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      1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file. See the AUTHORS file for names of contributors.
      4 
      5 #ifndef STORAGE_LEVELDB_DB_DB_IMPL_H_
      6 #define STORAGE_LEVELDB_DB_DB_IMPL_H_
      7 
      8 #include <deque>
      9 #include <set>
     10 #include "db/dbformat.h"
     11 #include "db/log_writer.h"
     12 #include "db/snapshot.h"
     13 #include "leveldb/db.h"
     14 #include "leveldb/env.h"
     15 #include "port/port.h"
     16 #include "port/thread_annotations.h"
     17 
     18 namespace leveldb {
     19 
     20 class MemTable;
     21 class TableCache;
     22 class Version;
     23 class VersionEdit;
     24 class VersionSet;
     25 
     26 class DBImpl : public DB {
     27  public:
     28   DBImpl(const Options& options, const std::string& dbname);
     29   virtual ~DBImpl();
     30 
     31   // Implementations of the DB interface
     32   virtual Status Put(const WriteOptions&, const Slice& key, const Slice& value);
     33   virtual Status Delete(const WriteOptions&, const Slice& key);
     34   virtual Status Write(const WriteOptions& options, WriteBatch* updates);
     35   virtual Status Get(const ReadOptions& options,
     36                      const Slice& key,
     37                      std::string* value);
     38   virtual Iterator* NewIterator(const ReadOptions&);
     39   virtual const Snapshot* GetSnapshot();
     40   virtual void ReleaseSnapshot(const Snapshot* snapshot);
     41   virtual bool GetProperty(const Slice& property, std::string* value);
     42   virtual void GetApproximateSizes(const Range* range, int n, uint64_t* sizes);
     43   virtual void CompactRange(const Slice* begin, const Slice* end);
     44 
     45   // Extra methods (for testing) that are not in the public DB interface
     46 
     47   // Compact any files in the named level that overlap [*begin,*end]
     48   void TEST_CompactRange(int level, const Slice* begin, const Slice* end);
     49 
     50   // Force current memtable contents to be compacted.
     51   Status TEST_CompactMemTable();
     52 
     53   // Return an internal iterator over the current state of the database.
     54   // The keys of this iterator are internal keys (see format.h).
     55   // The returned iterator should be deleted when no longer needed.
     56   Iterator* TEST_NewInternalIterator();
     57 
     58   // Return the maximum overlapping data (in bytes) at next level for any
     59   // file at a level >= 1.
     60   int64_t TEST_MaxNextLevelOverlappingBytes();
     61 
     62   // Record a sample of bytes read at the specified internal key.
     63   // Samples are taken approximately once every config::kReadBytesPeriod
     64   // bytes.
     65   void RecordReadSample(Slice key);
     66 
     67  private:
     68   friend class DB;
     69   struct CompactionState;
     70   struct Writer;
     71 
     72   Iterator* NewInternalIterator(const ReadOptions&,
     73                                 SequenceNumber* latest_snapshot,
     74                                 uint32_t* seed);
     75 
     76   Status NewDB();
     77 
     78   // Recover the descriptor from persistent storage.  May do a significant
     79   // amount of work to recover recently logged updates.  Any changes to
     80   // be made to the descriptor are added to *edit.
     81   Status Recover(VersionEdit* edit) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
     82 
     83   void MaybeIgnoreError(Status* s) const;
     84 
     85   // Delete any unneeded files and stale in-memory entries.
     86   void DeleteObsoleteFiles();
     87 
     88   // Compact the in-memory write buffer to disk.  Switches to a new
     89   // log-file/memtable and writes a new descriptor iff successful.
     90   // Errors are recorded in bg_error_.
