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, 40 insertions, 32 deletions

diff --git a/src/zenserver/config.h b/src/zenserver/config.h
index bb6e20bb6..924375a19 100644
--- a/src/zenserver/config.h
+++ b/src/zenserver/config.h
@@ -116,40 +116,48 @@ struct ZenObjectStoreConfig
 	std::vector<BucketConfig> Buckets;
 };
 
+struct ZenStructuredCacheConfig
+{
+	bool	 Enabled				 = true;
+	bool	 WriteLogEnabled		 = false;
+	bool	 AccessLogEnabled		 = false;
+	uint64_t MemTargetFootprintBytes = 512 * 1024 * 1024;
+	uint64_t MemTrimIntervalSeconds	 = 60;
+	uint64_t MemMaxAgeSeconds		 = gsl::narrow<uint64_t>(std::chrono::seconds(std::chrono::days(1)).count());
+};
+
 struct ZenServerOptions
 {
-	ZenUpstreamCacheConfig UpstreamCacheConfig;
-	ZenGcConfig			   GcConfig;
-	ZenAuthConfig		   AuthConfig;
-	ZenObjectStoreConfig   ObjectStoreConfig;
-	zen::HttpServerConfig  HttpServerConfig;
-	std::filesystem::path  DataDir;						   // Root directory for state (used for testing)
-	std::filesystem::path  ContentDir;					   // Root directory for serving frontend content (experimental)
-	std::filesystem::path  AbsLogFile;					   // Absolute path to main log file
-	std::filesystem::path  ConfigFile;					   // Path to Lua config file
-	std::string			   ChildId;						   // Id assigned by parent process (used for lifetime management)
-	std::string			   LogId;						   // Id for tagging log output
-	std::string			   EncryptionKey;				   // 256 bit AES encryption key
-	std::string			   EncryptionIV;				   // 128 bit AES initialization vector
-	int					   BasePort				  = 1337;  // Service listen port (used for both UDP and TCP)
-	int					   OwnerPid				  = 0;	   // Parent process id (zero for standalone)
-	int					   WebSocketPort		  = 0;	   // Web socket port (Zero = disabled)
-	int					   WebSocketThreads		  = 0;
-	bool				   InstallService		  = false;	// Flag used to initiate service install (temporary)
-	bool				   UninstallService		  = false;	// Flag used to initiate service uninstall (temporary)
-	bool				   IsDebug				  = false;
-	bool				   IsTest				  = false;
-	bool				   IsDedicated			  = false;	// Indicates a dedicated/shared instance, with larger resource requirements
-	bool				   StructuredCacheEnabled = true;
-	bool				   StructuredCacheWriteLogEnabled  = false;
-	bool				   StructuredCacheAccessLogEnabled = false;
-	bool				   ExecServiceEnabled			   = true;
-	bool				   ComputeServiceEnabled		   = true;
-	bool				   ShouldCrash					   = false;	 // Option for testing crash handling
-	bool				   IsFirstRun					   = false;
-	bool				   NoSentry						   = false;
-	bool				   SentryAllowPII				   = false;	 // Allow personally identifiable information in sentry crash reports
-	bool				   ObjectStoreEnabled			   = false;
+	ZenUpstreamCacheConfig	 UpstreamCacheConfig;
+	ZenGcConfig				 GcConfig;
+	ZenAuthConfig			 AuthConfig;
+	ZenObjectStoreConfig	 ObjectStoreConfig;
+	zen::HttpServerConfig	 HttpServerConfig;
+	ZenStructuredCacheConfig StructuredCacheConfig;
+	std::filesystem::path	 DataDir;						// Root directory for state (used for testing)
+	std::filesystem::path	 ContentDir;					// Root directory for serving frontend content (experimental)
+	std::filesystem::path	 AbsLogFile;					// Absolute path to main log file
+	std::filesystem::path	 ConfigFile;					// Path to Lua config file
+	std::string				 ChildId;						// Id assigned by parent process (used for lifetime management)
+	std::string				 LogId;							// Id for tagging log output
+	std::string				 EncryptionKey;					// 256 bit AES encryption key
+	std::string				 EncryptionIV;					// 128 bit AES initialization vector
+	int						 BasePort			   = 1337;	// Service listen port (used for both UDP and TCP)
+	int						 OwnerPid			   = 0;		// Parent process id (zero for standalone)
+	int						 WebSocketPort		   = 0;		// Web socket port (Zero = disabled)
+	int						 WebSocketThreads	   = 0;
+	bool					 InstallService		   = false;	 // Flag used to initiate service install (temporary)
+	bool					 UninstallService	   = false;	 // Flag used to initiate service uninstall (temporary)
+	bool					 IsDebug			   = false;
+	bool					 IsTest				   = false;
+	bool					 IsDedicated		   = false;	 // Indicates a dedicated/shared instance, with larger resource requirements
+	bool					 ExecServiceEnabled	   = true;
+	bool					 ComputeServiceEnabled = true;
+	bool					 ShouldCrash		   = false;	 // Option for testing crash handling
+	bool					 IsFirstRun			   = false;
+	bool					 NoSentry			   = false;
+	bool					 SentryAllowPII		   = false;	 // Allow personally identifiable information in sentry crash reports
+	bool					 ObjectStoreEnabled	   = false;
 #if ZEN_WITH_TRACE
 	std::string TraceHost;	// Host name or IP address to send trace data to
 	std::string TraceFile;	// Path of a file to write a trace