ceph/src/rocksdb/include/rocksdb/persistent_cache.h

   1 // Copyright (c) 2013, 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 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   6 // Use of this source code is governed by a BSD-style license that can be
   7 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   8 #pragma once
   9
  10 #include <stdint.h>
  11 #include <memory>
  12 #include <string>
  13
  14 #include "rocksdb/env.h"
  15 #include "rocksdb/slice.h"
  16 #include "rocksdb/statistics.h"
  17 #include "rocksdb/status.h"
  18
  19 namespace rocksdb {
  20
  21 // PersistentCache
  22 //
  23 // Persistent cache interface for caching IO pages on a persistent medium. The
  24 // cache interface is specifically designed for persistent read cache.
  25 class PersistentCache {
  26  public:
  27   typedef std::vector<std::map<std::string, double>> StatsType;
  28
  29   virtual ~PersistentCache() {}
  30
  31   // Insert to page cache
  32   //
  33   // page_key   Identifier to identify a page uniquely across restarts
  34   // data       Page data
  35   // size       Size of the page
  36   virtual Status Insert(const Slice& key, const char* data,
  37                         const size_t size) = 0;
  38
  39   // Lookup page cache by page identifier
  40   //
  41   // page_key   Page identifier
  42   // buf        Buffer where the data should be copied
  43   // size       Size of the page
  44   virtual Status Lookup(const Slice& key, std::unique_ptr<char[]>* data,
  45                         size_t* size) = 0;
  46
  47   // Is cache storing uncompressed data ?
  48   //
  49   // True if the cache is configured to store uncompressed data else false
  50   virtual bool IsCompressed() = 0;
  51
  52   // Return stats as map of {string, double} per-tier
  53   //
  54   // Persistent cache can be initialized as a tier of caches. The stats are per
  55   // tire top-down
  56   virtual StatsType Stats() = 0;
  57
  58   virtual std::string GetPrintableOptions() const = 0;
  59 };
  60
  61 // Factor method to create a new persistent cache
  62 Status NewPersistentCache(Env* const env, const std::string& path,
  63                           const uint64_t size,
  64                           const std::shared_ptr<Logger>& log,
  65                           const bool optimized_for_nvm,
  66                           std::shared_ptr<PersistentCache>* cache);
  67 }  // namespace rocksdb