     91   void CompactMemTable() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
     92 
     93   Status RecoverLogFile(uint64_t log_number,
     94                         VersionEdit* edit,
     95                         SequenceNumber* max_sequence)
     96       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
     97 
     98   Status WriteLevel0Table(MemTable* mem, VersionEdit* edit, Version* base)
     99       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    100 
    101   Status MakeRoomForWrite(bool force /* compact even if there is room? */)
    102       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    103   WriteBatch* BuildBatchGroup(Writer** last_writer);
    104 
    105   void RecordBackgroundError(const Status& s);
    106 
    107   void MaybeScheduleCompaction() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    108   static void BGWork(void* db);
    109   void BackgroundCall();
    110   void  BackgroundCompaction() EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    111   void CleanupCompaction(CompactionState* compact)
    112       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    113   Status DoCompactionWork(CompactionState* compact)
    114       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    115 
    116   Status OpenCompactionOutputFile(CompactionState* compact);
    117   Status FinishCompactionOutputFile(CompactionState* compact, Iterator* input);
    118   Status InstallCompactionResults(CompactionState* compact)
    119       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
    120 
    121   // Constant after construction
    122   Env* const env_;
    123   const InternalKeyComparator internal_comparator_;
    124   const InternalFilterPolicy internal_filter_policy_;
    125   const Options options_;  // options_.comparator == &internal_comparator_
    126   bool owns_info_log_;
    127   bool owns_cache_;
    128   const std::string dbname_;
    129 
    130   // table_cache_ provides its own synchronization
    131   TableCache* table_cache_;
    132 
    133   // Lock over the persistent DB state.  Non-NULL iff successfully acquired.
    134   FileLock* db_lock_;
    135 
    136   // State below is protected by mutex_
    137   port::Mutex mutex_;
    138   port::AtomicPointer shutting_down_;
    139   port::CondVar bg_cv_;          // Signalled when background work finishes
    140   MemTable* mem_;
    141   MemTable* imm_;                // Memtable being compacted
    142   port::AtomicPointer has_imm_;  // So bg thread can detect non-NULL imm_
    143   WritableFile* logfile_;
    144   uint64_t logfile_number_;
    145   log::Writer* log_;
    146   uint32_t seed_;                // For sampling.
    147 
    148   // Queue of writers.
    149   std::deque<Writer*> writers_;
    150   WriteBatch* tmp_batch_;
    151 
    152   SnapshotList snapshots_;
    153 
    154   // Set of table files to protect from deletion because they are
    155   // part of ongoing compactions.
    156   std::set<uint64_t> pending_outputs_;
    157 
    158   // Has a background compaction been scheduled or is running?
    159   bool bg_compaction_scheduled_;
    160 
    161   // Information for a manual compaction
    162   struct ManualCompaction {
    163     int level;
    164     bool done;
    165     const InternalKey* begin;   // NULL means beginning of key range
    166     const InternalKey* end;     // NULL means end of key range
    167     InternalKey tmp_storage;    // Used to keep track of compaction progress
    168   };
    169   ManualCompaction* manual_compaction_;
    170 
    171   VersionSet* versions_;
    172 
    173   // Have we encountered a background error in paranoid mode?
    174   Status bg_error_;
    175 
    176   // Per level compaction stats.  stats_[level] stores the stats for
    177   // compactions that produced data for the specified "level".
    178   struct CompactionStats {
    179     int64_t micros;
    180     int64_t bytes_read;
    181     int64_t bytes_written;
    182 
    183     CompactionStats() : micros(0), bytes_read(0), bytes_written(0) { }
    184 
    185     void Add(const CompactionStats& c) {
    186       this->micros += c.micros;
    187       this->bytes_read += c.bytes_read;
    188       this->bytes_written += c.bytes_written;
    189     }
    190   };
    191   CompactionStats stats_[config::kNumLevels];
    192 
    193   // No copying allowed
    194   DBImpl(const DBImpl&);
    195   void operator=(const DBImpl&);
    196 
    197   const Comparator* user_comparator() const {
    198     return internal_comparator_.user_comparator();
    199   }
    200 };
    201 
    202 // Sanitize db options.  The caller should delete result.info_log if
    203 // it is not equal to src.info_log.
    204 extern Options SanitizeOptions(const std::string& db,
    205                                const InternalKeyComparator* icmp,
    206                                const InternalFilterPolicy* ipolicy,
    207                                const Options& src);
    208 
    209 }  // namespace leveldb
    210 
    211 #endif  // STORAGE_LEVELDB_DB_DB_IMPL_H_
    212