Make sure we monitor for new project, oplogs, namespaces and buckets during GCv2 (#93)

- Bugfix: Make sure we monitor and include new project/oplogs created during GCv2
- Bugfix: Make sure we monitor and include new namespaces/cache buckets created during GCv2

2 files changed, 414 insertions, 126 deletions

diff --git a/src/zenstore/cache/cachedisklayer.cpp b/src/zenstore/cache/cachedisklayer.cpp
index 9dd2e4a67..f865e1c3c 100644
--- a/src/zenstore/cache/cachedisklayer.cpp
+++ b/src/zenstore/cache/cachedisklayer.cpp
@@ -3383,6 +3383,101 @@ ZenCacheDiskLayer::CacheBucket::RemoveExpiredData(GcCtx& Ctx, GcStats& Stats)
 	return new DiskBucketStoreCompactor(*this, std::move(ExpiredStandaloneKeys));
 }
 
+bool
+ZenCacheDiskLayer::CacheBucket::GetReferencesLocked(GcCtx& Ctx, std::vector<IoHash>& OutReferences)
+{
+	auto GetAttachments = [&](const void* CbObjectData) {
+		CbObjectView Obj(CbObjectData);
+		Obj.IterateAttachments([&](CbFieldView Field) { OutReferences.emplace_back(Field.AsAttachment()); });
+	};
+
+	std::vector<std::pair<IoHash, DiskLocation>> StandaloneKeys;
+	{
+		std::vector<IoHash>					  InlineKeys;
+		std::vector<BlockStoreLocation>		  InlineLocations;
+		std::vector<std::vector<std::size_t>> InlineBlockChunkIndexes;
+
+		{
+			std::unordered_map<uint32_t, std::size_t> BlockIndexToChunkIndexes;
+
+			for (const auto& Entry : m_Index)
+			{
+				if (Ctx.IsCancelledFlag.load())
+				{
+					return false;
+				}
+
+				PayloadIndex		 EntryIndex = Entry.second;
+				const BucketPayload& Payload	= m_Payloads[EntryIndex];
+				const DiskLocation&	 Loc		= Payload.Location;
+
+				if (!Loc.IsFlagSet(DiskLocation::kStructured))
+				{
+					continue;
+				}
+				const IoHash& Key = Entry.first;
+				if (Loc.IsFlagSet(DiskLocation::kStandaloneFile))
+				{
+					StandaloneKeys.push_back(std::make_pair(Key, Loc));
+					continue;
+				}
+
+				BlockStoreLocation ChunkLocation = Loc.GetBlockLocation(m_Configuration.PayloadAlignment);
+				size_t			   ChunkIndex	 = InlineLocations.size();
+				InlineLocations.push_back(ChunkLocation);
+				InlineKeys.push_back(Key);
+				if (auto It = BlockIndexToChunkIndexes.find(ChunkLocation.BlockIndex); It != BlockIndexToChunkIndexes.end())
+				{
+					InlineBlockChunkIndexes[It->second].push_back(ChunkIndex);
+				}
+				else
+				{
+					BlockIndexToChunkIndexes.insert_or_assign(ChunkLocation.BlockIndex, InlineBlockChunkIndexes.size());
+					InlineBlockChunkIndexes.emplace_back(std::vector<size_t>{ChunkIndex});
+				}
+			}
+		}
+
+		for (std::vector<std::size_t> ChunkIndexes : InlineBlockChunkIndexes)
+		{
+			ZEN_ASSERT(!ChunkIndexes.empty());
+
+			bool Continue = m_BlockStore.IterateBlock(
+				InlineLocations,
+				ChunkIndexes,
+				[&](size_t ChunkIndex, const void* Data, uint64_t Size) {
+					ZEN_UNUSED(ChunkIndex, Size);
+					GetAttachments(Data);
+					return !Ctx.IsCancelledFlag.load();
+				},
+				[&](size_t ChunkIndex, BlockStoreFile& File, uint64_t Offset, uint64_t Size) {
+					ZEN_UNUSED(ChunkIndex);
+					GetAttachments(File.GetChunk(Offset, Size).GetData());
+					return !Ctx.IsCancelledFlag.load();
+				});
+
+			if (!Continue && Ctx.IsCancelledFlag.load())
+			{
+				return false;
+			}
+		}
+	}
+	for (const auto& It : StandaloneKeys)
+	{
+		if (Ctx.IsCancelledFlag.load())
+		{
+			return false;
+		}
+
+		IoBuffer Buffer = GetStandaloneCacheValue(It.second, It.first);
+		if (Buffer)
+		{
+			GetAttachments(Buffer.GetData());
+		}
+	}
+	return true;
+}
+
 class DiskBucketReferenceChecker : public GcReferenceChecker
 {
 	using PayloadIndex	= ZenCacheDiskLayer::CacheBucket::PayloadIndex;
@@ -3396,7 +3491,6 @@ public:
 	{
 		try
 		{
-			m_IndexLock.reset();
 			m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
 		}
 		catch (const std::exception& Ex)
@@ -3419,114 +3513,25 @@ public:
 			}
 			ZEN_INFO("GCV2: cachebucket [PRECACHE] '{}': found {} references in {}",
 					 m_CacheBucket.m_BucketDir,
-					 m_PrecachedReferences.size(),
+					 m_References.size(),
 					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
 		});
 
