arangodb/arangod/MMFiles/MMFilesEngine.h

////////////////////////////////////////////////////////////////////////////////
/// 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
/// @author Jan Christoph Uhde
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_STORAGE_ENGINE_MMFILES_ENGINE_H
#define ARANGOD_STORAGE_ENGINE_MMFILES_ENGINE_H 1

#include "Basics/Common.h"
#include "Basics/Mutex.h"
#include "MMFiles/MMFilesDatafile.h"
#include "MMFiles/MMFilesCollectorCache.h"
#include "StorageEngine/StorageEngine.h"
#include "VocBase/AccessMode.h"

#include <velocypack/Builder.h>

namespace arangodb {
class MMFilesCleanupThread;
class MMFilesCompactorThread;
class TransactionCollection;
class TransactionState;

namespace transaction {
class ContextData;
}

/// @brief collection file structure
struct MMFilesEngineCollectionFiles {
  std::vector<std::string> journals;
  std::vector<std::string> compactors;
  std::vector<std::string> datafiles;
  std::vector<std::string> indexes;
};

class MMFilesEngine final : public StorageEngine {
 public:

  // create the storage engine
  explicit MMFilesEngine(application_features::ApplicationServer*);

  ~MMFilesEngine();

  // inherited from ApplicationFeature
  // ---------------------------------

  // add the storage engine's specifc options to the global list of options
  void collectOptions(std::shared_ptr<options::ProgramOptions>) override;

  // validate the storage engine's specific options
  void validateOptions(std::shared_ptr<options::ProgramOptions>) override;

  // preparation phase for storage engine. can be used for internal setup.
  // the storage engine must not start any threads here or write any files
  void prepare() override;

  // initialize engine
  void start() override;

  // flush wal wait for collector
  void stop() override;

  transaction::ContextData* createTransactionContextData() override;
  TransactionState* createTransactionState(TRI_vocbase_t*) override;
  TransactionCollection* createTransactionCollection(TransactionState* state, TRI_voc_cid_t cid, AccessMode::Type accessType, int nestingLevel) override;

  // create storage-engine specific collection
  PhysicalCollection* createPhysicalCollection(LogicalCollection*, VPackSlice const&) override;

  // inventory functionality
  // -----------------------

  // fill the Builder object with an array of databases that were detected
  // by the storage engine. this method must sort out databases that were not
  // fully created (see "createDatabase" below). called at server start only
  void getDatabases(arangodb::velocypack::Builder& result) override;

  // fills the provided builder with information about the collection 
  void getCollectionInfo(TRI_vocbase_t* vocbase, TRI_voc_cid_t cid, 
                         arangodb::velocypack::Builder& result, 
                         bool includeIndexes, TRI_voc_tick_t maxTick) override;

  // fill the Builder object with an array of collections (and their corresponding
  // indexes) that were detected by the storage engine. called at server start separately
  // for each database
  int getCollectionsAndIndexes(TRI_vocbase_t* vocbase, arangodb::velocypack::Builder& result,
                               bool wasCleanShutdown, bool isUpgrade) override;
  
  // return the path for a collection
  std::string collectionPath(TRI_vocbase_t const* vocbase, TRI_voc_cid_t id) const override { 
    return collectionDirectory(vocbase->id(), id); 
  }

  // database, collection and index management
  // -----------------------------------------

  // return the path for a database
  std::string databasePath(TRI_vocbase_t const* vocbase) const override {
    return databaseDirectory(vocbase->id());
  }

  virtual TRI_vocbase_t* openDatabase(arangodb::velocypack::Slice const& parameters, bool isUpgrade, int&) override;
  Database* createDatabase(TRI_voc_tick_t id, arangodb::velocypack::Slice const& args, int& status) override {
    status = TRI_ERROR_NO_ERROR;
    return createDatabaseMMFiles(id,args);
  }
  int writeCreateMarker(TRI_voc_tick_t id, VPackSlice const& slice) override;

  void prepareDropDatabase(TRI_vocbase_t* vocbase, bool useWriteMarker, int& status) override;
  void dropDatabase(Database* database, int& status) override;
  void waitUntilDeletion(TRI_voc_tick_t id, bool force, int& status) override;

