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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <map>
#include <string>
#include "rocksdb/rocksdb_namespace.h"
namespace ROCKSDB_NAMESPACE {
class WriteBatch;
// WALFilter allows an application to inspect write-ahead-log (WAL)
// records or modify their processing on recovery.
// Please see the details below.
class WalFilter {
public:
enum class WalProcessingOption {
// Continue processing as usual
kContinueProcessing = 0,
// Ignore the current record but continue processing of log(s)
kIgnoreCurrentRecord = 1,
// Stop replay of logs and discard logs
// Logs won't be replayed on subsequent recovery
kStopReplay = 2,
// Corrupted record detected by filter
kCorruptedRecord = 3,
// Marker for enum count
kWalProcessingOptionMax = 4
};
virtual ~WalFilter() {}
// Provide ColumnFamily->LogNumber map to filter
// so that filter can determine whether a log number applies to a given
// column family (i.e. that log hasn't been flushed to SST already for the
// column family).
// We also pass in name->id map as only name is known during
// recovery (as handles are opened post-recovery).
// while write batch callbacks happen in terms of column family id.
//
// @params cf_lognumber_map column_family_id to lognumber map
// @params cf_name_id_map column_family_name to column_family_id map
virtual void ColumnFamilyLogNumberMap(
const std::map<uint32_t, uint64_t>& /*cf_lognumber_map*/,
const std::map<std::string, uint32_t>& /*cf_name_id_map*/) {}
// LogRecord is invoked for each log record encountered for all the logs
// during replay on logs on recovery. This method can be used to:
// * inspect the record (using the batch parameter)
// * ignoring current record
// (by returning WalProcessingOption::kIgnoreCurrentRecord)
// * reporting corrupted record
// (by returning WalProcessingOption::kCorruptedRecord)
// * stop log replay
// (by returning kStop replay) - please note that this implies
// discarding the logs from current record onwards.
//
// @params log_number log_number of the current log.
// Filter might use this to determine if the log
// record is applicable to a certain column family.
// @params log_file_name log file name - only for informational purposes
// @params batch batch encountered in the log during recovery
// @params new_batch new_batch to populate if filter wants to change
// the batch (for example to filter some records out,
// or alter some records).
// Please note that the new batch MUST NOT contain
// more records than original, else recovery would
// be failed.
// @params batch_changed Whether batch was changed by the filter.
// It must be set to true if new_batch was populated,
// else new_batch has no effect.
// @returns Processing option for the current record.
// Please see WalProcessingOption enum above for
// details.
virtual WalProcessingOption LogRecordFound(
unsigned long long /*log_number*/, const std::string& /*log_file_name*/,
const WriteBatch& batch, WriteBatch* new_batch, bool* batch_changed) {
// Default implementation falls back to older function for compatibility
return LogRecord(batch, new_batch, batch_changed);
}
// Please see the comments for LogRecord above. This function is for
// compatibility only and contains a subset of parameters.
// New code should use the function above.
virtual WalProcessingOption LogRecord(const WriteBatch& /*batch*/,
WriteBatch* /*new_batch*/,
bool* /*batch_changed*/) const {
return WalProcessingOption::kContinueProcessing;
}
// Returns a name that identifies this WAL filter.
// The name will be printed to LOG file on start up for diagnosis.
virtual const char* Name() const = 0;
};
} // namespace ROCKSDB_NAMESPACE
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