-		auto GetAttachments = [&](const void* CbObjectData) {
-			CbObjectView Obj(CbObjectData);
-			Obj.IterateAttachments([&](CbFieldView Field) { m_PrecachedReferences.emplace_back(Field.AsAttachment()); });
-		};
-
-		// Refresh cache
-		{
-			m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences = std::make_unique<HashSet>(); });
+		m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences = std::make_unique<HashSet>(); });
 
-			std::vector<std::pair<IoHash, DiskLocation>> StandaloneKeys;
-			{
-				std::vector<IoHash>					  InlineKeys;
-				std::vector<BlockStoreLocation>		  InlineLocations;
-				std::vector<std::vector<std::size_t>> InlineBlockChunkIndexes;
-
-				{
-					std::unordered_map<uint32_t, std::size_t> BlockIndexToChunkIndexes;
-
-					RwLock::SharedLockScope IndexLock(m_CacheBucket.m_IndexLock);
-					for (const auto& Entry : m_CacheBucket.m_Index)
-					{
-						if (Ctx.IsCancelledFlag.load())
-						{
-							IndexLock.ReleaseNow();
-							m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
-							return;
-						}
-
-						PayloadIndex		 EntryIndex = Entry.second;
-						const BucketPayload& Payload	= m_CacheBucket.m_Payloads[EntryIndex];
-						const DiskLocation&	 Loc		= Payload.Location;
-
-						if (!Loc.IsFlagSet(DiskLocation::kStructured))
-						{
-							continue;
-						}
-						const IoHash& Key = Entry.first;
-						if (Loc.IsFlagSet(DiskLocation::kStandaloneFile))
-						{
-							StandaloneKeys.push_back(std::make_pair(Key, Loc));
-							continue;
-						}
-
-						BlockStoreLocation ChunkLocation = Loc.GetBlockLocation(m_CacheBucket.m_Configuration.PayloadAlignment);
-						size_t			   ChunkIndex	 = InlineLocations.size();
-						InlineLocations.push_back(ChunkLocation);
-						InlineKeys.push_back(Key);
-						if (auto It = BlockIndexToChunkIndexes.find(ChunkLocation.BlockIndex); It != BlockIndexToChunkIndexes.end())
-						{
-							InlineBlockChunkIndexes[It->second].push_back(ChunkIndex);
-						}
-						else
-						{
-							BlockIndexToChunkIndexes.insert_or_assign(ChunkLocation.BlockIndex, InlineBlockChunkIndexes.size());
-							InlineBlockChunkIndexes.emplace_back(std::vector<size_t>{ChunkIndex});
-						}
-					}
-				}
-
-				for (std::vector<std::size_t> ChunkIndexes : InlineBlockChunkIndexes)
-				{
-					ZEN_ASSERT(!ChunkIndexes.empty());
-
-					bool Continue = m_CacheBucket.m_BlockStore.IterateBlock(
-						InlineLocations,
-						ChunkIndexes,
-						[&](size_t ChunkIndex, const void* Data, uint64_t Size) {
-							ZEN_UNUSED(ChunkIndex, Size);
-							GetAttachments(Data);
-							return !Ctx.IsCancelledFlag.load();
-						},
-						[&](size_t ChunkIndex, BlockStoreFile& File, uint64_t Offset, uint64_t Size) {
-							ZEN_UNUSED(ChunkIndex);
-							GetAttachments(File.GetChunk(Offset, Size).GetData());
-							return !Ctx.IsCancelledFlag.load();
-						});
-
-					if (!Continue && Ctx.IsCancelledFlag.load())
-					{
-						m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
-						return;
-					}
-				}
-			}
-			for (const auto& It : StandaloneKeys)
-			{
-				if (Ctx.IsCancelledFlag.load())
-				{
-					m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
-					return;
-				}
+		RwLock::SharedLockScope IndexLock(m_CacheBucket.m_IndexLock);
+		bool					Continue = m_CacheBucket.GetReferencesLocked(Ctx, m_References);
+		IndexLock.ReleaseNow();
 
