Make cache MAX_SIZE configurable

implementations/caching/CachingBlockStore.h

@@ -26,7 +26,7 @@ public:
 
 private:
   cpputils::unique_ref<BlockStore> _baseBlockStore;
-  Cache<Key, cpputils::unique_ref<Block>> _cache;
+  Cache<Key, cpputils::unique_ref<Block>, 1000> _cache;
   uint32_t _numNewBlocks;
 
   DISALLOW_COPY_AND_ASSIGN(CachingBlockStore);

implementations/caching/cache/Cache.h

@@ -14,10 +14,9 @@
 namespace blockstore {
 namespace caching {
 
-template<class Key, class Value>
+template<class Key, class Value, uint32_t MAX_ENTRIES>
 class Cache {
 public:
-  static constexpr uint32_t MAX_ENTRIES = 1000;
   //TODO Experiment with good values
   static constexpr double PURGE_LIFETIME_SEC = 0.5; //When an entry has this age, it will be purged from the cache
   static constexpr double PURGE_INTERVAL = 0.5; // With this interval, we check for entries to purge
@@ -44,24 +43,23 @@ private:
   std::unique_ptr<PeriodicTask> _timeoutFlusher;
 };
 
-template<class Key, class Value> constexpr uint32_t Cache<Key, Value>::MAX_ENTRIES;
-template<class Key, class Value> constexpr double Cache<Key, Value>::PURGE_LIFETIME_SEC;
-template<class Key, class Value> constexpr double Cache<Key, Value>::PURGE_INTERVAL;
-template<class Key, class Value> constexpr double Cache<Key, Value>::MAX_LIFETIME_SEC;
+template<class Key, class Value, uint32_t MAX_ENTRIES> constexpr double Cache<Key, Value, MAX_ENTRIES>::PURGE_LIFETIME_SEC;
+template<class Key, class Value, uint32_t MAX_ENTRIES> constexpr double Cache<Key, Value, MAX_ENTRIES>::PURGE_INTERVAL;
+template<class Key, class Value, uint32_t MAX_ENTRIES> constexpr double Cache<Key, Value, MAX_ENTRIES>::MAX_LIFETIME_SEC;
 
-template<class Key, class Value>
-Cache<Key, Value>::Cache(): _cachedBlocks(), _timeoutFlusher(nullptr) {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+Cache<Key, Value, MAX_ENTRIES>::Cache(): _cachedBlocks(), _timeoutFlusher(nullptr) {
   //Don't initialize timeoutFlusher in the initializer list,
   //because it then might already call Cache::popOldEntries() before Cache is done constructing.
   _timeoutFlusher = std::make_unique<PeriodicTask>(std::bind(&Cache::_deleteOldEntriesParallel, this), PURGE_INTERVAL);
 }
 
-template<class Key, class Value>
-Cache<Key, Value>::~Cache() {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+Cache<Key, Value, MAX_ENTRIES>::~Cache() {
 }
 
-template<class Key, class Value>
-boost::optional<Value> Cache<Key, Value>::pop(const Key &key) {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+boost::optional<Value> Cache<Key, Value, MAX_ENTRIES>::pop(const Key &key) {
   std::unique_lock<std::mutex> lock(_mutex);
   cpputils::MutexPoolLock<Key> lockEntryFromBeingPopped(&_currentlyFlushingEntries, key, &lock);
 
@@ -72,16 +70,17 @@ boost::optional<Value> Cache<Key, Value>::pop(const Key &key) {
   return found->releaseValue();
 }
 
-template<class Key, class Value>
-void Cache<Key, Value>::push(const Key &key, Value value) {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::push(const Key &key, Value value) {
   std::unique_lock<std::mutex> lock(_mutex);
+  //std::cout << "Pushing " << key.ToString() << "\n";
   ASSERT(_cachedBlocks.size() <= MAX_ENTRIES, "Cache too full");
   _makeSpaceForEntry(&lock);
   _cachedBlocks.push(key, CacheEntry<Key, Value>(std::move(value)));
 }
 
-template<class Key, class Value>
-void Cache<Key, Value>::_makeSpaceForEntry(std::unique_lock<std::mutex> *lock) {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_makeSpaceForEntry(std::unique_lock<std::mutex> *lock) {
   // _deleteEntry releases the lock while the Value destructor is running.
   // So we can destruct multiple entries in parallel and also call pop() or push() while doing so.
   // However, if another thread calls push() before we get the lock back, the cache is full again.
@@ -92,8 +91,8 @@ void Cache<Key, Value>::_makeSpaceForEntry(std::unique_lock<std::mutex> *lock) {
   ASSERT(_cachedBlocks.size() < MAX_ENTRIES, "Removing entry from cache didn't work");
 };
 
-template<class Key, class Value>
-void Cache<Key, Value>::_deleteEntry(std::unique_lock<std::mutex> *lock) {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_deleteEntry(std::unique_lock<std::mutex> *lock) {
   auto key = _cachedBlocks.peekKey();
   ASSERT(key != boost::none, "There was no entry to delete");
   cpputils::MutexPoolLock<Key> lockEntryFromBeingPopped(&_currentlyFlushingEntries, *key);
@@ -105,8 +104,8 @@ void Cache<Key, Value>::_deleteEntry(std::unique_lock<std::mutex> *lock) {
   lock->lock();
 };
 
-template<class Key, class Value>
-void Cache<Key, Value>::_deleteOldEntriesParallel() {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntriesParallel() {
   unsigned int numThreads = std::max(1u, std::thread::hardware_concurrency());
   std::vector<std::future<void>> waitHandles;
   for (unsigned int i = 0; i < numThreads; ++i) {
@@ -119,13 +118,13 @@ void Cache<Key, Value>::_deleteOldEntriesParallel() {
   }
 };
 
-template<class Key, class Value>
-void Cache<Key, Value>::_deleteOldEntries() {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntries() {
   while (_deleteOldEntry()) {}
 }
 
-template<class Key, class Value>
-bool Cache<Key, Value>::_deleteOldEntry() {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+bool Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntry() {
   // This function can be called in parallel by multiple threads and will then cause the Value destructors
   // to be called in parallel. The call to _deleteEntry() releases the lock while the Value destructor is running.
   std::unique_lock<std::mutex> lock(_mutex);
@@ -137,8 +136,8 @@ bool Cache<Key, Value>::_deleteOldEntry() {
   }
 };
 
-template<class Key, class Value>
-uint32_t Cache<Key, Value>::size() const {
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+uint32_t Cache<Key, Value, MAX_ENTRIES>::size() const {
   std::unique_lock<std::mutex> lock(_mutex);
   return _cachedBlocks.size();
 };

implementations/caching/cache/QueueMap.h

@@ -25,9 +25,7 @@ public:
 
   void push(const Key &key, Value value) {
     auto newEntry = _entries.emplace(std::piecewise_construct, std::forward_as_tuple(key), std::forward_as_tuple(_sentinel.prev, &_sentinel));
-    if(newEntry.second != true) {
-      throw std::logic_error("There is already an element with this key");
-    }
+    ASSERT(newEntry.second == true, "There is already an element with this key");
     newEntry.first->second.init(&newEntry.first->first, std::move(value));
     //The following is ok, because std::unordered_map never invalidates pointers to its entries
     _sentinel.prev->next = &newEntry.first->second;