ceph/src/rgw/rgw_bucket_sync_cache.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab ft=cpp
   3
   4 /*
   5  * Ceph - scalable distributed file system
   6  *
   7  * Copyright (C) 2020 Red Hat, Inc
   8  *
   9  * This is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License version 2.1, as published by the Free Software
  12  * Foundation.  See file COPYING.
  13  */
  14
  15 #pragma once
  16
  17 #include <boost/smart_ptr/intrusive_ref_counter.hpp>
  18 #include "common/intrusive_lru.h"
  19 #include "rgw_data_sync.h"
  20
  21 namespace rgw::bucket_sync {
  22
  23 // per bucket-shard state cached by DataSyncShardCR
  24 struct State {
  25   // the source bucket shard to sync
  26   std::pair<rgw_bucket_shard, std::optional<uint64_t>> key;
  27   // current sync obligation being processed by DataSyncSingleEntry
  28   std::optional<rgw_data_sync_obligation> obligation;
  29   // incremented with each new obligation
  30   uint32_t counter = 0;
  31   // highest timestamp applied by all sources
  32   ceph::real_time progress_timestamp;
  33
  34   State(const std::pair<rgw_bucket_shard, std::optional<uint64_t>>& key ) noexcept
  35     : key(key) {}
  36   State(const rgw_bucket_shard& shard, std::optional<uint64_t> gen) noexcept
  37     : key(shard, gen) {}
  38 };
  39
  40 struct Entry;
  41 struct EntryToKey;
  42 class Handle;
  43
  44 using lru_config = ceph::common::intrusive_lru_config<
  45   std::pair<rgw_bucket_shard, std::optional<uint64_t>>, Entry, EntryToKey>;
  46
  47 // a recyclable cache entry
  48 struct Entry : State, ceph::common::intrusive_lru_base<lru_config> {
  49   using State::State;
  50 };
  51
  52 struct EntryToKey {
  53   using type = std::pair<rgw_bucket_shard, std::optional<uint64_t>>;
  54   const type& operator()(const Entry& e) { return e.key; }
  55 };
  56
  57 // use a non-atomic reference count since these aren't shared across threads
  58 template <typename T>
  59 using thread_unsafe_ref_counter = boost::intrusive_ref_counter<
  60     T, boost::thread_unsafe_counter>;
  61
  62 // a state cache for entries within a single datalog shard
  63 class Cache : public thread_unsafe_ref_counter<Cache> {
  64   ceph::common::intrusive_lru<lru_config> cache;
  65  protected:
  66   // protected ctor to enforce the use of factory function create()
  67   explicit Cache(size_t target_size) {
  68     cache.set_target_size(target_size);
  69   }
  70  public:
  71   static boost::intrusive_ptr<Cache> create(size_t target_size) {
  72     return new Cache(target_size);
  73   }
  74
  75   // find or create a cache entry for the given key, and return a Handle that
  76   // keeps it lru-pinned until destruction
  77   Handle get(const rgw_bucket_shard& shard, std::optional<uint64_t> gen);
  78 };
  79
  80 // a State handle that keeps the Cache referenced
  81 class Handle {
  82   boost::intrusive_ptr<Cache> cache;
  83   boost::intrusive_ptr<Entry> entry;
  84  public:
  85   Handle() noexcept = default;
  86   ~Handle() = default;
  87   Handle(boost::intrusive_ptr<Cache> cache,
  88          boost::intrusive_ptr<Entry> entry) noexcept
  89     : cache(std::move(cache)), entry(std::move(entry)) {}
  90   Handle(Handle&&) = default;
  91   Handle(const Handle&) = default;
  92   Handle& operator=(Handle&& o) noexcept {
  93     // move the entry first so that its cache stays referenced over destruction
  94     entry = std::move(o.entry);
  95     cache = std::move(o.cache);
  96     return *this;
  97   }
  98   Handle& operator=(const Handle& o) noexcept {
  99     // copy the entry first so that its cache stays referenced over destruction
 100     entry = o.entry;
 101     cache = o.cache;
 102     return *this;
 103   }
 104
 105   explicit operator bool() const noexcept { return static_cast<bool>(entry); }
 106   State& operator*() const noexcept { return *entry; }
 107   State* operator->() const noexcept { return entry.get(); }
 108 };
 109
 110 inline Handle Cache::get(const rgw_bucket_shard& shard, std::optional<uint64_t> gen)
 111 {
 112   auto result = cache.get_or_create({ shard, gen });
 113   return {this, std::move(result.first)};
 114 }
 115
 116 } // namespace rgw::bucket_sync