arangodb/arangod/MMFiles/MMFilesTransactionCollection.cpp

////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Jan Steemann
////////////////////////////////////////////////////////////////////////////////

#include "MMFilesTransactionCollection.h"
#include "Basics/Exceptions.h"
#include "Logger/Logger.h"
#include "MMFiles/MMFilesCollection.h"
#include "MMFiles/MMFilesDocumentOperation.h"
#include "StorageEngine/TransactionState.h"
#include "Transaction/Hints.h"
#include "Transaction/Methods.h"
#include "VocBase/LogicalCollection.h"

using namespace arangodb;

MMFilesTransactionCollection::MMFilesTransactionCollection(TransactionState* trx,
                                                           TRI_voc_cid_t cid,
                                                           AccessMode::Type accessType,
                                                           int nestingLevel)
    : TransactionCollection(trx, cid, accessType, nestingLevel),
      _operations{_arena},
      _originalRevision(0),
      _compactionLocked(false),
      _waitForSync(false) {}

MMFilesTransactionCollection::~MMFilesTransactionCollection() = default;

/// @brief whether or not any write operations for the collection happened
bool MMFilesTransactionCollection::hasOperations() const {
  return (!_operations.empty());
}

void MMFilesTransactionCollection::addOperation(MMFilesDocumentOperation* operation) {
  _operations.push_back(operation);
}

void MMFilesTransactionCollection::freeOperations(transaction::Methods* activeTrx,
                                                  bool mustRollback) {
  if (!hasOperations()) {
    return;
  }

  bool const isSingleOperationTransaction =
      _transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION);

  // revert all operations
  for (auto it = _operations.rbegin(); it != _operations.rend(); ++it) {
    MMFilesDocumentOperation* op = (*it);

    if (mustRollback) {
      try {
        op->revert(activeTrx);
      } catch (...) {
      }
    }
    delete op;
  }

  auto physical = static_cast<MMFilesCollection*>(_collection->getPhysical());
  TRI_ASSERT(physical != nullptr);

  if (mustRollback) {
    physical->setRevision(_originalRevision, true);
  } else if (!physical->isVolatile() && !isSingleOperationTransaction) {
    // only count logfileEntries if the collection is durable
    physical->increaseUncollectedLogfileEntries(_operations.size());
  }

  _operations.clear();
}

bool MMFilesTransactionCollection::canAccess(AccessMode::Type accessType) const {
  if (_collection == nullptr) {
    if (!_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER) ||
        !_transaction->hasHint(transaction::Hints::Hint::NO_USAGE_LOCK)) {
      // not opened. probably a mistake made by the caller
      return false;
    }
    // ok
  }

  // check if access type matches
  if (AccessMode::isWriteOrExclusive(accessType) &&
      !AccessMode::isWriteOrExclusive(_accessType)) {
    // type doesn't match. probably also a mistake by the caller
    return false;
  }

  return true;
}

int MMFilesTransactionCollection::use(int nestingLevel) {
  if (_nestingLevel != nestingLevel) {
    // only process our own collections
    return TRI_ERROR_NO_ERROR;
  }

  if (_collection == nullptr) {
    // open the collection
    if (!_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER) &&
        !_transaction->hasHint(transaction::Hints::Hint::NO_USAGE_LOCK)) {
      // use and usage-lock
      TRI_vocbase_col_status_e status;

      LOG_TRX("4c87c", TRACE, _transaction, nestingLevel) << "using collection " << _cid;
      TRI_set_errno(TRI_ERROR_NO_ERROR);  // clear error state so can get valid
                                          // error below
      _collection = _transaction->vocbase().useCollection(_cid, status);

      if (!_collection) {
        // must return an error
        return TRI_ERROR_NO_ERROR == TRI_errno() ? TRI_ERROR_INTERNAL : TRI_errno();
      }
    } else {
      // use without usage-lock (lock already set externally)
      _collection = _transaction->vocbase().lookupCollection(_cid);

      if (_collection == nullptr) {
        return TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND;
      }
    }

