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/**
* 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/storage/mmap_v1/dur_recovery_unit.h"
#include <algorithm>
#include <string>
#include "mongo/db/operation_context.h"
#include "mongo/db/storage/mmap_v1/dur.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/log.h"
// Remove once we are ready to enable
#define ROLLBACK_ENABLED 0
namespace mongo {
/**
* A MemoryWrite provides rollback by keeping a pre-image.
*/
class MemoryWrite : public RecoveryUnit::Change {
public:
MemoryWrite(char* base, size_t len) : _base(base), _preimage(base, len) { }
virtual void commit();
virtual void rollback();
private:
char* _base;
std::string _preimage; // TODO consider storing out-of-line
};
DurRecoveryUnit::DurRecoveryUnit(OperationContext* txn)
: _txn(txn),
_mustRollback(false)
{}
void DurRecoveryUnit::beginUnitOfWork() {
#if ROLLBACK_ENABLED
_startOfUncommittedChangesForLevel.push_back(_changes.size());
#endif
}
void DurRecoveryUnit::commitUnitOfWork() {
#if ROLLBACK_ENABLED
invariant(inAUnitOfWork());
invariant(!_mustRollback);
if (!inOutermostUnitOfWork()) {
// If we are nested, make all changes for this level part of the containing UnitOfWork.
// They will be added to the global damages list once the outermost UnitOfWork commits,
// which it must now do.
if (haveUncommitedChangesAtCurrentLevel()) {
_startOfUncommittedChangesForLevel.back() = _changes.size();
}
return;
}
publishChanges();
#endif
// global journal flush opportunity
getDur().commitIfNeeded(_txn);
}
void DurRecoveryUnit::endUnitOfWork() {
#if ROLLBACK_ENABLED
invariant(inAUnitOfWork());
if (haveUncommitedChangesAtCurrentLevel()) {
rollbackInnermostChanges();
}
_startOfUncommittedChangesForLevel.pop_back();
#endif
}
void DurRecoveryUnit::publishChanges() {
if (!inAUnitOfWork())
return;
invariant(!_mustRollback);
invariant(inOutermostUnitOfWork());
for (Changes::iterator it = _changes.begin(), end = _changes.end(); it != end; ++it) {
(*it)->commit();
}
// We now reset to a "clean" state without any uncommited changes.
_changes.clear();
invariant(_startOfUncommittedChangesForLevel.front() == 0);
}
void DurRecoveryUnit::rollbackInnermostChanges() {
// TODO SERVER-15043 reduce logging at default verbosity after a burn-in period
invariant(_changes.size() <= size_t(std::numeric_limits<int>::max()));
const int rollbackTo = _startOfUncommittedChangesForLevel.back();
log() << " ***** ROLLING BACK " << (_changes.size() - rollbackTo) << " changes";
for (int i = _changes.size() - 1; i >= rollbackTo; i--) {
const type_info& type = typeid(*_changes[i]);
if (type != typeid(MemoryWrite)) {
log() << "CUSTOM ROLLBACK " << demangleName(type);
}
_changes[i]->rollback();
}
_changes.erase(_changes.begin() + rollbackTo, _changes.end());
if (inOutermostUnitOfWork()) {
// We just rolled back so we are now "clean" and don't need to roll back anymore.
invariant(_changes.empty());
_mustRollback = false;
}
else {
// Inner UOW rolled back, so outer must not commit. We can loosen this in the future,
// but that would require all StorageEngines to support rollback of nested transactions.
_mustRollback = true;
}
}
void DurRecoveryUnit::recordPreimage(char* data, size_t len) {
invariant(len > 0);
registerChange(new MemoryWrite(data, len));
}
bool DurRecoveryUnit::awaitCommit() {
#if ROLLBACK_ENABLED
invariant(!inAUnitOfWork());
#endif
return getDur().awaitCommit();
}
void* DurRecoveryUnit::writingPtr(void* data, size_t len) {
invariant(len > 0);
#if ROLLBACK_ENABLED
invariant(inAUnitOfWork());
// Windows requires us to adjust the address space *before* we write to anything.
MemoryMappedFile::makeWritable(data, len);
registerChange(new MemoryWrite(static_cast<char*>(data), len));
return data;
#else
invariant(_txn->lockState()->isWriteLocked());
return getDur().writingPtr(data, len);
#endif
}
void DurRecoveryUnit::registerChange(Change* change) {
#if ROLLBACK_ENABLED
invariant(inAUnitOfWork());
_changes.push_back(ChangePtr(change));
#else
change->commit();
delete change;
#endif
}
void DurRecoveryUnit::syncDataAndTruncateJournal() {
#if ROLLBACK_ENABLED
publishChanges();
#endif
return getDur().syncDataAndTruncateJournal(_txn);
}
void MemoryWrite::commit() {
// TODO don't go through getDur() interface.
if (getDur().isDurable()) {
getDur().writingPtr(_base, _preimage.size());
}
}
void MemoryWrite::rollback() {
// TODO need to add these pages to our "dirty count" somehow.
_preimage.copy(_base, _preimage.size());
}
} // namespace mongo
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