From 3e0f062df05a8ff6eff9b632e7c329a68390b762 Mon Sep 17 00:00:00 2001
From: Nick Bolton <nick@synergy-project.org>
Date: Sat, 14 Jul 2012 04:48:32 +0000
Subject: [PATCH] process stop detection and relaunch feature (useful for winxp
 where the server/client is killed at logout).

---
 src/lib/platform/CMSWindowsRelauncher.cpp | 38 +++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/src/lib/platform/CMSWindowsRelauncher.cpp b/src/lib/platform/CMSWindowsRelauncher.cpp
index e027a95e..29be85bc 100644
--- a/src/lib/platform/CMSWindowsRelauncher.cpp
+++ b/src/lib/platform/CMSWindowsRelauncher.cpp
@@ -257,6 +257,8 @@ CMSWindowsRelauncher::mainLoop(void*)
 	PROCESS_INFORMATION pi;
 	ZeroMemory(&pi, sizeof(PROCESS_INFORMATION));
 
+	int failures = 0;
+
 	while (m_running) {
 
 		HANDLE sendSasEvent = 0;
@@ -266,11 +268,42 @@ CMSWindowsRelauncher::mainLoop(void*)
 			sendSasEvent = CreateEvent(NULL, FALSE, FALSE, "Global\\SendSAS");
 		}
 
-		DWORD newSessionId = getSessionId();
+		DWORD newSessionId = getSessionId();
+
+		bool running = false;
+		if (launched) {
+
+			DWORD exitCode;
+			GetExitCodeProcess(pi.hProcess, &exitCode);
+			running = (exitCode == STILL_ACTIVE);
+
+			if (!running) {
+				failures++;
+				LOG((CLOG_INFO "detected application not running, pid=%d, failures=%d", pi.dwProcessId, failures));
+				
+				// increasing backoff period, maximum of 10 seconds.
+				int timeout = (failures * 2) < 10 ? (failures * 2) : 10;
+				LOG((CLOG_DEBUG "waiting, backoff period is %d seconds", timeout));
+				ARCH->sleep(timeout);
+				
+				// double check, in case process started after we waited.
+				GetExitCodeProcess(pi.hProcess, &exitCode);
+				running = (exitCode == STILL_ACTIVE);
+			}
+			else {
+				// reset failures when running.
+				failures = 0;
+			}
+		}
 
 		// only enter here when id changes, and the session isn't -1, which
 		// may mean that there is no active session.
-		if (((newSessionId != sessionId) && (newSessionId != -1)) || m_commandChanged) {
+		bool sessionChanged = ((newSessionId != sessionId) && (newSessionId != -1));
+
+		// relaunch if it was running but has stopped unexpectedly.
+		bool stoppedRunning = (launched && !running);
+
+		if (stoppedRunning || sessionChanged || m_commandChanged) {
 			
 			m_commandChanged = false;
 
@@ -328,6 +361,7 @@ CMSWindowsRelauncher::mainLoop(void*)
 						CREATE_UNICODE_ENVIRONMENT;
 
 					// re-launch in current active user session
+					LOG((CLOG_INFO "starting new process"));
 					BOOL createRet = CreateProcessAsUser(
 						userToken, NULL, LPSTR(cmd.c_str()),
 						&sa, NULL, TRUE, creationFlags,