClientContext and
Client::WriteContext is OldClientWriteContext.

1 files changed, 202 insertions, 0 deletions

diff --git a/src/mongo/db/db_raii.h b/src/mongo/db/db_raii.h
new file mode 100644
index 00000000000..580389e9b1b
--- /dev/null
+++ b/src/mongo/db/db_raii.h
@@ -0,0 +1,202 @@
+/**
+ *    Copyright (C) 2014 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 <string>
+
+#include "mongo/base/string_data.h"
+#include "mongo/db/catalog/database.h"
+#include "mongo/db/concurrency/d_concurrency.h"
+#include "mongo/db/namespace_string.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/util/timer.h"
+
+namespace mongo {
+
+    class Collection;
+
+    /**
+     * RAII-style class, which acquires a lock on the specified database in the requested mode and
+     * obtains a reference to the database. Used as a shortcut for calls to dbHolder().get().
+     *
+     * It is guaranteed that locks will be released when this object goes out of scope, therefore
+     * the database reference returned by this class should not be retained.
+     */
+    class AutoGetDb {
+        MONGO_DISALLOW_COPYING(AutoGetDb);
+    public:
+        AutoGetDb(OperationContext* txn, StringData ns, LockMode mode);
+
+        Database* getDb() const {
+            return _db;
+        }
+
+    private:
+        const Lock::DBLock _dbLock;
+        Database* const _db;
+    };
+
+    /**
+     * RAII-style class, which acquires a lock on the specified database in the requested mode and
+     * obtains a reference to the database, creating it was non-existing. Used as a shortcut for
+     * calls to dbHolder().openDb(), taking care of locking details. The requested mode must be
+     * MODE_IX or MODE_X. If the database needs to be created, the lock will automatically be
+     * reacquired as MODE_X.
+     *
+     * It is guaranteed that locks will be released when this object goes out of scope, therefore
+     * the database reference returned by this class should not be retained.
+     */
+    class AutoGetOrCreateDb {
+        MONGO_DISALLOW_COPYING(AutoGetOrCreateDb);
+    public:
+        AutoGetOrCreateDb(OperationContext* txn, StringData ns, LockMode mode);
+
+        Database* getDb() const {
+            return _db;
+        }
+
+        bool justCreated() const {
+            return _justCreated;
+        }
+
+        Lock::DBLock& lock() { return _dbLock; }
+
+    private:
+        ScopedTransaction _transaction;
+        Lock::DBLock _dbLock; // not const, as we may need to relock for implicit create
+        Database* _db;
+        bool _justCreated;
+    };
+
+    /**
+     * RAII-style class, which would acquire the appropritate hierarchy of locks for obtaining
+     * a particular collection and would retrieve a reference to the collection.
+     *
+     * It is guaranteed that locks will be released when this object goes out of scope, therefore
+     * database and collection references returned by this class should not be retained.
+     */
+    class AutoGetCollectionForRead {
+        MONGO_DISALLOW_COPYING(AutoGetCollectionForRead);
+    public:
+        AutoGetCollectionForRead(OperationContext* txn, const std::string& ns);
+        AutoGetCollectionForRead(OperationContext* txn, const NamespaceString& nss);
+        ~AutoGetCollectionForRead();
+
+        Database* getDb() const {
+            return _db.getDb();
+        }
+
+        Collection* getCollection() const {
+            return _coll;
+        }
+
+    private:
+        void _init(const std::string& ns,
+                   StringData coll);
+
+        const Timer _timer;
+        OperationContext* const _txn;
+        const ScopedTransaction _transaction;
+        const AutoGetDb _db;
+        const Lock::CollectionLock _collLock;
+
+        Collection* _coll;
+    };
+
+    /**
+     * Opens the database that we want to use and sets the appropriate namespace on the
+     * current operation.
+     */
+    class OldClientContext {
+        MONGO_DISALLOW_COPYING(OldClientContext);
+    public:
+        /** this is probably what you want */
+        OldClientContext(OperationContext* txn, const std::string& ns, bool doVersion = true);
+
+        /**
+         * Below still calls _finishInit, but assumes database has already been acquired
+         * or just created.
+         */
+        OldClientContext(OperationContext* txn,
+                         const std::string& ns,
+                         Database* db,
+                         bool justCreated);
+
+        /**
+         * note: this does not call _finishInit -- i.e., does not call
+         * ensureShardVersionOKOrThrow for example.
+         * see also: reset().
+         */
+        OldClientContext(OperationContext* txn, const std::string& ns, Database * db);
+
+        ~OldClientContext();
+
+        Database* db() const { return _db; }
+        const char* ns() const { return _ns.c_str(); }
+
+        /** @return if the db was created by this OldClientContext */
+        bool justCreated() const { return _justCreated; }
+
+    private:
+        friend class CurOp;
+        void _finishInit();
+        void _checkNotStale() const;
+
+        bool _justCreated;
+        bool _doVersion;
+        const std::string _ns;
+        Database * _db;
+        OperationContext* _txn;
+
+        Timer _timer;
+    };
+
+
+    class OldClientWriteContext {
+        MONGO_DISALLOW_COPYING(OldClientWriteContext);
+    public:
+        OldClientWriteContext(OperationContext* opCtx, const std::string& ns);
+
+        Database* db() const { return _c.db(); }
+
+        Collection* getCollection() const {
+            return _c.db()->getCollection(_nss.ns());
+        }
+
+    private:
+        OperationContext* const _txn;
+        const NamespaceString _nss;
+
+        AutoGetOrCreateDb _autodb;
+        Lock::CollectionLock _collk;
+        OldClientContext _c;
+        Collection* _collection;
+    };
+
+}  // namespace mongo