    // store the waitForSync property
    _waitForSync = _collection->waitForSync();
  }

  TRI_ASSERT(_collection != nullptr);
  auto physical = static_cast<MMFilesCollection*>(_collection->getPhysical());
  TRI_ASSERT(physical != nullptr);

  if (nestingLevel == 0 && AccessMode::isWriteOrExclusive(_accessType)) {
    // read-lock the compaction lock
    if (!_transaction->hasHint(transaction::Hints::Hint::NO_COMPACTION_LOCK)) {
      if (!_compactionLocked) {
        physical->preventCompaction();
        _compactionLocked = true;
      }
    }
  }

  bool shouldLock = _transaction->hasHint(transaction::Hints::Hint::LOCK_ENTIRELY);

  if (!shouldLock) {
    shouldLock = (!AccessMode::isNone(_accessType) &&
                  !_transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION));
  }

  if (shouldLock && !isLocked()) {
    // r/w lock the collection
    int res = doLock(_accessType, nestingLevel);

     // TRI_ERROR_LOCKED is not an error, but it indicates that the lock
     // operation has actually acquired the lock (and that the lock has not
     // been held before)
     if (res != TRI_ERROR_NO_ERROR && res != TRI_ERROR_LOCKED) {
       return res;
     }
  }

  if (AccessMode::isWriteOrExclusive(_accessType) && _originalRevision == 0) {
    // store original revision at transaction start
    _originalRevision = physical->revision();
  }

  return TRI_ERROR_NO_ERROR;
}

void MMFilesTransactionCollection::unuse(int nestingLevel) {
  if (isLocked() && (nestingLevel == 0 || _nestingLevel == nestingLevel)) {
    // unlock our own r/w locks
    doUnlock(_accessType, nestingLevel);
  }

  // the top level transaction releases all collections
  if (nestingLevel == 0 && _collection != nullptr) {
    if (!_transaction->hasHint(transaction::Hints::Hint::NO_COMPACTION_LOCK)) {
      if (AccessMode::isWriteOrExclusive(_accessType) && _compactionLocked) {
        auto physical = static_cast<MMFilesCollection*>(_collection->getPhysical());
        TRI_ASSERT(physical != nullptr);
        // read-unlock the compaction lock
        physical->allowCompaction();
        _compactionLocked = false;
      }
    }

    _lockType = AccessMode::Type::NONE;
  }
}

void MMFilesTransactionCollection::release() {
  // the top level transaction releases all collections
  if (_collection != nullptr) {
    // unuse collection, remove usage-lock
    LOG_TRX("99a8a", TRACE, _transaction, 0) << "unusing collection " << _cid;

    if (!_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER) &&
        !_transaction->hasHint(transaction::Hints::Hint::NO_USAGE_LOCK)) {
      _transaction->vocbase().releaseCollection(_collection.get());
    }
    _collection = nullptr;
  }
}

/// @brief lock a collection
/// returns TRI_ERROR_LOCKED in case the lock was successfully acquired
/// returns TRI_ERROR_NO_ERROR in case the lock does not need to be acquired and
/// no other error occurred returns any other error code otherwise
int MMFilesTransactionCollection::doLock(AccessMode::Type type, int nestingLevel) {
  if (_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER)) {
    // never lock
    return TRI_ERROR_NO_ERROR;
  }

  TRI_ASSERT(_collection != nullptr);

//  if (_transaction->isLockedShard(_collection->name())) {
//    // do not lock by command
//    return TRI_ERROR_NO_ERROR;
//  }

