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rust-rocksdb/db/logs_with_prep_tracker.h

63 lines
2.4 KiB

// 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 <cassert>
#include <cstdint>
#include <cstdlib>
#include <mutex>
#include <unordered_map>
#include <vector>
#include "rocksdb/rocksdb_namespace.h"
namespace ROCKSDB_NAMESPACE {
// This class is used to track the log files with outstanding prepare entries.
class LogsWithPrepTracker {
public:
// Called when a transaction prepared in `log` has been committed or aborted.
void MarkLogAsHavingPrepSectionFlushed(uint64_t log);
// Called when a transaction is prepared in `log`.
void MarkLogAsContainingPrepSection(uint64_t log);
// Return the earliest log file with outstanding prepare entries.
uint64_t FindMinLogContainingOutstandingPrep();
size_t TEST_PreparedSectionCompletedSize() {
return prepared_section_completed_.size();
}
size_t TEST_LogsWithPrepSize() { return logs_with_prep_.size(); }
private:
// REQUIRES: logs_with_prep_mutex_ held
//
// sorted list of log numbers still containing prepared data.
// this is used by FindObsoleteFiles to determine which
// flushed logs we must keep around because they still
// contain prepared data which has not been committed or rolled back
struct LogCnt {
uint64_t log; // the log number
uint64_t cnt; // number of prepared sections in the log
};
std::vector<LogCnt> logs_with_prep_;
std::mutex logs_with_prep_mutex_;
// REQUIRES: prepared_section_completed_mutex_ held
//
// to be used in conjunction with logs_with_prep_.
// once a transaction with data in log L is committed or rolled back
// rather than updating logs_with_prep_ directly we keep track of that
// in prepared_section_completed_ which maps LOG -> instance_count. This helps
// avoiding contention between a commit thread and the prepare threads.
//
// when trying to determine the minimum log still active we first
// consult logs_with_prep_. while that root value maps to
// an equal value in prepared_section_completed_ we erase the log from
// both logs_with_prep_ and prepared_section_completed_.
std::unordered_map<uint64_t, uint64_t> prepared_section_completed_;
std::mutex prepared_section_completed_mutex_;
};
} // namespace ROCKSDB_NAMESPACE