From 2ccdcb5b98b7a14c5daa115fa8c1b14ca4cb9867 Mon Sep 17 00:00:00 2001
From: Sebastian Messmer <mail@smessmer.de>
Date: Wed, 14 Oct 2015 14:40:45 +0200
Subject: [PATCH] Cache destructs elements in parallel in destructor

---
 implementations/caching/CachingBlockStore.cpp |  6 +++
 implementations/caching/CachingBlockStore.h   |  2 +
 implementations/caching/cache/Cache.h         | 42 +++++++++++++++----
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/implementations/caching/CachingBlockStore.cpp b/implementations/caching/CachingBlockStore.cpp
index bf4aef78..055796d4 100644
--- a/implementations/caching/CachingBlockStore.cpp
+++ b/implementations/caching/CachingBlockStore.cpp
@@ -26,7 +26,9 @@ Key CachingBlockStore::createKey() {
 }
 
 optional<unique_ref<Block>> CachingBlockStore::tryCreate(const Key &key, Data data) {
+  ASSERT(_cache.pop(key) == none, "Key already exists in cache");
   //TODO Shouldn't we return boost::none if the key already exists?
+  //TODO Key can also already exist but not be in the cache right now.
   ++_numNewBlocks;
   return unique_ref<Block>(make_unique_ref<CachedBlock>(make_unique_ref<NewBlock>(key, std::move(data), this), this));
 }
@@ -82,5 +84,9 @@ void CachingBlockStore::removeFromBaseStore(cpputils::unique_ref<Block> block) {
   _baseBlockStore->remove(std::move(block));
 }
 
+void CachingBlockStore::flush() {
+  _cache.flush();
+}
+
 }
 }
diff --git a/implementations/caching/CachingBlockStore.h b/implementations/caching/CachingBlockStore.h
index 6d5660f1..c6ee255c 100644
--- a/implementations/caching/CachingBlockStore.h
+++ b/implementations/caching/CachingBlockStore.h
@@ -24,6 +24,8 @@ public:
   boost::optional<cpputils::unique_ref<Block>> tryCreateInBaseStore(const Key &key, cpputils::Data data);
   void removeFromBaseStore(cpputils::unique_ref<Block> block);
 
+  void flush();
+
 private:
   cpputils::unique_ref<BlockStore> _baseBlockStore;
   Cache<Key, cpputils::unique_ref<Block>, 1000> _cache;
diff --git a/implementations/caching/cache/Cache.h b/implementations/caching/cache/Cache.h
index 0ee0938d..89cef733 100644
--- a/implementations/caching/cache/Cache.h
+++ b/implementations/caching/cache/Cache.h
@@ -30,12 +30,16 @@ public:
   void push(const Key &key, Value value);
   boost::optional<Value> pop(const Key &key);
 
+  void flush();
+
 private:
   void _makeSpaceForEntry(std::unique_lock<std::mutex> *lock);
   void _deleteEntry(std::unique_lock<std::mutex> *lock);
   void _deleteOldEntriesParallel();
-  void _deleteOldEntries();
-  bool _deleteOldEntry();
+  void _deleteAllEntriesParallel();
+  void _deleteMatchingEntriesAtBeginningParallel(std::function<bool (const CacheEntry<Key, Value> &)> matches);
+  void _deleteMatchingEntriesAtBeginning(std::function<bool (const CacheEntry<Key, Value> &)> matches);
+  bool _deleteMatchingEntryAtBeginning(std::function<bool (const CacheEntry<Key, Value> &)> matches);
 
   mutable std::mutex _mutex;
   cpputils::LockPool<Key> _currentlyFlushingEntries;
@@ -56,6 +60,8 @@ Cache<Key, Value, MAX_ENTRIES>::Cache(): _cachedBlocks(), _timeoutFlusher(nullpt
 
 template<class Key, class Value, uint32_t MAX_ENTRIES>
 Cache<Key, Value, MAX_ENTRIES>::~Cache() {
+  _deleteAllEntriesParallel();
+  ASSERT(_cachedBlocks.size() == 0, "Error in _deleteAllEntriesParallel()");
 }
 
 template<class Key, class Value, uint32_t MAX_ENTRIES>
@@ -104,13 +110,27 @@ void Cache<Key, Value, MAX_ENTRIES>::_deleteEntry(std::unique_lock<std::mutex> *
   lock->lock();
 };
 
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_deleteAllEntriesParallel() {
+  return _deleteMatchingEntriesAtBeginningParallel([] (const CacheEntry<Key, Value> &) {
+      return true;
+  });
+}
+
 template<class Key, class Value, uint32_t MAX_ENTRIES>
 void Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntriesParallel() {
+  return _deleteMatchingEntriesAtBeginningParallel([] (const CacheEntry<Key, Value> &entry) {
+      return entry.ageSeconds() > PURGE_LIFETIME_SEC;
+  });
+}
+
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::_deleteMatchingEntriesAtBeginningParallel(std::function<bool (const CacheEntry<Key, Value> &)> matches) {
   unsigned int numThreads = std::max(1u, std::thread::hardware_concurrency());
   std::vector<std::future<void>> waitHandles;
   for (unsigned int i = 0; i < numThreads; ++i) {
-    waitHandles.push_back(std::async(std::launch::async, [this] {
-      _deleteOldEntries();
+    waitHandles.push_back(std::async(std::launch::async, [this, matches] {
+      _deleteMatchingEntriesAtBeginning(matches);
     }));
   }
   for (auto & waitHandle : waitHandles) {
@@ -119,16 +139,16 @@ void Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntriesParallel() {
 };
 
 template<class Key, class Value, uint32_t MAX_ENTRIES>
-void Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntries() {
-  while (_deleteOldEntry()) {}
+void Cache<Key, Value, MAX_ENTRIES>::_deleteMatchingEntriesAtBeginning(std::function<bool (const CacheEntry<Key, Value> &)> matches) {
+  while (_deleteMatchingEntryAtBeginning(matches)) {}
 }
 
 template<class Key, class Value, uint32_t MAX_ENTRIES>
-bool Cache<Key, Value, MAX_ENTRIES>::_deleteOldEntry() {
+bool Cache<Key, Value, MAX_ENTRIES>::_deleteMatchingEntryAtBeginning(std::function<bool (const CacheEntry<Key, Value> &)> matches) {
   // 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);
-  if (_cachedBlocks.size() > 0 && _cachedBlocks.peek()->ageSeconds() > PURGE_LIFETIME_SEC) {
+  if (_cachedBlocks.size() > 0 && matches(*_cachedBlocks.peek())) {
     _deleteEntry(&lock);
     return true;
   } else {
@@ -142,6 +162,12 @@ uint32_t Cache<Key, Value, MAX_ENTRIES>::size() const {
   return _cachedBlocks.size();
 };
 
+template<class Key, class Value, uint32_t MAX_ENTRIES>
+void Cache<Key, Value, MAX_ENTRIES>::flush() {
+  //TODO Test flush()
+  return _deleteAllEntriesParallel();
+};
+
 }
 }