  // wal in recovery
  bool inRecovery() override;

  // start compactor thread and delete files form collections marked as deleted
  void recoveryDone(TRI_vocbase_t* vocbase) override;

private:
  int dropDatabaseMMFiles(TRI_vocbase_t* vocbase);
  TRI_vocbase_t* createDatabaseMMFiles(TRI_voc_tick_t id, arangodb::velocypack::Slice const& data);

public:
  // asks the storage engine to create a collection as specified in the VPack
  // Slice object and persist the creation info. It is guaranteed by the server 
  // that no other active collection with the same name and id exists in the same
  // database when this function is called. If this operation fails somewhere in 
  // the middle, the storage engine is required to fully clean up the creation 
  // and throw only then, so that subsequent collection creation requests will not fail.
  // the WAL entry for the collection creation will be written *after* the call
  // to "createCollection" returns
  std::string createCollection(TRI_vocbase_t* vocbase, TRI_voc_cid_t id,
                               arangodb::LogicalCollection const* parameters) override;
  
  // asks the storage engine to drop the specified collection and persist the 
  // deletion info. Note that physical deletion of the collection data must not 
  // be carried out by this call, as there may
  // still be readers of the collection's data. It is recommended that this operation
  // only sets a deletion flag for the collection but let's an async task perform
  // the actual deletion.
  // the WAL entry for collection deletion will be written *after* the call
  // to "dropCollection" returns
  void prepareDropCollection(TRI_vocbase_t* vocbase, arangodb::LogicalCollection* collection) override;
  
  // perform a physical deletion of the collection
  void dropCollection(TRI_vocbase_t* vocbase, arangodb::LogicalCollection* collection) override;
  
  // asks the storage engine to change properties of the collection as specified in 
  // the VPack Slice object and persist them. If this operation fails 
  // somewhere in the middle, the storage engine is required to fully revert the 
  // property changes and throw only then, so that subsequent operations will not fail.
  // the WAL entry for the propery change will be written *after* the call
  // to "changeCollection" returns
  void changeCollection(TRI_vocbase_t* vocbase, TRI_voc_cid_t id,
                        arangodb::LogicalCollection const* parameters,
                        bool doSync) override;
  
  // asks the storage engine to create an index as specified in the VPack
  // Slice object and persist the creation info. The database id, collection id 
  // and index data are passed in the Slice object. Note that this function
  // is not responsible for inserting the individual documents into the index.
  // If this operation fails somewhere in the middle, the storage engine is required 
  // to fully clean up the creation and throw only then, so that subsequent index 
  // creation requests will not fail.
  // the WAL entry for the index creation will be written *after* the call
  // to "createIndex" returns
  void createIndex(TRI_vocbase_t* vocbase, TRI_voc_cid_t collectionId,
                   TRI_idx_iid_t id, arangodb::velocypack::Slice const& data) override;
  
  // asks the storage engine to drop the specified index and persist the deletion 
  // info. Note that physical deletion of the index must not be carried out by this call, 
  // as there may still be users of the index. It is recommended that this operation
  // only sets a deletion flag for the index but let's an async task perform
  // the actual deletion.
  // the WAL entry for index deletion will be written *after* the call
  // to "dropIndex" returns
  void dropIndex(TRI_vocbase_t* vocbase, TRI_voc_cid_t collectionId,
                 TRI_idx_iid_t id) override;
  
  void dropIndexWalMarker(TRI_vocbase_t* vocbase, TRI_voc_cid_t collectionId,
                          arangodb::velocypack::Slice const& data, bool writeMarker, int&) override;

  void unloadCollection(TRI_vocbase_t* vocbase, TRI_voc_cid_t collectionId) override;
  
  void signalCleanup(TRI_vocbase_t* vocbase) override;

