Limit size of memory cache layer (#423)

- Feature: Limit the size ZenCacheMemoryLayer may use
  - `--cache-memlayer-targetfootprint` option to set which size (in bytes) it should be limited to, zero to have it unbounded
  - `--cache-memlayer-maxage` option to set how long (in seconds) cache items should be kept in the memory cache

Do more "standard" GC rather than clearing everything.
Tries to purge memory on Get/Put on the fly if exceeding limit - not sure if we should have a polling thread instead of adding overhead to Get/Put (however light it may be).

1 files changed, 11 insertions, 4 deletions

diff --git a/src/zenserver/cache/structuredcachestore.h b/src/zenserver/cache/structuredcachestore.h
index 0dd160a98..0c87ecc22 100644
--- a/src/zenserver/cache/structuredcachestore.h
+++ b/src/zenserver/cache/structuredcachestore.h
@@ -39,6 +39,7 @@ namespace zen {
 
 class WorkerThreadPool;
 class DiskWriteBlocker;
+class JobQueue;
 
 /* Z$ namespace
 
@@ -77,7 +78,10 @@ public:
 		ZenCacheDiskLayer::DiskStats  DiskStats;
 	};
 
-	ZenCacheNamespace(GcManager& Gc, const std::filesystem::path& RootDir);
+	ZenCacheNamespace(GcManager&							   Gc,
+					  JobQueue&								   JobQueue,
+					  const std::filesystem::path&			   RootDir,
+					  const ZenCacheMemoryLayer::Configuration MemLayerConfig = {});
 	~ZenCacheNamespace();
 
 	bool Get(std::string_view Bucket, const IoHash& HashKey, ZenCacheValue& OutValue);
@@ -108,6 +112,7 @@ public:
 
 private:
 	std::filesystem::path m_RootDir;
+	JobQueue&			  m_JobQueue;
 	ZenCacheMemoryLayer	  m_MemLayer;
 	ZenCacheDiskLayer	  m_DiskLayer;
 	std::atomic<uint64_t> m_HitCount{};
@@ -137,8 +142,9 @@ public:
 
 	struct Configuration
 	{
-		std::filesystem::path BasePath;
-		bool				  AllowAutomaticCreationOfNamespaces = false;
+		std::filesystem::path			   BasePath;
+		bool							   AllowAutomaticCreationOfNamespaces = false;
+		ZenCacheMemoryLayer::Configuration MemLayerConfig;
 		struct LogConfig
 		{
 			bool EnableWriteLog	 = true;
@@ -171,7 +177,7 @@ public:
 		std::vector<NamedNamespaceStats> NamespaceStats;
 	};
 
-	ZenCacheStore(GcManager& Gc, const Configuration& Configuration, const DiskWriteBlocker* InDiskWriteBlocker);
+	ZenCacheStore(GcManager& Gc, JobQueue& JobQueue, const Configuration& Configuration, const DiskWriteBlocker* InDiskWriteBlocker);
 	~ZenCacheStore();
 
 	bool Get(const CacheRequestContext& Context,
@@ -222,6 +228,7 @@ private:
 	std::vector<std::unique_ptr<ZenCacheNamespace>> m_DroppedNamespaces;
 
 	GcManager&			  m_Gc;
+	JobQueue&			  m_JobQueue;
 	Configuration		  m_Configuration;
 	std::atomic<uint64_t> m_HitCount{};
 	std::atomic<uint64_t> m_MissCount{};