Add ConcurrentLRUCache (vesoft-inc#1268)

* Add ConcurrentLRUCache

* Address sky's comments

* update mod

* Add evict for specified key

* Remove dependency on time obj

src/common/base/ConcurrentLRUCache.h

@@ -0,0 +1,257 @@
+/* Copyright (c) 2019 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License,
+ * attached with Common Clause Condition 1.0, found in the LICENSES directory.
+ */
+
+#ifndef COMMON_BASE_CONCURRENTLRUCACHE_H_
+#define COMMON_BASE_CONCURRENTLRUCACHE_H_
+
+#include "base/Base.h"
+#include "base/StatusOr.h"
+#include <list>
+#include <utility>
+#include <boost/optional.hpp>
+#include <gtest/gtest_prod.h>
+
+namespace nebula {
+
+template<class Key, class Value>
+class LRU;
+
+template<typename K, typename V>
+class ConcurrentLRUCache final {
+    FRIEND_TEST(ConcurrentLRUCacheTest, SimpleTest);
+
+public:
+    explicit ConcurrentLRUCache(size_t capacity, uint32_t bucketsExp = 4)
+        : bucketsNum_(1 << bucketsExp)
+        , bucketsExp_(bucketsExp) {
+        CHECK(capacity > bucketsNum_ && bucketsNum_ > 0);
+        auto capPerBucket = capacity >> bucketsExp;
+        auto left = capacity;
+        for (uint32_t i = 0; i < bucketsNum_ - 1; i++) {
+            buckets_.emplace_back(capPerBucket);
+            left -= capPerBucket;
+        }
+        CHECK_GT(left, 0);
+        buckets_.emplace_back(left);
+    }
+
+    bool contains(const K& key, int32_t hint = -1) {
+        return buckets_[bucketIndex(key, hint)].contains(key);
+    }
+
+    void insert(const K& key, const V& val, int32_t hint = -1) {
+        buckets_[bucketIndex(key, hint)].insert(key, val);
+    }
+
+    StatusOr<V> get(const K& key, int32_t hint = -1) {
+        return buckets_[bucketIndex(key, hint)].get(key);
+    }
+
+    /**
+     * Insert the {key, val} if key not existed, and return Status::Inserted.
+     * Otherwise, just return the value for the existed key.
+     * */
+    StatusOr<V> putIfAbsent(const K& key, const V& val, int32_t hint = -1) {
+        return buckets_[bucketIndex(key, hint)].putIfAbsent(key, val);
+    }
+
+    void evict(const K& key, int32_t hint = -1) {
+        buckets_[bucketIndex(key, hint)].evict(key);
+    }
+
+    void clear() {
+        for (auto i = 0; i < bucketsNum_; i++) {
+            buckets_[i].clear();
+        }
+    }
+
+private:
+    class Bucket {
+    public:
+        explicit Bucket(size_t capacity)
+            : lru_(std::make_unique<LRU<K, V>>(capacity)) {}
+
+        Bucket(Bucket&& b)
+            : lru_(std::move(b.lru_)) {}
+
+        bool contains(const K& key) {
+            std::lock_guard<std::mutex> guard(lock_);
+            return lru_->contains(key);
+        }
+
+        void insert(const K& key, const V& val) {
+            std::lock_guard<std::mutex> guard(lock_);
+            lru_->insert(key, val);
+        }
+
+        StatusOr<V> get(const K& key) {
+            std::lock_guard<std::mutex> guard(lock_);
+            auto v = lru_->get(key);
+            if (v == boost::none) {
+                return Status::Error();
+            }
+            return std::move(v).value();
+        }
+
+        StatusOr<V> putIfAbsent(const K& key, const V& val) {
+            std::lock_guard<std::mutex> guard(lock_);
+            auto v = lru_->get(key);
+            if (v == boost::none) {
+                lru_->insert(key, val);
+                return Status::Inserted();
+            }
+            return std::move(v).value();
+        }
+
+        void evict(const K& key) {
+            std::lock_guard<std::mutex> guard(lock_);
+            lru_->evict(key);
+        }
+
+        void clear() {
+            std::lock_guard<std::mutex> guard(lock_);
+            lru_->clear();
+        }
+
+    private:
+        std::mutex lock_;
+        std::unique_ptr<LRU<K, V>> lru_;
+    };
+
+
+private:
+    /**
+     * If hint is specified, we could use it to cal the bucket index directly without hash key.
+     * */
+    uint32_t bucketIndex(const K& key, int32_t hint = -1) {
+        return hint >= 0 ? (hint & ((1 << bucketsExp_) - 1))
+                         : (std::hash<K>()(key) & ((1 << bucketsExp_) - 1));
+    }
+
+
+private:
+    std::vector<Bucket> buckets_;
+    uint32_t bucketsNum_ = 1;
+    uint32_t bucketsExp_ = 0;