  // document operations
  // -------------------

  // iterate all documents of the underlying collection
  // this is called when a collection is openend, and all its documents need to be added to
  // indexes etc.
  void iterateDocuments(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId,
                        std::function<void(arangodb::velocypack::Slice const&)> const& cb) override;


  // adds a document to the storage engine
  // this will be called by the WAL collector when surviving documents are being moved
  // into the storage engine's realm
  void addDocumentRevision(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId,
                           arangodb::velocypack::Slice const& document) override;
  
  // removes a document from the storage engine
  // this will be called by the WAL collector when non-surviving documents are being removed
  // from the storage engine's realm
  void removeDocumentRevision(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId,
                              arangodb::velocypack::Slice const& document) override;

  /// @brief scans a collection and locates all files
  MMFilesEngineCollectionFiles scanCollectionDirectory(std::string const& path);

  /// @brief remove data of expired compaction blockers
  bool cleanupCompactionBlockers(TRI_vocbase_t* vocbase) override;

  /// @brief insert a compaction blocker
  int insertCompactionBlocker(TRI_vocbase_t* vocbase, double ttl, TRI_voc_tick_t& id) override;

  /// @brief touch an existing compaction blocker
  int extendCompactionBlocker(TRI_vocbase_t* vocbase, TRI_voc_tick_t id, double ttl) override;

  /// @brief remove an existing compaction blocker
  int removeCompactionBlocker(TRI_vocbase_t* vocbase, TRI_voc_tick_t id) override;

  /// @brief a callback function that is run while it is guaranteed that there is no compaction ongoing
  void preventCompaction(TRI_vocbase_t* vocbase,
                         std::function<void(TRI_vocbase_t*)> const& callback) override;
  
  /// @brief a callback function that is run there is no compaction ongoing
  bool tryPreventCompaction(TRI_vocbase_t* vocbase,
                            std::function<void(TRI_vocbase_t*)> const& callback,
                            bool checkForActiveBlockers) override;
  
  int shutdownDatabase(TRI_vocbase_t* vocbase) override;
  
  int openCollection(TRI_vocbase_t* vocbase, LogicalCollection* collection, bool ignoreErrors) override;
  
  /// @brief transfer markers into a collection
  int transferMarkers(LogicalCollection* collection, MMFilesCollectorCache*,
                      MMFilesOperationsType const&);

  /// @brief Add engine specific AQL functions.

  void addAqlFunctions() const override;
  
 private:
  /// @brief: check the initial markers in a datafile
  bool checkDatafileHeader(MMFilesDatafile* datafile, std::string const& filename) const;

  /// @brief transfer markers into a collection, worker function
  int transferMarkersWorker(LogicalCollection* collection, MMFilesCollectorCache*,
                            MMFilesOperationsType const&);

  /// @brief sync the active journal of a collection
  int syncJournalCollection(LogicalCollection* collection);
  
  /// @brief get the next free position for a new marker of the specified size
  char* nextFreeMarkerPosition(LogicalCollection* collection,
                               TRI_voc_tick_t, TRI_df_marker_type_t,
                               TRI_voc_size_t, MMFilesCollectorCache*);

  /// @brief set the tick of a marker and calculate its CRC value
  void finishMarker(char const*, char*, LogicalCollection* collection,
                    TRI_voc_tick_t, MMFilesCollectorCache*);

  void verifyDirectories(); 
  std::vector<std::string> getDatabaseNames() const;

  /// @brief create a new database directory 
  int createDatabaseDirectory(TRI_voc_tick_t id, std::string const& name);
  