-				IoBuffer Buffer = m_CacheBucket.GetStandaloneCacheValue(It.second, It.first);
-				if (Buffer)
-				{
-					GetAttachments(Buffer.GetData());
-				}
-			}
+		if (!Continue)
+		{
+			m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
 		}
 	}
 
-	virtual void LockState(GcCtx& Ctx) override
+	virtual void UpdateLockedState(GcCtx& Ctx) override
 	{
-		ZEN_TRACE_CPU("Z$::Bucket::LockState");
+		ZEN_TRACE_CPU("Z$::Bucket::UpdateLockedState");
 
 		Stopwatch  Timer;
 		const auto _ = MakeGuard([&] {
@@ -3536,32 +3541,28 @@ public:
 			}
 			ZEN_INFO("GCV2: cachebucket [LOCKSTATE] '{}': found {} references in {}",
 					 m_CacheBucket.m_BucketDir,
-					 m_PrecachedReferences.size() + m_UncachedReferences.size(),
+					 m_References.size(),
 					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
 		});
 
-		m_IndexLock = std::make_unique<RwLock::SharedLockScope>(m_CacheBucket.m_IndexLock);
 		if (Ctx.IsCancelledFlag.load())
 		{
-			m_UncachedReferences = {};
-			m_IndexLock.reset();
-			m_CacheBucket.m_IndexLock.WithExclusiveLock([&]() { m_CacheBucket.m_TrackedReferences.reset(); });
+			m_References = {};
+			m_CacheBucket.m_TrackedReferences.reset();
 			return;
 		}
 
 		ZEN_ASSERT(m_CacheBucket.m_TrackedReferences);
 
 		HashSet& AddedReferences(*m_CacheBucket.m_TrackedReferences);
-		m_UncachedReferences.reserve(AddedReferences.size());
-		m_UncachedReferences.insert(m_UncachedReferences.end(), AddedReferences.begin(), AddedReferences.end());
+		m_References.reserve(m_References.size() + AddedReferences.size());
+		m_References.insert(m_References.end(), AddedReferences.begin(), AddedReferences.end());
 		AddedReferences = {};
 	}
 
 	virtual void RemoveUsedReferencesFromSet(GcCtx& Ctx, HashSet& IoCids) override
 	{
 		ZEN_TRACE_CPU("Z$::Bucket::RemoveUsedReferencesFromSet");
-
-		ZEN_ASSERT(m_IndexLock);
 		size_t	   InitialCount = IoCids.size();
 		Stopwatch  Timer;
 		const auto _ = MakeGuard([&] {
@@ -3576,18 +3577,7 @@ public:
 					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
 		});
 
-		for (const IoHash& ReferenceHash : m_PrecachedReferences)
-		{
-			if (IoCids.erase(ReferenceHash) == 1)
-			{
-				if (IoCids.empty())
-				{
-					return;
-				}
-			}
-		}
-
-		for (const IoHash& ReferenceHash : m_UncachedReferences)
+		for (const IoHash& ReferenceHash : m_References)
 		{
 			if (IoCids.erase(ReferenceHash) == 1)
 			{
@@ -3598,10 +3588,8 @@ public:
 			}
 		}
 	}
-	CacheBucket&							 m_CacheBucket;
-	std::unique_ptr<RwLock::SharedLockScope> m_IndexLock;
-	std::vector<IoHash>						 m_PrecachedReferences;
-	std::vector<IoHash>						 m_UncachedReferences;
+	CacheBucket&		m_CacheBucket;
+	std::vector<IoHash> m_References;
 };
 
 std::vector<GcReferenceChecker*>
@@ -3673,6 +3661,12 @@ ZenCacheDiskLayer::CacheBucket::CompactState(RwLock::ExclusiveLockScope&,
 	Reset(m_FreeMemCachedPayloads);
 }
 
