ceph/src/rocksdb/db/logs_with_prep_tracker.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 <stdint.h>
   9 #include <cassert>
  10 #include <cstdlib>
  11 #include <mutex>
  12 #include <unordered_map>
  13 #include <vector>
  14
  15 namespace rocksdb {
  16
  17 // This class is used to track the log files with outstanding prepare entries.
  18 class LogsWithPrepTracker {
  19  public:
  20   // Called when a transaction prepared in `log` has been committed or aborted.
  21   void MarkLogAsHavingPrepSectionFlushed(uint64_t log);
  22   // Called when a transaction is prepared in `log`.
  23   void MarkLogAsContainingPrepSection(uint64_t log);
  24   // Return the earliest log file with outstanding prepare entries.
  25   uint64_t FindMinLogContainingOutstandingPrep();
  26   size_t TEST_PreparedSectionCompletedSize() {
  27     return prepared_section_completed_.size();
  28   }
  29   size_t TEST_LogsWithPrepSize() { return logs_with_prep_.size(); }
  30
  31  private:
  32   // REQUIRES: logs_with_prep_mutex_ held
  33   //
  34   // sorted list of log numbers still containing prepared data.
  35   // this is used by FindObsoleteFiles to determine which
  36   // flushed logs we must keep around because they still
  37   // contain prepared data which has not been committed or rolled back
  38   struct LogCnt {
  39     uint64_t log;  // the log number
  40     uint64_t cnt;  // number of prepared sections in the log
  41   };
  42   std::vector<LogCnt> logs_with_prep_;
  43   std::mutex logs_with_prep_mutex_;
  44
  45   // REQUIRES: prepared_section_completed_mutex_ held
  46   //
  47   // to be used in conjunction with logs_with_prep_.
  48   // once a transaction with data in log L is committed or rolled back
  49   // rather than updating logs_with_prep_ directly we keep track of that
  50   // in prepared_section_completed_ which maps LOG -> instance_count. This helps
  51   // avoiding contention between a commit thread and the prepare threads.
  52   //
  53   // when trying to determine the minimum log still active we first
  54   // consult logs_with_prep_. while that root value maps to
  55   // an equal value in prepared_section_completed_ we erase the log from
  56   // both logs_with_prep_ and prepared_section_completed_.
  57   std::unordered_map<uint64_t, uint64_t> prepared_section_completed_;
  58   std::mutex prepared_section_completed_mutex_;
  59
  60 };
  61 }  // namespace rocksdb