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   rgw_bucket_shard 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 rgw_bucket_shard& key) noexcept : key(key) {}
  35 };
  36
  37 struct Entry;
  38 struct EntryToKey;
  39 class Handle;
  40
  41 using lru_config = ceph::common::intrusive_lru_config<
  42     rgw_bucket_shard, Entry, EntryToKey>;
  43
  44 // a recyclable cache entry
  45 struct Entry : State, ceph::common::intrusive_lru_base<lru_config> {
  46   using State::State;
  47 };
  48
  49 struct EntryToKey {
  50   using type = rgw_bucket_shard;
  51   const type& operator()(const Entry& e) { return e.key; }
  52 };
  53
  54 // use a non-atomic reference count since these aren't shared across threads
  55 template <typename T>
  56 using thread_unsafe_ref_counter = boost::intrusive_ref_counter<
  57     T, boost::thread_unsafe_counter>;
  58
  59 // a state cache for entries within a single datalog shard
  60 class Cache : public thread_unsafe_ref_counter<Cache> {
  61   ceph::common::intrusive_lru<lru_config> cache;
  62  protected:
  63   // protected ctor to enforce the use of factory function create()
  64   explicit Cache(size_t target_size) {
  65     cache.set_target_size(target_size);
  66   }
  67  public:
  68   static boost::intrusive_ptr<Cache> create(size_t target_size) {
  69     return new Cache(target_size);
  70   }
  71
  72   // find or create a cache entry for the given key, and return a Handle that
  73   // keeps it lru-pinned until destruction
  74   Handle get(const rgw_bucket_shard& key);
  75 };
  76
  77 // a State handle that keeps the Cache referenced
  78 class Handle {
  79   boost::intrusive_ptr<Cache> cache;
  80   boost::intrusive_ptr<Entry> entry;
  81  public:
  82   Handle() noexcept = default;
  83   ~Handle() = default;
  84   Handle(boost::intrusive_ptr<Cache> cache,
  85          boost::intrusive_ptr<Entry> entry) noexcept
  86     : cache(std::move(cache)), entry(std::move(entry)) {}
  87   Handle(Handle&&) = default;
  88   Handle(const Handle&) = default;
  89   Handle& operator=(Handle&& o) noexcept {
  90     // move the entry first so that its cache stays referenced over destruction
  91     entry = std::move(o.entry);
  92     cache = std::move(o.cache);
  93     return *this;
  94   }
  95   Handle& operator=(const Handle& o) noexcept {
  96     // copy the entry first so that its cache stays referenced over destruction
  97     entry = o.entry;
  98     cache = o.cache;
  99     return *this;
 100   }
 101
 102   explicit operator bool() const noexcept { return static_cast<bool>(entry); }
 103   State& operator*() const noexcept { return *entry; }
 104   State* operator->() const noexcept { return entry.get(); }
 105 };
 106
 107 inline Handle Cache::get(const rgw_bucket_shard& key)
 108 {
 109   auto result = cache.get_or_create(key);
 110   return {this, std::move(result.first)};
 111 }
 112
 113 } // namespace rgw::bucket_sync