+RwLock::SharedLockScope
+ZenCacheDiskLayer::CacheBucket::GetGcReferencerLock()
+{
+	return RwLock::SharedLockScope(m_IndexLock);
+}
+
 #if ZEN_WITH_TESTS
 void
 ZenCacheDiskLayer::CacheBucket::SetAccessTime(const IoHash& HashKey, GcClock::TimePoint Time)
@@ -3763,7 +3757,12 @@ ZenCacheDiskLayer::GetOrCreateBucket(std::string_view InBucket)
 
 	CacheBucket* Result = Bucket.get();
 	m_Buckets.emplace(BucketName, std::move(Bucket));
-
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		if (m_CapturedBuckets)
+		{
+			m_CapturedBuckets->push_back(std::string(BucketName));
+		}
+	});
 	return Result;
 }
 
@@ -4317,6 +4316,60 @@ ZenCacheDiskLayer::GetValueDetails(const std::string_view BucketFilter, const st
 	return Details;
 }
 
+std::vector<RwLock::SharedLockScope>
+ZenCacheDiskLayer::GetGcReferencerLocks()
+{
+	std::vector<RwLock::SharedLockScope> Locks;
+	Locks.emplace_back(RwLock::SharedLockScope(m_Lock));
+	for (auto& Kv : m_Buckets)
+	{
+		Locks.emplace_back(Kv.second->GetGcReferencerLock());
+	}
+	return Locks;
+}
+
+void
+ZenCacheDiskLayer::EnableUpdateCapture()
+{
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		if (m_UpdateCaptureRefCounter == 0)
+		{
+			ZEN_ASSERT(!m_CapturedBuckets);
+			m_CapturedBuckets = std::make_unique<std::vector<std::string>>();
+		}
+		else
+		{
+			ZEN_ASSERT(m_CapturedBuckets);
+		}
+		m_UpdateCaptureRefCounter++;
+	});
+}
+
+void
+ZenCacheDiskLayer::DisableUpdateCapture()
+{
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		ZEN_ASSERT(m_CapturedBuckets);
+		ZEN_ASSERT(m_UpdateCaptureRefCounter > 0);
+		m_UpdateCaptureRefCounter--;
+		if (m_UpdateCaptureRefCounter == 0)
+		{
+			m_CapturedBuckets.reset();
+		}
+	});
+}
+
+std::vector<std::string>
+ZenCacheDiskLayer::GetCapturedBuckets()
+{
+	RwLock::SharedLockScope _(m_UpdateCaptureLock);
+	if (m_CapturedBuckets)
+	{
+		return *m_CapturedBuckets;
+	}
+	return {};
+}
+
 void
 ZenCacheDiskLayer::MemCacheTrim()
 {
diff --git a/src/zenstore/cache/structuredcachestore.cpp b/src/zenstore/cache/structuredcachestore.cpp
index d9c2d3e59..d7d594af7 100644
--- a/src/zenstore/cache/structuredcachestore.cpp
+++ b/src/zenstore/cache/structuredcachestore.cpp
@@ -375,6 +375,23 @@ ZenCacheNamespace::GetValueDetails(const std::string_view BucketFilter, const st
 	return m_DiskLayer.GetValueDetails(BucketFilter, ValueFilter);
 }
 
+std::vector<RwLock::SharedLockScope>
+ZenCacheNamespace::GetGcReferencerLocks()
+{
+	return m_DiskLayer.GetGcReferencerLocks();
+}
+
+void
+ZenCacheNamespace::EnableUpdateCapture()
+{
+	m_DiskLayer.EnableUpdateCapture();
+}
+void
+ZenCacheNamespace::DisableUpdateCapture()
+{
+	m_DiskLayer.DisableUpdateCapture();
+}
+
 #if ZEN_WITH_TESTS
 void
 ZenCacheNamespace::SetAccessTime(std::string_view Bucket, const IoHash& HashKey, GcClock::TimePoint Time)
@@ -439,11 +456,15 @@ ZenCacheStore::ZenCacheStore(GcManager&					  Gc,
 												m_BasePath / fmt::format("{}{}", NamespaceDiskPrefix, NamespaceName),
 												m_Configuration.NamespaceConfig);
 	}
+	m_Gc.AddGcReferencer(*this);
+	m_Gc.AddGcReferenceLocker(*this);
 }
 
