From 20df215e637491b366f80db325bc36da7531fbd3 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 9 Sep 2024 10:46:04 -0600
Subject: [PATCH 01/20] add generation field to process

---
 .../Core/ApplicationPool/Group/InternalUtils.cpp      |  4 ++--
 src/agent/Core/ApplicationPool/Process.h              | 11 ++++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/InternalUtils.cpp b/src/agent/Core/ApplicationPool/Group/InternalUtils.cpp
index 034e43ce31..d8250332ad 100644
--- a/src/agent/Core/ApplicationPool/Group/InternalUtils.cpp
+++ b/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);
 }
diff --git a/src/agent/Core/ApplicationPool/Process.h b/src/agent/Core/ApplicationPool/Process.h
index cd91f2e0e9..c5ad2700ae 100644
--- a/src/agent/Core/ApplicationPool/Process.h
+++ b/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),

From 744c2b289330fba25332cdfc2c832248dadf3122 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 9 Sep 2024 11:18:28 -0600
Subject: [PATCH 02/20] use process generation to inform routing

---
 .../Group/ProcessListManagement.cpp           | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 94438ff766..88584b1b75 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/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 +125,13 @@ 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)) {
 			leastBusyProcessIndex = i;
 			lowestBusyness = enabledProcessBusynessLevels[i];
 		}

From b5dd97a9a981bd3395c018676e9c3fb3a0f6573e Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 9 Sep 2024 14:40:30 -0600
Subject: [PATCH 03/20] missed changes

---
 .../Core/ApplicationPool/Group/ProcessListManagement.cpp    | 3 +++
 test/cxx/Core/ApplicationPool/ProcessTest.cpp               | 6 ++++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 88584b1b75..c3a1aa5d46 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -132,6 +132,9 @@ Group::findEnabledProcessWithLowestBusyness() const {
 		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];
 		}
diff --git a/test/cxx/Core/ApplicationPool/ProcessTest.cpp b/test/cxx/Core/ApplicationPool/ProcessTest.cpp
index 6e6518677b..b9d6c0727b 100644
--- a/test/cxx/Core/ApplicationPool/ProcessTest.cpp
+++ b/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;
 		}

From df6f2ac3bd0abb25007b8504cad59f521cc80a69 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Sun, 22 Sep 2024 13:58:35 -0600
Subject: [PATCH 04/20] address feedback

---
 .../Group/ProcessListManagement.cpp           | 29 +++++++------------
 1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index c3a1aa5d46..72124c7530 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -61,20 +61,17 @@ Process *
 Group::findProcessWithStickySessionIdOrLowestBusyness(unsigned int id) const {
 	int leastBusyProcessIndex = -1;
 	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size(), highest_gen = 0;
+	unsigned int i, size = enabledProcessBusynessLevels.size(), highestGeneration = 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 ||
-						   (enabledProcessBusynessLevels[i] == lowestBusyness && process->generation > highest_gen)) {
-			if (process->generation > highest_gen) {
-				highest_gen = process->generation;
-			}
+        } else if (leastBusyProcessIndex == -1 ||
+                   enabledProcessBusynessLevels[i] < lowestBusyness ||
+				   (enabledProcessBusynessLevels[i] == lowestBusyness && process->generation > highestGeneration)) {
+			highestGeneration = std::max(highestGeneration, process->generation);
 			leastBusyProcessIndex = i;
 			lowestBusyness = enabledProcessBusynessLevels[i];
 		}
@@ -94,7 +91,7 @@ Group::findProcessWithLowestBusyness(const ProcessList &processes) const {
 	}
 
