faster accesstime save restore (#439)

- Improvement: Reduce time a cache bucket is locked for write when flushing/garbage collecting
  - Change format for faster read/write and reduced size on disk
  - Don't lock index while writing manifest to disk
  - Skip garbage collect if we are currently in a Flush operation
  - BlockStore::Flush no longer terminates currently writing block
  - Garbage collect references to currently writing block but keep the block as new data may be added
  - Fix BlockStore::Prune used disk space calculation
  - Don't materialize data in filecas when we just need the size

1 files changed, 12 insertions, 10 deletions

diff --git a/src/zenserver/cache/cachedisklayer.h b/src/zenserver/cache/cachedisklayer.h
index 80c643afa..c4bedfee8 100644
--- a/src/zenserver/cache/cachedisklayer.h
+++ b/src/zenserver/cache/cachedisklayer.h
@@ -188,6 +188,7 @@ private:
 		BlockStore			  m_BlockStore;
 		Oid					  m_BucketId;
 		uint64_t			  m_LargeObjectThreshold = 128 * 1024;
+		std::atomic_bool	  m_IsFlushing{};
 
 		// These files are used to manage storage of small objects for this bucket
 
@@ -221,16 +222,17 @@ private:
 
 		std::atomic_uint64_t m_TotalStandaloneSize{};
 
-		void							BuildPath(PathBuilderBase& Path, const IoHash& HashKey) const;
-		void							PutStandaloneCacheValue(const IoHash& HashKey, const ZenCacheValue& Value);
-		IoBuffer						GetStandaloneCacheValue(const DiskLocation& Loc, const IoHash& HashKey) const;
-		void							PutInlineCacheValue(const IoHash& HashKey, const ZenCacheValue& Value);
-		IoBuffer						GetInlineCacheValue(const DiskLocation& Loc) const;
-		void							MakeIndexSnapshot();
-		uint64_t						ReadIndexFile(const std::filesystem::path& IndexPath, uint32_t& OutVersion);
-		uint64_t						ReadLog(const std::filesystem::path& LogPath, uint64_t LogPosition);
-		void							OpenLog(const bool IsNew);
-		void							SaveManifest();
+		void	 BuildPath(PathBuilderBase& Path, const IoHash& HashKey) const;
+		void	 PutStandaloneCacheValue(const IoHash& HashKey, const ZenCacheValue& Value);
+		IoBuffer GetStandaloneCacheValue(const DiskLocation& Loc, const IoHash& HashKey) const;
+		void	 PutInlineCacheValue(const IoHash& HashKey, const ZenCacheValue& Value);
+		IoBuffer GetInlineCacheValue(const DiskLocation& Loc) const;
+		void	 MakeIndexSnapshot();
+		uint64_t ReadIndexFile(const std::filesystem::path& IndexPath, uint32_t& OutVersion);
+		uint64_t ReadLog(const std::filesystem::path& LogPath, uint64_t LogPosition);
+		void	 OpenLog(const bool IsNew);
+		CbObject MakeManifest(IndexMap&& Index, std::vector<AccessTime>&& AccessTimes, std::vector<BucketPayload>&& Payloads);
+		void	 SaveManifest(CbObject&& Manifest);
 		CacheValueDetails::ValueDetails GetValueDetails(const IoHash& Key, size_t Index) const;
 		// These locks are here to avoid contention on file creation, therefore it's sufficient
 		// that we take the same lock for the same hash