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2q caching #1102

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92 changes: 74 additions & 18 deletions libraries/multi-index-lru/include/userver/multi-index-lru/container.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -64,21 +64,50 @@ using add_seq_index_t = typename add_seq_index<IndexList>::type;
template <typename Value, typename IndexSpecifierList, typename Allocator = std::allocator<Value>>
class Container {
public:
explicit Container(size_t max_size)
: max_size_(max_size)
explicit Container(std::size_t max_size)
: max_size_(max_size), buffer_size_(0)
{}

// for 2Q-caching, "buffer_size" argument represents size of FIFO buffer
// total cache size is sum of max_size and buffer_size
explicit Container(std::size_t max_size, std::size_t buffer_size)
: max_size_(max_size), buffer_size_(buffer_size)
{}

template <typename... Args>
bool emplace(Args&&... args) {
auto& seq_index = container_.template get<0>();
auto result = seq_index.emplace_front(std::forward<Args>(args)...);

if (!result.second) {
seq_index.relocate(seq_index.begin(), result.first);
} else if (seq_index.size() > max_size_) {
seq_index.pop_back();
if (buffer_size_ == 0) {
return emplace_to_container(std::forward<Args>(args)...);
} else {
auto& seq_index = container_.template get<0>();
auto& buffer_seq_index = fifo_buffer_.template get<0>();

auto args_tuple = std::make_tuple(std::forward<Args>(args)...);

auto result = std::apply([&](auto&&... args) {
return seq_index.emplace_front(std::forward<decltype(args)>(args)...);
}, args_tuple);

auto buffer_result = std::apply([&](auto&&... args) {
return buffer_seq_index.emplace_front(std::forward<decltype(args)>(args)...);
}, args_tuple);

if (!buffer_result.second && result.second) {
buffer_seq_index.erase(buffer_result.first);
} else if (!result.second) {
buffer_seq_index.erase(buffer_result.first);
seq_index.relocate(seq_index.begin(), result.first);
if (seq_index.size() > max_size_) {
seq_index.pop_back();
}
} else {
seq_index.erase(result.first);
if (buffer_seq_index.size() > buffer_size_) {
buffer_seq_index.pop_back();
}
}
return buffer_result.second || result.second;
}
return result.second;
}

bool insert(const Value& value) { return emplace(value); }
Expand All @@ -88,30 +117,39 @@ class Container {
template <typename Tag, typename Key>
auto find(const Key& key) {
auto& primary_index = container_.template get<Tag>();
auto& primary_buffer_index = fifo_buffer_.template get<Tag>();
auto it = primary_index.find(key);

if (it != primary_index.end()) {
auto& seq_index = container_.template get<0>();
auto seq_it = container_.template project<0>(it);
seq_index.relocate(seq_index.begin(), seq_it);
return it;
} else {
auto buffer_it = primary_buffer_index.find(key);
if (buffer_it != primary_buffer_index.end()) {
this->insert(*buffer_it);
return primary_index.find(key);
}
}

return it;
return primary_index.end();
}

template <typename Tag, typename Key>
bool contains(const Key& key) {
return this->template find<Tag, Key>(key) != container_.template get<Tag>().end();
return (this->template find<Tag, Key>(key) != container_.template get<Tag>().end());
}

template <typename Tag, typename Key>
bool erase(const Key& key) {
return container_.template get<Tag>().erase(key) > 0;
return (container_.template get<Tag>().erase(key) > 0) ||
(fifo_buffer_.template get<Tag>().erase(key) > 0);
}

std::size_t size() const { return container_.size(); }
bool empty() const { return container_.empty(); }
std::size_t capacity() const { return max_size_; }
std::size_t size() const { return container_.size() + fifo_buffer_.size(); }
bool empty() const { return container_.empty() && fifo_buffer_.empty(); }
std::size_t capacity() const { return max_size_ + buffer_size_; }

void set_capacity(std::size_t new_capacity) {
max_size_ = new_capacity;
Expand All @@ -121,7 +159,7 @@ class Container {
}
}

void clear() { container_.clear(); }
void clear() { container_.clear(); fifo_buffer_.clear(); }

template <typename Tag>
auto end() {
Expand All @@ -132,9 +170,27 @@ class Container {
using ExtendedIndexSpecifierList = impl::add_seq_index_t<IndexSpecifierList>;

using BoostContainer = boost::multi_index::multi_index_container<Value, ExtendedIndexSpecifierList, Allocator>;

// using BoostList = boost::multi_index::multi_index_container<
// Value,
// boost::multi_index::indexed_by<boost::multi_index::sequenced<>>,
// Allocator>;
BoostContainer container_;
BoostContainer fifo_buffer_;
std::size_t max_size_;
std::size_t buffer_size_;

template <typename... Args>
bool emplace_to_container(Args&&... args) {
auto& seq_index = container_.template get<0>();
auto result = seq_index.emplace_front(std::forward<Args>(args)...);

if (!result.second) {
seq_index.relocate(seq_index.begin(), result.first);
} else if (seq_index.size() > max_size_) {
seq_index.pop_back();
}
return result.second;
}
};
} // namespace multi_index_lru

Expand Down
25 changes: 25 additions & 0 deletions libraries/multi-index-lru/src/main_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,31 @@ TEST_F(ProductsTest, ProductEviction) {
EXPECT_EQ(cache.find<NameTag>("Mouse"), cache.end<NameTag>());
}

TEST_F(ProductsTest, 2QCashingBasic) {
ProductCache cache(2, 2);
// container size = 2
// buffer size = 2

cache.emplace(Product{"A1", "Laptop", 999.99});
cache.emplace(Product{"A2", "Mouse", 29.99});

cache.find<SkuTag>("A1");
cache.find<SkuTag>("A2");
// A1 and A2 move to the container

for (int i = 3; i < 100; ++i) {
cache.emplace(Product{"A" + std::to_string(i), "product_" + std::to_string(i), static_cast<double>(i)});
}

EXPECT_TRUE((cache.contains<SkuTag, std::string>("A1")));
EXPECT_TRUE((cache.contains<SkuTag, std::string>("A2"))); // in the container

EXPECT_TRUE((cache.contains<SkuTag, std::string>("A98")));
EXPECT_TRUE((cache.contains<SkuTag, std::string>("A99"))); // in the buffer

EXPECT_FALSE((cache.contains<SkuTag, std::string>("A3"))); // ousted
}

TEST(Snippet, SimpleUsage) {
struct MyValueT {
std::string key;
Expand Down
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