ceph/src/rocksdb/include/rocksdb/transaction_log.h

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5
   6 #pragma once
   7
   8 #include <memory>
   9 #include <vector>
  10 #include "rocksdb/status.h"
  11 #include "rocksdb/types.h"
  12 #include "rocksdb/write_batch.h"
  13
  14 namespace ROCKSDB_NAMESPACE {
  15
  16 class LogFile;
  17 typedef std::vector<std::unique_ptr<LogFile>> VectorLogPtr;
  18
  19 enum WalFileType {
  20   /* Indicates that WAL file is in archive directory. WAL files are moved from
  21    * the main db directory to archive directory once they are not live and stay
  22    * there until cleaned up. Files are cleaned depending on archive size
  23    * (Options::WAL_size_limit_MB) and time since last cleaning
  24    * (Options::WAL_ttl_seconds).
  25    */
  26   kArchivedLogFile = 0,
  27
  28   /* Indicates that WAL file is live and resides in the main db directory */
  29   kAliveLogFile = 1
  30 };
  31
  32 class LogFile {
  33  public:
  34   LogFile() {}
  35   virtual ~LogFile() {}
  36
  37   // Returns log file's pathname relative to the main db dir
  38   // Eg. For a live-log-file = /000003.log
  39   //     For an archived-log-file = /archive/000003.log
  40   virtual std::string PathName() const = 0;
  41
  42   // Primary identifier for log file.
  43   // This is directly proportional to creation time of the log file
  44   virtual uint64_t LogNumber() const = 0;
  45
  46   // Log file can be either alive or archived
  47   virtual WalFileType Type() const = 0;
  48
  49   // Starting sequence number of writebatch written in this log file
  50   virtual SequenceNumber StartSequence() const = 0;
  51
  52   // Size of log file on disk in Bytes
  53   virtual uint64_t SizeFileBytes() const = 0;
  54 };
  55
  56 struct BatchResult {
  57   SequenceNumber sequence = 0;
  58   std::unique_ptr<WriteBatch> writeBatchPtr;
  59
  60   // Add empty __ctor and __dtor for the rule of five
  61   // However, preserve the original semantics and prohibit copying
  62   // as the std::unique_ptr member does not copy.
  63   BatchResult() {}
  64
  65   ~BatchResult() {}
  66
  67   BatchResult(const BatchResult&) = delete;
  68
  69   BatchResult& operator=(const BatchResult&) = delete;
  70
  71   BatchResult(BatchResult&& bResult)
  72       : sequence(std::move(bResult.sequence)),
  73         writeBatchPtr(std::move(bResult.writeBatchPtr)) {}
  74
  75   BatchResult& operator=(BatchResult&& bResult) {
  76     sequence = std::move(bResult.sequence);
  77     writeBatchPtr = std::move(bResult.writeBatchPtr);
  78     return *this;
  79   }
  80 };
  81
  82 // A TransactionLogIterator is used to iterate over the transactions in a db.
  83 // One run of the iterator is continuous, i.e. the iterator will stop at the
  84 // beginning of any gap in sequences
  85 class TransactionLogIterator {
  86  public:
  87   TransactionLogIterator() {}
  88   virtual ~TransactionLogIterator() {}
  89
  90   // An iterator is either positioned at a WriteBatch or not valid.
  91   // This method returns true if the iterator is valid.
  92   // Can read data from a valid iterator.
  93   virtual bool Valid() = 0;
  94
  95   // Moves the iterator to the next WriteBatch.
  96   // REQUIRES: Valid() to be true.
  97   virtual void Next() = 0;
  98
  99   // Returns ok if the iterator is valid.
 100   // Returns the Error when something has gone wrong.
 101   virtual Status status() = 0;
 102
 103   // If valid return's the current write_batch and the sequence number of the
 104   // earliest transaction contained in the batch.
 105   // ONLY use if Valid() is true and status() is OK.
 106   virtual BatchResult GetBatch() = 0;
 107
 108   // The read options for TransactionLogIterator.
 109   struct ReadOptions {
 110     // If true, all data read from underlying storage will be
 111     // verified against corresponding checksums.
 112     // Default: true
 113     bool verify_checksums_;
 114
 115     ReadOptions() : verify_checksums_(true) {}
 116
 117     explicit ReadOptions(bool verify_checksums)
 118         : verify_checksums_(verify_checksums) {}
 119   };
 120 };
 121 }  // namespace ROCKSDB_NAMESPACE