Lockfile implementation (#24)

Implemented lockfile synchronization

To be used instead of or in conjunction with existing events to coordinate launching and discovery of server instances

1 files changed, 62 insertions, 10 deletions

diff --git a/zenserver/zenserver.cpp b/zenserver/zenserver.cpp
index de30c5425..00abed513 100644
--- a/zenserver/zenserver.cpp
+++ b/zenserver/zenserver.cpp
@@ -8,11 +8,13 @@
 #include <zencore/logging.h>
 #include <zencore/refcount.h>
 #include <zencore/scopeguard.h>
+#include <zencore/session.h>
 #include <zencore/string.h>
 #include <zencore/thread.h>
 #include <zencore/timer.h>
 #include <zencore/windows.h>
 #include <zenhttp/httpserver.h>
+#include <zenstore/basicfile.h>
 #include <zenstore/cas.h>
 #include <zenstore/cidstore.h>
 #include <zenutil/zenserverprocess.h>
@@ -295,11 +297,13 @@ public:
 
 		const bool IsInteractiveMode = zen::IsInteractiveSession() && !m_TestMode;
 
-		m_CurrentState = kRunning;
+		SetNewState(kRunning);
+
+		OnReady();
 
 		m_Http->Run(IsInteractiveMode);
 
-		m_CurrentState = kShuttingDown;
+		SetNewState(kShuttingDown);
 
 		ZEN_INFO(ZEN_APP_NAME " exiting");
 
@@ -321,6 +325,10 @@ public:
 	void SetDataRoot(std::filesystem::path Root) { m_DataRoot = Root; }
 	void SetContentRoot(std::filesystem::path Root) { m_ContentRoot = Root; }
 
+	std::function<void()> m_IsReadyFunc;
+	void				  SetIsReadyFunc(std::function<void()>&& IsReadyFunc) { m_IsReadyFunc = std::move(IsReadyFunc); }
+	void				  OnReady();
+
 	void EnsureIoRunner()
 	{
 		if (!m_IoRunner.joinable())
@@ -434,6 +442,8 @@ private:
 		kShuttingDown
 	} m_CurrentState = kInitializing;
 
+	inline void SetNewState(ServerState NewState) { m_CurrentState = NewState; }
+
 	std::string_view ToString(ServerState Value)
 	{
 		switch (Value)
@@ -475,6 +485,17 @@ private:
 };
 
 void
+ZenServer::OnReady()
+{
+	m_ServerEntry->SignalReady();
+
+	if (m_IsReadyFunc)
+	{
+		m_IsReadyFunc();
+	}
+}
+
+void
 ZenServer::InitializeState(ZenServiceConfig& ServiceConfig)
 {
 	// Check root manifest to deal with schema versioning
@@ -681,6 +702,7 @@ public:
 private:
 	ZenServerOptions& m_GlobalOptions;
 	ZenServiceConfig& m_ServiceConfig;
+	zen::LockFile	  m_LockFile;
 };
 
 int
@@ -703,6 +725,32 @@ ZenWindowsService::Run()
 
 	try
 	{
+		// Mutual exclusion and synchronization
+
+		std::error_code Ec;
+
+		std::filesystem::path LockFilePath = GlobalOptions.DataDir / ".lock";
+
+		bool IsReady = false;
+
+		auto MakeLockData = [&] {
+			CbObjectWriter Cbo;
+			Cbo << "pid" << _getpid() << "data" << ToUtf8(GlobalOptions.DataDir) << "port" << GlobalOptions.BasePort << "session_id"
+				<< GetSessionId() << "ready" << IsReady;
+			return Cbo.Save();
+		};
+
+		m_LockFile.Create(LockFilePath, MakeLockData(), Ec);
+
+		if (Ec)
+		{
+			ConsoleLog().error("ERROR: Unable to grab lock at '{}' (error: '{}')", LockFilePath, Ec.message());
+
+			std::exit(99);
+		}
+
+		InitializeLogging(GlobalOptions);
+
 		// Prototype config system, we'll see how this pans out
 		//
 		// TODO: we need to report any parse errors here
@@ -764,13 +812,19 @@ ZenWindowsService::Run()
 		}});
 
 		// If we have a parent process, establish the mechanisms we need
-		// to be able to communicate with the parent
+		// to be able to communicate readiness with the parent
 
-		if (!GlobalOptions.ChildId.empty())
-		{
-			zen::NamedEvent ParentEvent{GlobalOptions.ChildId};
-			ParentEvent.Set();
-		}
+		Server.SetIsReadyFunc([&] {
+			IsReady = true;
+
+			m_LockFile.Update(MakeLockData(), Ec);
+
+			if (!GlobalOptions.ChildId.empty())
+			{
+				zen::NamedEvent ParentEvent{GlobalOptions.ChildId};
+				ParentEvent.Set();
+			}
+		});
 
 		Server.Run();
 		Server.Cleanup();
@@ -809,8 +863,6 @@ main(int argc, char* argv[])
 			std::filesystem::create_directories(GlobalOptions.DataDir);
 		}
 
-		InitializeLogging(GlobalOptions);
-
 #if ZEN_PLATFORM_WINDOWS
 		if (GlobalOptions.InstallService)
 		{