ceph/src/rocksdb/util/delete_scheduler.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under the BSD-style license found in the
   3 //  LICENSE file in the root directory of this source tree. An additional grant
   4 //  of patent rights can be found in the PATENTS file in the same directory.
   5
   6 #pragma once
   7
   8 #ifndef ROCKSDB_LITE
   9
  10 #include <map>
  11 #include <queue>
  12 #include <string>
  13 #include <thread>
  14
  15 #include "monitoring/instrumented_mutex.h"
  16 #include "port/port.h"
  17
  18 #include "rocksdb/status.h"
  19
  20 namespace rocksdb {
  21
  22 class Env;
  23 class Logger;
  24 class SstFileManagerImpl;
  25
  26 // DeleteScheduler allows the DB to enforce a rate limit on file deletion,
  27 // Instead of deleteing files immediately, files are moved to trash_dir
  28 // and deleted in a background thread that apply sleep penlty between deletes
  29 // if they are happening in a rate faster than rate_bytes_per_sec,
  30 //
  31 // Rate limiting can be turned off by setting rate_bytes_per_sec = 0, In this
  32 // case DeleteScheduler will delete files immediately.
  33 class DeleteScheduler {
  34  public:
  35   DeleteScheduler(Env* env, const std::string& trash_dir,
  36                   int64_t rate_bytes_per_sec, Logger* info_log,
  37                   SstFileManagerImpl* sst_file_manager);
  38
  39   ~DeleteScheduler();
  40
  41   // Return delete rate limit in bytes per second
  42   int64_t GetRateBytesPerSecond() { return rate_bytes_per_sec_.load(); }
  43
  44   // Set delete rate limit in bytes per second
  45   void SetRateBytesPerSecond(int64_t bytes_per_sec) {
  46     return rate_bytes_per_sec_.store(bytes_per_sec);
  47   }
  48
  49   // Move file to trash directory and schedule it's deletion
  50   Status DeleteFile(const std::string& fname);
  51
  52   // Wait for all files being deleteing in the background to finish or for
  53   // destructor to be called.
  54   void WaitForEmptyTrash();
  55
  56   // Return a map containing errors that happened in BackgroundEmptyTrash
  57   // file_path => error status
  58   std::map<std::string, Status> GetBackgroundErrors();
  59
  60  private:
  61   Status MoveToTrash(const std::string& file_path, std::string* path_in_trash);
  62
  63   Status DeleteTrashFile(const std::string& path_in_trash,
  64                          uint64_t* deleted_bytes);
  65
  66   void BackgroundEmptyTrash();
  67
  68   Env* env_;
  69   // Path to the trash directory
  70   std::string trash_dir_;
  71   // Maximum number of bytes that should be deleted per second
  72   std::atomic<int64_t> rate_bytes_per_sec_;
  73   // Mutex to protect queue_, pending_files_, bg_errors_, closing_
  74   InstrumentedMutex mu_;
  75   // Queue of files in trash that need to be deleted
  76   std::queue<std::string> queue_;
  77   // Number of files in trash that are waiting to be deleted
  78   int32_t pending_files_;
  79   // Errors that happened in BackgroundEmptyTrash (file_path => error)
  80   std::map<std::string, Status> bg_errors_;
  81   // Set to true in ~DeleteScheduler() to force BackgroundEmptyTrash to stop
  82   bool closing_;
  83   // Condition variable signaled in these conditions
  84   //    - pending_files_ value change from 0 => 1
  85   //    - pending_files_ value change from 1 => 0
  86   //    - closing_ value is set to true
  87   InstrumentedCondVar cv_;
  88   // Background thread running BackgroundEmptyTrash
  89   std::unique_ptr<port::Thread> bg_thread_;
  90   // Mutex to protect threads from file name conflicts
  91   InstrumentedMutex file_move_mu_;
  92   Logger* info_log_;
  93   SstFileManagerImpl* sst_file_manager_;
  94   static const uint64_t kMicrosInSecond = 1000 * 1000LL;
  95 };
  96
  97 }  // namespace rocksdb
  98
  99 #endif  // ROCKSDB_LITE