 ZenCacheStore::~ZenCacheStore()
 {
 	ZEN_INFO("closing cache store at '{}'", m_BasePath);
+	m_Gc.RemoveGcReferenceLocker(*this);
+	m_Gc.RemoveGcReferencer(*this);
 	SetLoggingConfig({.EnableWriteLog = false, .EnableAccessLog = false});
 	m_Namespaces.clear();
 }
@@ -844,6 +865,14 @@ ZenCacheStore::GetNamespace(std::string_view Namespace)
 																		  m_JobQueue,
 																		  m_BasePath / fmt::format("{}{}", NamespaceDiskPrefix, Namespace),
 																		  m_Configuration.NamespaceConfig));
+
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		if (m_CapturedNamespaces)
+		{
+			m_CapturedNamespaces->push_back(std::string(Namespace));
+		}
+	});
+
 	return NewNamespace.first->second.get();
 }
 
@@ -1003,6 +1032,212 @@ ZenCacheStore::GetBucketInfo(std::string_view NamespaceName, std::string_view Bu
 	return {};
 }
 
+std::vector<RwLock::SharedLockScope>
+ZenCacheStore::LockState(GcCtx&)
+{
+	std::vector<RwLock::SharedLockScope> Locks;
+	Locks.emplace_back(RwLock::SharedLockScope(m_NamespacesLock));
+	for (auto& NamespaceIt : m_Namespaces)
+	{
+		std::vector<RwLock::SharedLockScope> NamespaceLocks = NamespaceIt.second->GetGcReferencerLocks();
+		for (auto It = std::make_move_iterator(NamespaceLocks.begin()); It != std::make_move_iterator(NamespaceLocks.end()); It++)
+		{
+			Locks.emplace_back(std::move(*It));
+		}
+	}
+	return Locks;
+}
+
+void
+ZenCacheStore::EnableUpdateCapture()
+{
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		if (m_UpdateCaptureRefCounter == 0)
+		{
+			ZEN_ASSERT(!m_CapturedNamespaces);
+			m_CapturedNamespaces = std::make_unique<std::vector<std::string>>();
+		}
+		else
+		{
+			ZEN_ASSERT(m_CapturedNamespaces);
+		}
+		m_UpdateCaptureRefCounter++;
+	});
+	for (auto& NamespaceIt : m_Namespaces)
+	{
+		NamespaceIt.second->EnableUpdateCapture();
+	}
+}
+
+void
+ZenCacheStore::DisableUpdateCapture()
+{
+	for (auto& NamespaceIt : m_Namespaces)
+	{
+		NamespaceIt.second->DisableUpdateCapture();
+	}
+	m_UpdateCaptureLock.WithExclusiveLock([&]() {
+		ZEN_ASSERT(m_CapturedNamespaces);
+		ZEN_ASSERT(m_UpdateCaptureRefCounter > 0);
+		m_UpdateCaptureRefCounter--;
+		if (m_UpdateCaptureRefCounter == 0)
+		{
+			m_CapturedNamespaces.reset();
+		}
+	});
+}
+
+std::vector<std::string>
+ZenCacheStore::GetCapturedNamespaces()
+{
+	RwLock::SharedLockScope _(m_UpdateCaptureLock);
+	if (m_CapturedNamespaces)
+	{
+		return *m_CapturedNamespaces;
+	}
+	return {};
+}
+
+std::string
+ZenCacheStore::GetGcName(GcCtx&)
+{
+	return fmt::format("zencachestore: '{}'", m_BasePath.string());
+}
+
+GcStoreCompactor*
+ZenCacheStore::RemoveExpiredData(GcCtx&, GcStats&)
+{
+	return nullptr;
+}
+
+class CacheStoreReferenceChecker : public GcReferenceChecker
+{
+public:
+	CacheStoreReferenceChecker(ZenCacheStore& InCacheStore) : m_CacheStore(InCacheStore) { m_CacheStore.EnableUpdateCapture(); }
+
+	virtual ~CacheStoreReferenceChecker()
+	{
+		try
+		{
+			m_CacheStore.DisableUpdateCapture();
+		}
+		catch (const std::exception& Ex)
+		{
+			ZEN_ERROR("~CacheStoreReferenceChecker threw exception: '{}'", Ex.what());
+		}
+	}
+
+	virtual std::string GetGcName(GcCtx&) override { return "cachestore"; }
