rgw: add data sync cache for bucket shards

Signed-off-by: Casey Bodley <cbodley@redhat.com>

diff --git a/src/rgw/rgw_bucket_sync_cache.h b/src/rgw/rgw_bucket_sync_cache.h
new file mode 100644 (file)
index 0000000..b781e92
--- /dev/null
+++ b/src/rgw/rgw_bucket_sync_cache.h
@@ -0,0 +1,111 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab ft=cpp
+
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2020 Red Hat, Inc
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ */
+
+#pragma once
+
+#include <boost/smart_ptr/intrusive_ref_counter.hpp>
+#include "common/intrusive_lru.h"
+#include "rgw_data_sync.h"
+
+namespace rgw::bucket_sync {
+
+// per bucket-shard state cached by DataSyncShardCR
+struct State {
+  // the source bucket shard to sync
+  rgw_bucket_shard key;
+  // current sync obligation being processed by DataSyncSingleEntry
+  std::optional<rgw_data_sync_obligation> obligation;
+  // highest timestamp applied by all sources
+  ceph::real_time progress_timestamp;
+
+  State(const rgw_bucket_shard& key) noexcept : key(key) {}
+};
+
+struct Entry;
+struct EntryToKey;
+class Handle;
+
+using lru_config = ceph::common::intrusive_lru_config<
+    rgw_bucket_shard, Entry, EntryToKey>;
+
+// a recyclable cache entry
+struct Entry : State, ceph::common::intrusive_lru_base<lru_config> {
+  using State::State;
+};
+
+struct EntryToKey {
+  using type = rgw_bucket_shard;
+  const type& operator()(const Entry& e) { return e.key; }
+};
+
+// use a non-atomic reference count since these aren't shared across threads
+template <typename T>
+using thread_unsafe_ref_counter = boost::intrusive_ref_counter<
+    T, boost::thread_unsafe_counter>;
+
+// a state cache for entries within a single datalog shard
+class Cache : public thread_unsafe_ref_counter<Cache> {
+  ceph::common::intrusive_lru<lru_config> cache;
+ protected:
+  // protected ctor to enforce the use of factory function create()
+  explicit Cache(size_t target_size) {
+    cache.set_target_size(target_size);
+  }
+ public:
+  static boost::intrusive_ptr<Cache> create(size_t target_size) {
+    return new Cache(target_size);
+  }
+
+  // find or create a cache entry for the given key, and return a Handle that
+  // keeps it lru-pinned until destruction
+  Handle get(const rgw_bucket_shard& key);
+};
+
+// a State handle that keeps the Cache referenced
+class Handle {
+  boost::intrusive_ptr<Cache> cache;
+  boost::intrusive_ptr<Entry> entry;
+ public:
+  Handle() noexcept = default;
+  ~Handle() = default;
+  Handle(boost::intrusive_ptr<Cache> cache,
+         boost::intrusive_ptr<Entry> entry) noexcept
+    : cache(std::move(cache)), entry(std::move(entry)) {}
+  Handle(Handle&&) noexcept = default;
+  Handle(const Handle&) noexcept = default;
+  Handle& operator=(Handle&& o) noexcept {
+    // move the entry first so that its cache stays referenced over destruction
+    entry = std::move(o.entry);
+    cache = std::move(o.cache);
+    return *this;
+  }
+  Handle& operator=(const Handle& o) noexcept {
+    // copy the entry first so that its cache stays referenced over destruction
+    entry = o.entry;
+    cache = o.cache;
+    return *this;
+  }
+
+  explicit operator bool() const noexcept { return static_cast<bool>(entry); }
+  State& operator*() const noexcept { return *entry; }
+  State* operator->() const noexcept { return entry.get(); }
+};
+
+inline Handle Cache::get(const rgw_bucket_shard& key)
+{
+  auto result = cache.get_or_create(key);
+  return {this, std::move(result.first)};
+}
+
+} // namespace rgw::bucket_sync