 	int lowestBusyness = -1;
-    unsigned int highest_gen = 0;
+    unsigned int highestGeneration = 0;
 	Process *leastBusyProcess = NULL;
 	ProcessList::const_iterator it;
 	ProcessList::const_iterator end = processes.end();
@@ -103,10 +100,8 @@ Group::findProcessWithLowestBusyness(const ProcessList &processes) const {
 		int busyness = process->busyness();
 		if (lowestBusyness == -1 ||
 			lowestBusyness > busyness ||
-			(busyness == lowestBusyness && process->generation > highest_gen)) {
-			if (process->generation > highest_gen) {
-				highest_gen = process->generation;
-			}
+			(busyness == lowestBusyness && process->generation > highestGeneration)) {
+			highestGeneration = std::max(highestGeneration, process->generation);
 			lowestBusyness = busyness;
 			leastBusyProcess = process;
 		}
@@ -125,16 +120,14 @@ Group::findEnabledProcessWithLowestBusyness() const {
 
 	int leastBusyProcessIndex = -1;
 	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size(), highest_gen = 0;
+	unsigned int i, size = enabledProcessBusynessLevels.size(), highestGeneration = 0;
 	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
 
 	for (i = 0; i < size; i++) {
 		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;
-			}
+			(enabledProcessBusynessLevels[i] == lowestBusyness && enabledProcesses[i]->generation > highestGeneration)) {
+			highestGeneration = std::max(highestGeneration, enabledProcesses[i]->generation);
 			leastBusyProcessIndex = i;
 			lowestBusyness = enabledProcessBusynessLevels[i];
 		}

From 38187b22dd1cbd6f1fb1e34a4933e2c6281d2f59 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Sun, 22 Sep 2024 14:40:02 -0600
Subject: [PATCH 05/20] add a test to process test suite
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

not that there’s a point in this test really
---
 test/cxx/Core/ApplicationPool/ProcessTest.cpp | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/test/cxx/Core/ApplicationPool/ProcessTest.cpp b/test/cxx/Core/ApplicationPool/ProcessTest.cpp
index b9d6c0727b..e90f2fb1a0 100644
--- a/test/cxx/Core/ApplicationPool/ProcessTest.cpp
+++ b/test/cxx/Core/ApplicationPool/ProcessTest.cpp
@@ -14,6 +14,7 @@ namespace tut {
 		SpawningKit::Context skContext;
 		Context context;
 		BasicGroupInfo groupInfo;
+		unsigned int generation;
 		vector<SpawningKit::Result::Socket> sockets;
 		Pipe stdinFd, stdoutAndErrFd;
 		FileDescriptor server1, server2, server3;
@@ -34,6 +35,8 @@ namespace tut {
 			groupInfo.group = NULL;
 			groupInfo.name = "test";
 
+			generation = 0;
+
 			struct sockaddr_in addr;
 			socklen_t len = sizeof(addr);
 			SpawningKit::Result::Socket socket;
@@ -119,7 +122,7 @@ namespace tut {
 			args["spawner_creation_time"] = 0;
 
 			Process *p = context.processObjectPool.malloc();
-			p = new (p) Process(&groupInfo, 0, result, args);
+			p = new (p) Process(&groupInfo, generation, result, args);
 			ProcessPtr process(p, false);
 
 			process->shutdownNotRequired();
@@ -240,4 +243,15 @@ namespace tut {
 				&& contents.find("stdout and err 4\n") != string::npos;
 		);
 	}
+
+    TEST_METHOD(6) {
+        set_test_name("Test generation is inherited from pool at construction time");
+	    // this test is pointless b/c the process is made at line 123 of this file, not in the regular codebase
+	    ProcessPtr process1 = createProcess();
+		ensure_equals(process1->generation, generation);
+		generation++;
+		ProcessPtr process2 = createProcess();
+		ensure_equals(process2->generation, generation);
+		ensure(process1->generation != process2->generation);
+    }
 }

From a376e8eb6317565626ed60ce385c16507ab1fb82 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 23 Sep 2024 14:58:53 -0600
Subject: [PATCH 06/20] add another test

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 32 +++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index c2bc70a65d..a4be14c735 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -5,7 +5,6 @@
 #include <FileTools/FileManip.h>
 #include <StrIntTools/StrIntUtils.h>
 #include <IOTools/MessageSerialization.h>
-#include <map>
 #include <vector>
 #include <cerrno>
 #include <signal.h>
@@ -632,6 +631,37 @@ namespace tut {
 		ensure_equals(pool->getGroupCount(), 0u);
 	}
 