  TRI_ASSERT(!isLocked());
  TRI_ASSERT(_collection);

  auto physical = static_cast<MMFilesCollection*>(_collection->getPhysical());
  TRI_ASSERT(physical != nullptr);

  double timeout = _transaction->timeout();
  if (_transaction->hasHint(transaction::Hints::Hint::TRY_LOCK)) {
    // give up early if we cannot acquire the lock instantly
    timeout = 0.00000001;
  }

  bool const useDeadlockDetector =
      (!_transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION) &&
       !_transaction->hasHint(transaction::Hints::Hint::NO_DLD));

  int res;
  if (!AccessMode::isWriteOrExclusive(type)) {
    LOG_TRX("70bc0", TRACE, _transaction, nestingLevel) << "read-locking collection " << _cid;
    res = physical->lockRead(useDeadlockDetector, _transaction, timeout);
  } else {  // WRITE or EXCLUSIVE
    LOG_TRX("dfffd", TRACE, _transaction, nestingLevel) << "write-locking collection " << _cid;
    res = physical->lockWrite(useDeadlockDetector, _transaction, timeout);
  }

  if (res == TRI_ERROR_NO_ERROR) {
    _lockType = type;
    // not an error, but we use TRI_ERROR_LOCKED to indicate that we actually
    // acquired the lock ourselves
    return TRI_ERROR_LOCKED;
  }

  if (res == TRI_ERROR_LOCK_TIMEOUT && timeout >= 0.1) {
    LOG_TOPIC("81cb4", WARN, Logger::QUERIES)
        << "timed out after " << timeout << " s waiting for "
        << AccessMode::typeString(type) << "-lock on collection '"
        << _collection->name() << "'";
  } else if (res == TRI_ERROR_DEADLOCK) {
    LOG_TOPIC("47ad8", WARN, Logger::QUERIES)
        << "deadlock detected while trying to acquire " << AccessMode::typeString(type)
        << "-lock on collection '" << _collection->name() << "'";
  }

  return res;
}

/// @brief unlock a collection
int MMFilesTransactionCollection::doUnlock(AccessMode::Type type, int nestingLevel) {
  if (_transaction->hasHint(transaction::Hints::Hint::LOCK_NEVER)) {
    // never unlock
    return TRI_ERROR_NO_ERROR;
  }

  TRI_ASSERT(_collection != nullptr);

//  std::string collName(_collection->name());
//  if (_transaction->isLockedShard(collName)) {
//    // do not lock by command
//    return TRI_ERROR_NO_ERROR;
//  }

  TRI_ASSERT(isLocked());

  if (_nestingLevel < nestingLevel) {
    // only process our own collections
    return TRI_ERROR_NO_ERROR;
  }

  if (!AccessMode::isWriteOrExclusive(type) && AccessMode::isWriteOrExclusive(_lockType)) {
    // do not remove a write-lock if a read-unlock was requested!
    return TRI_ERROR_NO_ERROR;
  }
  if (AccessMode::isWriteOrExclusive(type) && !AccessMode::isWriteOrExclusive(_lockType)) {
    // we should never try to write-unlock a collection that we have only
    // read-locked
    LOG_TOPIC("1c9eb", ERR, arangodb::Logger::ENGINES) << "logic error in doUnlock";
    TRI_ASSERT(false);
    return TRI_ERROR_INTERNAL;
  }

  bool const useDeadlockDetector =
      (!_transaction->hasHint(transaction::Hints::Hint::SINGLE_OPERATION) &&
       !_transaction->hasHint(transaction::Hints::Hint::NO_DLD));

  TRI_ASSERT(_collection);
  auto physical = static_cast<MMFilesCollection*>(_collection->getPhysical());
  TRI_ASSERT(physical != nullptr);

  if (!AccessMode::isWriteOrExclusive(_lockType)) {
    LOG_TRX("63161", TRACE, _transaction, nestingLevel) << "read-unlocking collection " << _cid;
    physical->unlockRead(useDeadlockDetector, _transaction);
  } else {  // WRITE or EXCLUSIVE
    LOG_TRX("02543", TRACE, _transaction, nestingLevel) << "write-unlocking collection " << _cid;
    physical->unlockWrite(useDeadlockDetector, _transaction);
  }

  _lockType = AccessMode::Type::NONE;

  return TRI_ERROR_NO_ERROR;
}