Track and prioritize routing according to application restart generations

src/agent/Core/ApplicationPool/Group/InternalUtils.cpp

@@ -178,7 +178,7 @@ Group::createNullProcessObject() {
 	LockGuard l(context->memoryManagementSyncher);
 	Process *process = context->processObjectPool.malloc();
 	Guard guard(context, process);
-	process = new (process) Process(&info, args);
+	process = new (process) Process(&info, info.group->restartsInitiated, args);
 	process->shutdownNotRequired();
 	guard.clear();
 	return ProcessPtr(process, false);
@@ -215,7 +215,7 @@ Group::createProcessObject(const SpawningKit::Spawner &spawner,
 	LockGuard l(context->memoryManagementSyncher);
 	Process *process = context->processObjectPool.malloc();
 	Guard guard(context, process);
-	process = new (process) Process(&info, spawnResult, args);
+	process = new (process) Process(&info, info.group->restartsInitiated, spawnResult, args);
 	guard.clear();
 	return ProcessPtr(process, false);
 }

src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp

@@ -61,14 +61,20 @@ Process *
 Group::findProcessWithStickySessionIdOrLowestBusyness(unsigned int id) const {
 	int leastBusyProcessIndex = -1;
 	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size();
+	unsigned int i, size = enabledProcessBusynessLevels.size(), highest_gen = 0;
 	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
 
 	for (i = 0; i < size; i++) {
 		Process *process = enabledProcesses[i].get();
+        highest_gen = max(highest_gen, process->generation);
 		if (process->getStickySessionId() == id) {
 			return process;
-		} else if (leastBusyProcessIndex == -1 || enabledProcessBusynessLevels[i] < lowestBusyness) {
+                } else if (leastBusyProcessIndex == -1 ||
+                           enabledProcessBusynessLevels[i] < lowestBusyness ||
+						   (enabledProcessBusynessLevels[i] == lowestBusyness && process->generation > highest_gen)) {
+			if (process->generation > highest_gen) {
+				highest_gen = process->generation;
+			}
 			leastBusyProcessIndex = i;
 			lowestBusyness = enabledProcessBusynessLevels[i];
 		}
@@ -88,13 +94,19 @@ Group::findProcessWithLowestBusyness(const ProcessList &processes) const {
 	}
 
 	int lowestBusyness = -1;
+    unsigned int highest_gen = 0;
 	Process *leastBusyProcess = NULL;
 	ProcessList::const_iterator it;
 	ProcessList::const_iterator end = processes.end();
 	for (it = processes.begin(); it != end; it++) {
 		Process *process = (*it).get();
 		int busyness = process->busyness();
-		if (lowestBusyness == -1 || lowestBusyness > busyness) {
+		if (lowestBusyness == -1 ||
+			lowestBusyness > busyness ||
+			(busyness == lowestBusyness && process->generation > highest_gen)) {
+			if (process->generation > highest_gen) {
+				highest_gen = process->generation;
+			}
 			lowestBusyness = busyness;
 			leastBusyProcess = process;
 		}
@@ -113,11 +125,16 @@ Group::findEnabledProcessWithLowestBusyness() const {
 
 	int leastBusyProcessIndex = -1;
 	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size();
+	unsigned int i, size = enabledProcessBusynessLevels.size(), highest_gen = 0;
 	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
 
 	for (i = 0; i < size; i++) {
-		if (leastBusyProcessIndex == -1 || enabledProcessBusynessLevels[i] < lowestBusyness) {
+		if (leastBusyProcessIndex == -1 ||
+			enabledProcessBusynessLevels[i] < lowestBusyness ||
+			(enabledProcessBusynessLevels[i] == lowestBusyness && enabledProcesses[i]->generation > highest_gen)) {
+			if (enabledProcesses[i]->generation > highest_gen) {
+				highest_gen = enabledProcesses[i]->generation;
+			}
 			leastBusyProcessIndex = i;
 			lowestBusyness = enabledProcessBusynessLevels[i];
 		}

src/agent/Core/ApplicationPool/Process.h

@@ -384,6 +384,10 @@ class Process {
 
 	/** Last time when a session was opened for this Process. */
 	unsigned long long lastUsed;
+    /** Which gereration of app processes this one belongs to,
+        inherited from the app group, incremented when a restart
+		is initiated*/
+	const unsigned int generation;
 	/** Number of sessions currently open.
 	 * @invariant session >= 0
 	 */
@@ -446,8 +450,7 @@ class Process {
 	/** Collected by Pool::collectAnalytics(). */
 	ProcessMetrics metrics;
 
-
-	Process(const BasicGroupInfo *groupInfo, const Json::Value &args)
+	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const Json::Value &args)
 		: info(this, groupInfo, args),
 		  socketsAcceptingHttpRequestsCount(0),
 		  spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
@@ -458,6 +461,7 @@ class Process {
 		  refcount(1),
 		  index(-1),
 		  lastUsed(spawnEndTime),
+		  generation(gen),
 		  sessions(0),
 		  processed(0),
 		  lifeStatus(ALIVE),
@@ -471,7 +475,7 @@ class Process {
 		indexSocketsAcceptingHttpRequests();
 	}
 
-	Process(const BasicGroupInfo *groupInfo, const SpawningKit::Result &skResult,
+	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const SpawningKit::Result &skResult,
 		const Json::Value &args)
 		: info(this, groupInfo, skResult),
 		  socketsAcceptingHttpRequestsCount(0),
@@ -483,6 +487,7 @@ class Process {
 		  refcount(1),
 		  index(-1),
 		  lastUsed(spawnEndTime),
+		  generation(gen),
 		  sessions(0),
 		  processed(0),
 		  lifeStatus(ALIVE),

test/cxx/Core/ApplicationPool/ProcessTest.cpp

@@ -118,8 +118,10 @@ namespace tut {
 
 			args["spawner_creation_time"] = 0;
 
-			ProcessPtr process(context.processObjectPool.construct(
-				&groupInfo, result, args), false);
+			Process *p = context.processObjectPool.malloc();
+			p = new (p) Process(&groupInfo, 0, result, args);
+			ProcessPtr process(p, false);
+
 			process->shutdownNotRequired();
 			return process;
 		}