mariadb-columnstore-engine/storage-manager/src/MetadataFile.h

/* Copyright (C) 2019 MariaDB Corporation

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; version 2 of
   the License.

   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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
   MA 02110-1301, USA. */

#pragma once

#include "Config.h"
#include "SMLogging.h"
#include <string>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdint.h>
#include <vector>
#include <iostream>
#include <unordered_map>
#include <boost/filesystem/path.hpp>

namespace storagemanager
{
struct metadataObject
{
  metadataObject();
  metadataObject(uint64_t offset);  // so we can search mObjects by integer
  metadataObject(uint64_t offset, uint64_t length, const std::string& key);
  uint64_t offset;
  mutable uint64_t length;
  mutable std::string key;
  bool operator<(const metadataObject& b) const
  {
    return offset < b.offset;
  }
};

class MetadataFile
{
 public:
  struct no_create_t
  {
  };
  MetadataFile();
  MetadataFile(const boost::filesystem::path& filename);
  MetadataFile(const boost::filesystem::path& path, no_create_t,
               bool appendExt);  // this one won't create it if it doesn't exist

  // this ctor is 'special'.  It will take an absolute path, and it will assume it points to a metafile
  // meaning, that it doesn't need the metadata prefix prepended, or the .meta extension appended.
  // aside from that, it will behave like the no_create ctor variant above
  // MetadataFile(const boost::filesystem::path &path);
  ~MetadataFile();

  bool exists() const;
  void printObjects() const;
  int stat(struct stat*) const;
  size_t getLength() const;
  // returns the objects needed to update
  std::vector<metadataObject> metadataRead(off_t offset, size_t length) const;
  // updates the metadatafile with new object
  // int writeMetadata(const boost::filesystem::path &filename);
  int writeMetadata();

  // updates the name and length fields of an entry, given the offset
  void updateEntry(off_t offset, const std::string& newName, size_t newLength);
  void updateEntryLength(off_t offset, size_t newLength);
  metadataObject addMetadataObject(const boost::filesystem::path& filename, size_t length);
  bool getEntry(off_t offset, metadataObject* out) const;
  void removeEntry(off_t offset);
  void removeAllEntries();

  // removes p from the json cache.  p should be a fully qualified metadata file
  static void deletedMeta(const boost::filesystem::path& p);

  static std::string getNewKeyFromOldKey(const std::string& oldKey, size_t length = 0);
  static std::string getNewKey(std::string sourceName, size_t offset, size_t length);
  static off_t getOffsetFromKey(const std::string& key);
  static std::string getSourceFromKey(const std::string& key);
  static size_t getLengthFromKey(const std::string& key);
  static void setOffsetInKey(std::string& key, off_t newOffset);
  static void setLengthInKey(std::string& key, size_t newLength);

  // breaks a key into its consitituent fields
  static void breakout(const std::string& key, std::vector<std::string>& out);

  off_t getMetadataNewObjectOffset();
  // this will be a singleton, which stores the config used
  // by all MetadataFile instances so we don't have to keep bothering Config.
  // members are public b/c i don't want to write accessors right now.  Also who cares.
  class MetadataConfig
  {
   public:
    static MetadataConfig* get();
    size_t mObjectSize;
    boost::filesystem::path msMetadataPath;

   private:
    MetadataConfig();
  };

  static void printKPIs();

  typedef boost::shared_ptr<boost::property_tree::ptree> Jsontree_t;

 private:
  MetadataConfig* mpConfig;
  SMLogging* mpLogger;
  int mVersion;
  int mRevision;
  boost::filesystem::path mFilename;
  Jsontree_t jsontree;
  // std::set<metadataObject> mObjects;
  bool _exists;
  void makeEmptyJsonTree();

  class MetadataCache
  {
   public:
    MetadataCache();
    Jsontree_t get(const boost::filesystem::path&);
    void put(const boost::filesystem::path&, const Jsontree_t&);
    void erase(const boost::filesystem::path&);
    boost::mutex& getMutex();

   private:
    // there's a more efficient way to do this, KISS for now.
    typedef std::list<std::string> Lru_t;
    typedef std::unordered_map<std::string, std::pair<Jsontree_t, Lru_t::iterator> > Lookup_t;
    Lookup_t lookup;
    Lru_t lru;
    uint max_lru_size;
    boost::mutex mutex;
  };
  static MetadataCache jsonCache;
};

}  // namespace storagemanager