+};
+
+
+/**
+    It is copied from boost::compute::detail::LRU.
+    The differences:
+    1. Add methed evict(const K& key);
+    2. Instead std::map with std::unordered_map
+    3. Update the code style.
+*/
+template<class Key, class Value>
+class LRU {
+public:
+    typedef Key key_type;
+    typedef Value value_type;
+    typedef std::list<key_type> list_type;
+    typedef std::unordered_map<
+                key_type,
+                std::tuple<value_type, typename list_type::iterator>
+            > map_type;
+
+    explicit LRU(size_t capacity)
+        : capacity_(capacity) {
+    }
+
+    ~LRU() = default;
+
+    size_t size() const {
+        return map_.size();
+    }
+
+    size_t capacity() const {
+        return capacity_;
+    }
+
+    bool empty() const {
+        return map_.empty();
+    }
+
+    bool contains(const key_type& key) {
+        return map_.find(key) != map_.end();
+    }
+
+    void insert(const key_type& key, const value_type& value) {
+        typename map_type::iterator i = map_.find(key);
+        if (i == map_.end()) {
+            // insert item into the cache, but first check if it is full
+            if (size() >= capacity_) {
+                VLOG(3) << "Size:" << size() << ", capacity " << capacity_;
+                // cache is full, evict the least recently used item
+                evict();
+            }
+            // insert the new item
+            list_.push_front(key);
+            map_[key] = std::make_tuple(value, list_.begin());
+            VLOG(3) << "Insert key " << key << ", val " << value;
+        }
+    }
+
+    boost::optional<value_type> get(const key_type& key) {
+        // lookup value in the cache
+        typename map_type::iterator i = map_.find(key);
+        if (i == map_.end()) {
+            // value not in cache
+            VLOG(3) << key  << " not found!";
+            return boost::none;
+        }
+
+        // return the value, but first update its place in the most
+        // recently used list
+        typename list_type::iterator j = std::get<1>(i->second);
+        const value_type& value = std::get<0>(i->second);
+        if (j != list_.begin()) {
+            // move item to the front of the most recently used list
+            list_.erase(j);
+            list_.push_front(key);
+            // update iterator in map
+            j = list_.begin();
+            i->second = std::make_tuple(value, j);
+        }
+        VLOG(3) << "Get key : " << key << ", val: " << value;
+        return value;
+    }
+
+    /**
+     * evict the key if exist.
+     * */
+    void evict(const key_type& key) {
+        auto it = map_.find(key);
+        if (it != map_.end()) {
+            list_.erase(std::get<1>(it->second));
+            map_.erase(it);
+        }
+    }
+
+    void clear() {
+        map_.clear();
+        list_.clear();
+    }
+
+private:
+    void evict() {
+        // evict item from the end of most recently used list
+        typename list_type::iterator i = --list_.end();
+        VLOG(3) << "Evict the oldest key " << *i;
+        map_.erase(*i);
+        list_.erase(i);
+    }
+
+private:
+    map_type map_;
+    list_type list_;
+    size_t capacity_;
+};
+
+}  // namespace nebula
+
+#endif  // COMMON_BASE_CONCURRENTLRUCACHE_H_
+

src/common/base/Status.h

@@ -92,6 +92,8 @@ class Status final {
     bool is##ERROR() const {                            \
         return code() == k##ERROR;                      \
     }
+    // Some succeeded codes
+    STATUS_GENERATOR(Inserted);
 
     // General errors
     STATUS_GENERATOR(Error);
@@ -128,6 +130,7 @@ class Status final {
     enum Code : uint16_t {
         // OK
         kOk                     = 0,
+        kInserted               = 1,
         // 1xx, for general errors
         kError                  = 101,
         kNoSuchFile             = 102,

src/common/base/test/CMakeLists.txt

@@ -89,6 +89,13 @@ nebula_add_test(
     LIBRARIES gtest gtest_main
 )
 
+nebula_add_test(
+    NAME lru_test
+    SOURCES ConcurrentLRUCacheTest.cpp
+    OBJECTS $<TARGET_OBJECTS:base_obj>
+    LIBRARIES gtest gtest_main
+)
+
 nebula_add_executable(
     NAME range_vs_transform_bm
     SOURCES RangeVsTransformBenchmark.cpp