ceph/src/rocksdb/include/rocksdb/wal_filter.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 <map>
   9 #include <string>
  10
  11 #include "rocksdb/rocksdb_namespace.h"
  12
  13 namespace ROCKSDB_NAMESPACE {
  14
  15 class WriteBatch;
  16
  17 // WALFilter allows an application to inspect write-ahead-log (WAL)
  18 // records or modify their processing on recovery.
  19 // Please see the details below.
  20 class WalFilter {
  21  public:
  22   enum class WalProcessingOption {
  23     // Continue processing as usual
  24     kContinueProcessing = 0,
  25     // Ignore the current record but continue processing of log(s)
  26     kIgnoreCurrentRecord = 1,
  27     // Stop replay of logs and discard logs
  28     // Logs won't be replayed on subsequent recovery
  29     kStopReplay = 2,
  30     // Corrupted record detected by filter
  31     kCorruptedRecord = 3,
  32     // Marker for enum count
  33     kWalProcessingOptionMax = 4
  34   };
  35
  36   virtual ~WalFilter() {}
  37
  38   // Provide ColumnFamily->LogNumber map to filter
  39   // so that filter can determine whether a log number applies to a given
  40   // column family (i.e. that log hasn't been flushed to SST already for the
  41   // column family).
  42   // We also pass in name->id map as only name is known during
  43   // recovery (as handles are opened post-recovery).
  44   // while write batch callbacks happen in terms of column family id.
  45   //
  46   // @params cf_lognumber_map column_family_id to lognumber map
  47   // @params cf_name_id_map   column_family_name to column_family_id map
  48
  49   virtual void ColumnFamilyLogNumberMap(
  50       const std::map<uint32_t, uint64_t>& /*cf_lognumber_map*/,
  51       const std::map<std::string, uint32_t>& /*cf_name_id_map*/) {}
  52
  53   // LogRecord is invoked for each log record encountered for all the logs
  54   // during replay on logs on recovery. This method can be used to:
  55   //  * inspect the record (using the batch parameter)
  56   //  * ignoring current record
  57   //    (by returning WalProcessingOption::kIgnoreCurrentRecord)
  58   //  * reporting corrupted record
  59   //    (by returning WalProcessingOption::kCorruptedRecord)
  60   //  * stop log replay
  61   //    (by returning kStop replay) - please note that this implies
  62   //    discarding the logs from current record onwards.
  63   //
  64   // @params log_number     log_number of the current log.
  65   //                        Filter might use this to determine if the log
  66   //                        record is applicable to a certain column family.
  67   // @params log_file_name  log file name - only for informational purposes
  68   // @params batch          batch encountered in the log during recovery
  69   // @params new_batch      new_batch to populate if filter wants to change
  70   //                        the batch (for example to filter some records out,
  71   //                        or alter some records).
  72   //                        Please note that the new batch MUST NOT contain
  73   //                        more records than original, else recovery would
  74   //                        be failed.
  75   // @params batch_changed  Whether batch was changed by the filter.
  76   //                        It must be set to true if new_batch was populated,
  77   //                        else new_batch has no effect.
  78   // @returns               Processing option for the current record.
  79   //                        Please see WalProcessingOption enum above for
  80   //                        details.
  81   virtual WalProcessingOption LogRecordFound(
  82       unsigned long long /*log_number*/, const std::string& /*log_file_name*/,
  83       const WriteBatch& batch, WriteBatch* new_batch, bool* batch_changed) {
  84     // Default implementation falls back to older function for compatibility
  85     return LogRecord(batch, new_batch, batch_changed);
  86   }
  87
  88   // Please see the comments for LogRecord above. This function is for
  89   // compatibility only and contains a subset of parameters.
  90   // New code should use the function above.
  91   virtual WalProcessingOption LogRecord(const WriteBatch& /*batch*/,
  92                                         WriteBatch* /*new_batch*/,
  93                                         bool* /*batch_changed*/) const {
  94     return WalProcessingOption::kContinueProcessing;
  95   }
  96
  97   // Returns a name that identifies this WAL filter.
  98   // The name will be printed to LOG file on start up for diagnosis.
  99   virtual const char* Name() const = 0;
 100 };
 101
 102 }  // namespace ROCKSDB_NAMESPACE