zen build cache service (#318)

- **EXPERIMENTAL** `zen builds`
  - Feature: `--zen-cache-host` option for `upload` and `download` operations to use a zenserver host `/builds` endpoint for storing build blob and blob metadata
  - Feature: New `/builds` endpoint for caching build blobs and blob metadata
    - `/builds/{namespace}/{bucket}/{buildid}/blobs/{hash}` `GET` and `PUT` method for storing and fetching blobs
    - `/builds/{namespace}/{bucket}/{buildid}/blobs/putBlobMetadata` `POST` method for storing metadata about blobs
    - `/builds/{namespace}/{bucket}/{buildid}/blobs/getBlobMetadata` `POST` method for fetching metadata about blobs
    - `/builds/{namespace}/{bucket}/{buildid}/blobs/exists` `POST` method for checking existance of blobs

3 files changed, 55 insertions, 4 deletions

diff --git a/src/zenutil/include/zenutil/buildstorage.h b/src/zenutil/include/zenutil/buildstorage.h
index 2ebd65a00..f8c7c012c 100644
--- a/src/zenutil/include/zenutil/buildstorage.h
+++ b/src/zenutil/include/zenutil/buildstorage.h
@@ -54,9 +54,9 @@ public:
 		uint64_t																			   ChunkSize,
 		std::function<void(uint64_t Offset, const IoBuffer& Chunk, uint64_t BytesRemaining)>&& Receiver) = 0;
 
-	virtual void PutBlockMetadata(const Oid& BuildId, const IoHash& BlockRawHash, const CbObject& MetaData)				 = 0;
-	virtual std::vector<ChunkBlockDescription> FindBlocks(const Oid& BuildId)											 = 0;
-	virtual std::vector<ChunkBlockDescription> GetBlockMetadata(const Oid& BuildId, std::span<const IoHash> BlockHashes) = 0;
+	virtual void	 PutBlockMetadata(const Oid& BuildId, const IoHash& BlockRawHash, const CbObject& MetaData) = 0;
+	virtual CbObject FindBlocks(const Oid& BuildId)																= 0;
+	virtual CbObject GetBlockMetadatas(const Oid& BuildId, std::span<const IoHash> BlockHashes)					= 0;
 
 	virtual void PutBuildPartStats(const Oid& BuildId, const Oid& BuildPartId, const tsl::robin_map<std::string, double>& FloatStats) = 0;
 };
diff --git a/src/zenutil/include/zenutil/buildstoragecache.h b/src/zenutil/include/zenutil/buildstoragecache.h
new file mode 100644
index 000000000..08c936bf5
--- /dev/null
+++ b/src/zenutil/include/zenutil/buildstoragecache.h
@@ -0,0 +1,52 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zencore/logging.h>
+
+#include <zencore/compactbinary.h>
+#include <zencore/compositebuffer.h>
+#include <zenutil/chunkblock.h>
+
+namespace zen {
+
+class HttpClient;
+
+class BuildStorageCache
+{
+public:
+	struct Statistics
+	{
+		std::atomic<uint64_t> TotalBytesRead	   = 0;
+		std::atomic<uint64_t> TotalBytesWritten	   = 0;
+		std::atomic<uint64_t> TotalRequestCount	   = 0;
+		std::atomic<uint64_t> TotalRequestTimeUs   = 0;
+		std::atomic<uint64_t> TotalExecutionTimeUs = 0;
+	};
+
+	virtual ~BuildStorageCache() {}
+
+	virtual void PutBuildBlob(const Oid& BuildId, const IoHash& RawHash, ZenContentType ContentType, const CompositeBuffer& Payload) = 0;
+	virtual IoBuffer GetBuildBlob(const Oid&	BuildId,
+								  const IoHash& RawHash,
+								  uint64_t		RangeOffset = 0,
+								  uint64_t		RangeBytes	= (uint64_t)-1)																 = 0;
+
+	virtual void PutBlobMetadatas(const Oid& BuildId, std::span<const IoHash> BlobHashes, std::span<const CbObject> MetaDatas) = 0;
+	virtual std::vector<CbObject> GetBlobMetadatas(const Oid& BuildId, std::span<const IoHash> BlobHashes)					   = 0;
+
+	struct BlobExistsResult
+	{
+		bool HasBody	 = 0;
+		bool HasMetadata = 0;
+	};
+
+	virtual std::vector<BlobExistsResult> BlobsExists(const Oid& BuildId, std::span<const IoHash> BlobHashes) = 0;
+};
+
+std::unique_ptr<BuildStorageCache> CreateZenBuildStorageCache(HttpClient&					 HttpClient,
+															  BuildStorageCache::Statistics& Stats,
+															  std::string_view				 Namespace,
+															  std::string_view				 Bucket,
+															  const std::filesystem::path&	 TempFolderPath);
+}  // namespace zen
diff --git a/src/zenutil/include/zenutil/logging/rotatingfilesink.h b/src/zenutil/include/zenutil/logging/rotatingfilesink.h
index 758722156..cd28bdcb2 100644
--- a/src/zenutil/include/zenutil/logging/rotatingfilesink.h
+++ b/src/zenutil/include/zenutil/logging/rotatingfilesink.h
@@ -27,7 +27,6 @@ public:
 	{
 		ZEN_MEMSCOPE(ELLMTag::Logging);
 
-		ZEN_MEMSCOPE(ELLMTag::Logging);
 		std::error_code Ec;
 		if (RotateOnOpen)
 		{