  /// @brief save a parameter.json file for a database
  int saveDatabaseParameters(TRI_voc_tick_t id, std::string const& name, bool deleted);
  
  arangodb::velocypack::Builder databaseToVelocyPack(TRI_voc_tick_t databaseId, 
                                                     std::string const& name, 
                                                     bool deleted) const;

  std::string databaseDirectory(TRI_voc_tick_t databaseId) const;
  std::string databaseParametersFilename(TRI_voc_tick_t databaseId) const;
  std::string collectionDirectory(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId) const;
  std::string collectionParametersFilename(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId) const;
  std::string indexFilename(TRI_voc_tick_t databaseId, TRI_voc_cid_t collectionId, TRI_idx_iid_t indexId) const;
  std::string indexFilename(TRI_idx_iid_t indexId) const;

  int openDatabases();

  /// @brief open an existing database. internal function
  TRI_vocbase_t* openExistingDatabase(TRI_voc_tick_t id, std::string const& name, bool wasCleanShutdown, bool isUpgrade);

  /// @brief note the maximum local tick
  void noteTick(TRI_voc_tick_t tick) {
    if (tick > _maxTick) { _maxTick = tick; }
  }

  /// @brief physically erases the database directory
  int dropDatabaseDirectory(std::string const& path);

  /// @brief iterate over a set of datafiles, identified by filenames
  /// note: the files will be opened and closed
  bool iterateFiles(std::vector<std::string> const& files);

  /// @brief find the maximum tick in a collection's journals
  bool findMaxTickInJournals(std::string const& path);

  /// @brief create a full directory name for a collection
  std::string createCollectionDirectoryName(std::string const& basePath, TRI_voc_cid_t cid);

  void registerCollectionPath(TRI_voc_tick_t databaseId, TRI_voc_cid_t id, std::string const& path);
  void unregisterCollectionPath(TRI_voc_tick_t databaseId, TRI_voc_cid_t id);

  void saveCollectionInfo(TRI_vocbase_t* vocbase,
                          TRI_voc_cid_t id,
                          arangodb::LogicalCollection const* parameters,
                          bool forceSync) const;

  arangodb::velocypack::Builder loadCollectionInfo(TRI_vocbase_t* vocbase, std::string const& path);
  
  // start the cleanup thread for the database 
  int startCleanup(TRI_vocbase_t* vocbase);
  // stop and delete the cleanup thread for the database 
  int stopCleanup(TRI_vocbase_t* vocbase);
 
  // start the compactor thread for the database 
  int startCompactor(TRI_vocbase_t* vocbase);
  // signal the compactor thread to stop
  int beginShutdownCompactor(TRI_vocbase_t* vocbase);
  // stop and delete the compactor thread for the database
  int stopCompactor(TRI_vocbase_t* vocbase);
  
  /// @brief writes a drop-database marker into the log
  int writeDropMarker(TRI_voc_tick_t id);

 public:
  static std::string const EngineName;
  static std::string const FeatureName;

 private:
  std::string _basePath;
  std::string _databasePath;
  bool _isUpgrade;
  TRI_voc_tick_t _maxTick;
  std::vector<std::pair<std::string, std::string>> _deleted;

  arangodb::basics::ReadWriteLock mutable _pathsLock;
  std::unordered_map<TRI_voc_tick_t, std::unordered_map<TRI_voc_cid_t, std::string>> _collectionPaths;

  struct CompactionBlocker {
    CompactionBlocker(TRI_voc_tick_t id, double expires) : _id(id), _expires(expires) {}
    CompactionBlocker() = delete;

    TRI_voc_tick_t _id;
    double _expires;
  };

  // lock for compaction blockers
  arangodb::basics::ReadWriteLock mutable _compactionBlockersLock;
  // cross-database map of compaction blockers, protected by _compactionBlockersLock
  std::unordered_map<TRI_vocbase_t*, std::vector<CompactionBlocker>> _compactionBlockers;
  
  // lock for threads
  arangodb::Mutex _threadsLock;
  // per-database compactor threads, protected by _threadsLock
  std::unordered_map<TRI_vocbase_t*, MMFilesCompactorThread*> _compactorThreads;
  // per-database cleanup threads, protected by _threadsLock
  std::unordered_map<TRI_vocbase_t*, MMFilesCleanupThread*> _cleanupThreads;
};

}

#endif