+	virtual void		PreCache(GcCtx&) override {}
+	virtual void		UpdateLockedState(GcCtx& Ctx) override
+	{
+		ZEN_TRACE_CPU("Z$::UpdateLockedState");
+
+		Stopwatch Timer;
+
+		std::vector<ZenCacheDiskLayer::CacheBucket*> AddedBuckets;
+
+		const auto _ = MakeGuard([&] {
+			if (!Ctx.Settings.Verbose)
+			{
+				return;
+			}
+			ZEN_INFO("GCV2: cachestore [LOCKSTATE] '{}': found {} references in {} in {} new buckets",
+					 "cachestore",
+					 m_References.size(),
+					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()),
+					 AddedBuckets.size());
+		});
+
+		std::vector<std::string> AddedNamespaces = m_CacheStore.GetCapturedNamespaces();
+
+		for (const std::string& AddedNamespace : AddedNamespaces)
+		{
+			if (auto It = m_CacheStore.m_Namespaces.find(AddedNamespace); It != m_CacheStore.m_Namespaces.end())
+			{
+				ZenCacheNamespace& Namespace = *It->second;
+				for (auto& BucketKV : Namespace.m_DiskLayer.m_Buckets)
+				{
+					AddedBuckets.push_back(BucketKV.second.get());
+				}
+			}
+		}
+		for (auto& NamepaceKV : m_CacheStore.m_Namespaces)
+		{
+			ZenCacheNamespace&		 Namespace			   = *NamepaceKV.second;
+			std::vector<std::string> NamespaceAddedBuckets = Namespace.m_DiskLayer.GetCapturedBuckets();
+			for (const std::string& AddedBucketName : NamespaceAddedBuckets)
+			{
+				if (auto It = Namespace.m_DiskLayer.m_Buckets.find(AddedBucketName); It != Namespace.m_DiskLayer.m_Buckets.end())
+				{
+					AddedBuckets.push_back(It->second.get());
+				}
+			}
+		}
+
+		for (ZenCacheDiskLayer::CacheBucket* Bucket : AddedBuckets)
+		{
+			bool Continue = Bucket->GetReferencesLocked(Ctx, m_References);
+			if (!Continue)
+			{
+				break;
+			}
+		}
+	}
+
+	virtual void RemoveUsedReferencesFromSet(GcCtx& Ctx, HashSet& IoCids) override
+	{
+		ZEN_TRACE_CPU("Z$::RemoveUsedReferencesFromSet");
+
+		size_t	   InitialCount = IoCids.size();
+		Stopwatch  Timer;
+		const auto _ = MakeGuard([&] {
+			if (!Ctx.Settings.Verbose)
+			{
+				return;
+			}
+			ZEN_INFO("GCV2: projectstore [FILTER REFERENCES] '{}': filtered out {} used references out of {} in {}",
+					 "projectstore",
+					 InitialCount - IoCids.size(),
+					 InitialCount,
+					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+		});
+
+		for (const IoHash& ReferenceHash : m_References)
+		{
+			if (IoCids.erase(ReferenceHash) == 1)
+			{
+				if (IoCids.empty())
+				{
+					return;
+				}
+			}
+		}
+	}
+
+private:
+	ZenCacheStore&		m_CacheStore;
+	std::vector<IoHash> m_References;
+};
+
+std::vector<GcReferenceChecker*>
+ZenCacheStore::CreateReferenceCheckers(GcCtx& Ctx)
+{
+	ZEN_TRACE_CPU("CacheStore::CreateReferenceCheckers");
+
+	Stopwatch						 Timer;
+	const auto						 _ = MakeGuard([&] {
+		  if (!Ctx.Settings.Verbose)
+		  {
+			  return;
+		  }
+		  ZEN_INFO("GCV2: cachestore [CREATE CHECKERS] '{}': completed in {}", m_BasePath, NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+	  });
+	std::vector<GcReferenceChecker*> Checkers;
+	Checkers.emplace_back(new CacheStoreReferenceChecker(*this));
+	return Checkers;
+}
+
 //////////////////////////////////////////////////////////////////////////
 
 #if ZEN_WITH_TESTS