structured compute basics (#714)

this change adds the `zencompute` component, which can be used to distribute work dispatched from UE using the DDB (Derived Data Build) APIs via zenserver

this change also adds a distinct zenserver compute mode (`zenserver compute`) which is intended to be used for leaf compute nodes

to exercise the compute functionality without directly involving UE, a `zen exec` subcommand is also added, which can be used to feed replays through the system

all new functionality is considered *experimental* and disabled by default at this time, behind the `zencompute` option in xmake config

1 files changed, 50 insertions, 5 deletions

diff --git a/src/zenserver/main.cpp b/src/zenserver/main.cpp
index 1a929b026..ee783d2a6 100644
--- a/src/zenserver/main.cpp
+++ b/src/zenserver/main.cpp
@@ -23,6 +23,9 @@
 #include <zenutil/service.h>
 
 #include "diag/logging.h"
+
+#include "compute/computeserver.h"
+
 #include "storage/storageconfig.h"
 #include "storage/zenstorageserver.h"
 
@@ -61,11 +64,19 @@ namespace zen {
 
 #if ZEN_PLATFORM_WINDOWS
 
-template<class T>
+/** Windows Service wrapper for Zen servers
+ *
+ * This class wraps a Zen server main entry point (the Main template parameter)
+ * into a Windows Service by implementing the WindowsService interface.
+ *
+ * The Main type needs to implement the virtual functions from the ZenServerMain
+ * base class, which provides the actual server logic.
+ */
+template<class Main>
 class ZenWindowsService : public WindowsService
 {
 public:
-	ZenWindowsService(typename T::Config& ServerOptions) : m_EntryPoint(ServerOptions) {}
+	ZenWindowsService(typename Main::Config& ServerOptions) : m_EntryPoint(ServerOptions) {}
 
 	ZenWindowsService(const ZenWindowsService&) = delete;
 	ZenWindowsService& operator=(const ZenWindowsService&) = delete;
@@ -73,7 +84,7 @@ public:
 	virtual int Run() override { return m_EntryPoint.Run(); }
 
 private:
-	T m_EntryPoint;
+	Main m_EntryPoint;
 };
 
 #endif	// ZEN_PLATFORM_WINDOWS
@@ -84,6 +95,23 @@ private:
 
 namespace zen {
 
+/** Application main entry point template
+ *
+ * This function handles common application startup tasks while allowing
+ * different server types to be plugged in via the Main template parameter.
+ *
+ * On Windows, this function also handles platform-specific service
+ * installation and uninstallation.
+ *
+ * The Main type needs to implement the virtual functions from the ZenServerMain
+ * base class, which provides the actual server logic.
+ *
+ * The Main type is also expected to provide the following members:
+ *
+ * typedef Config -- Server configuration type, derived from ZenServerConfig
+ * typedef Configurator -- Server configuration handler type, implements ZenServerConfiguratorBase
+ *
+ */
 template<class Main>
 int
 AppMain(int argc, char* argv[])
@@ -241,7 +269,12 @@ main(int argc, char* argv[])
 
 	auto _ = zen::MakeGuard([] {
 		// Allow some time for worker threads to unravel, in an effort
-		// to prevent shutdown races in TLS object destruction
+		// to prevent shutdown races in TLS object destruction, mainly due to
+		// threads which we don't directly control (Windows thread pool) and
+		// therefore can't join.
+		//
+		// This isn't a great solution, but for now it seems to help reduce
+		// shutdown crashes observed in some situations.
 		WaitForThreads(1000);
 	});
 
@@ -249,6 +282,7 @@ main(int argc, char* argv[])
 	{
 		kHub,
 		kStore,
+		kCompute,
 		kTest
 	} ServerMode = kStore;
 
@@ -258,10 +292,14 @@ main(int argc, char* argv[])
 		{
 			ServerMode = kHub;
 		}
-		else if (argv[1] == "store"sv)
+		else if ((argv[1] == "store"sv) || (argv[1] == "storage"sv))
 		{
 			ServerMode = kStore;
 		}
+		else if (argv[1] == "compute"sv)
+		{
+			ServerMode = kCompute;
+		}
 		else if (argv[1] == "test"sv)
 		{
 			ServerMode = kTest;
@@ -280,6 +318,13 @@ main(int argc, char* argv[])
 			break;
 		case kHub:
 			return AppMain<ZenHubServerMain>(argc, argv);
+		case kCompute:
+#if ZEN_WITH_COMPUTE_SERVICES
+			return AppMain<ZenComputeServerMain>(argc, argv);
+#else
+			fprintf(stderr, "compute services are not compiled in!\n");
+			exit(5);
+#endif
 		default:
 		case kStore:
 			return AppMain<ZenStorageServerMain>(argc, argv);