+	TEST_METHOD(15) {
+	    // Test that the process generation increments when the group restarts
+		Options options = createOptions();
+
+		// Spawn a process and opens a session with it.
+		pool->setMax(1);
+		pool->asyncGet(options, callback);
+		EVENTUALLY(5,
+			result = number == 1;
+		);
+
+		// Close the session so that the process is now idle.
+		ProcessPtr process = currentSession->getProcess()->shared_from_this();
+		currentSession.reset();
+		unsigned int gen1 = process->generation;
+
+		ensure(pool->restartGroupByName(options.appRoot));
+		EVENTUALLY(5,
+			result = pool->getProcessCount() == 1;
+		);
+		pool->asyncGet(options, callback);
+		EVENTUALLY(5,
+			result = number == 2;
+		);
+
+		process = currentSession->getProcess()->shared_from_this();
+		currentSession.reset();
+		unsigned int gen2 = process->generation;
+		ensure_equals(gen1+1,gen2);
+	}
+
 	TEST_METHOD(17) {
 		// Test that restartGroupByName() spawns more processes to ensure
 		// that minProcesses and other constraints are met.

From 824166d14a8fa8fee71bd9c2ca478236db5c9801 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 23 Sep 2024 15:34:09 -0600
Subject: [PATCH 07/20] test stub for proper testing of routing algo

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index a4be14c735..3bb0e4ce44 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -662,6 +662,35 @@ namespace tut {
 		ensure_equals(gen1+1,gen2);
 	}
 
+	TEST_METHOD(16) {
+	    // Test that the correct process from the pool is routed
+		Options options = createOptions();
+		ensureMinProcesses(2);
+
+		// async restart the group
+		ensure(pool->restartGroupByName(options.appRoot));
+		ensureMinProcesses(1);
+
+        /*
+		  Imagine we have these processes (ordered from oldest to newest):
+
+          #. PID 1 (generation A, busyness 5)
+          #. PID 2 (generation A, busyness 3)
+          #. PID 3 (generation B, busyness 1)
+
+          The algorithm should select PID 3
+		 */
+
+		/*
+		  Imagine we have these processes (ordered from oldest to newest):
+
+          #. PID 1 (generation A, busyness 1)
+          #. PID 2 (generation B, busyness 5)
+
+          The algorithm should select PID 1
+		 */
+	}
+
 	TEST_METHOD(17) {
 		// Test that restartGroupByName() spawns more processes to ensure
 		// that minProcesses and other constraints are met.

From 60d254b57202cfb8671f7cf20d34d885c45f5035 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Fri, 27 Sep 2024 13:41:12 -0600
Subject: [PATCH 08/20] impl new algo

---
 src/agent/Core/ApplicationPool/Group.h        |  6 +-
 .../Group/ProcessListManagement.cpp           | 94 +++++++++----------
 .../Group/SessionManagement.cpp               |  8 +-
 src/agent/Core/ApplicationPool/Process.h      | 21 ++---
 4 files changed, 64 insertions(+), 65 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group.h b/src/agent/Core/ApplicationPool/Group.h
index fba45f8091..9f7362a1d4 100644
--- a/src/agent/Core/ApplicationPool/Group.h
+++ b/src/agent/Core/ApplicationPool/Group.h
@@ -223,9 +223,9 @@ class Group: public boost::enable_shared_from_this<Group> {
 	/****** Process list management ******/
 
 	Process *findProcessWithStickySessionId(unsigned int id) const;
-	Process *findProcessWithStickySessionIdOrLowestBusyness(unsigned int id) const;
-	Process *findProcessWithLowestBusyness(const ProcessList &processes) const;
-	Process *findEnabledProcessWithLowestBusyness() const;
+	Process *findBestProcessPreferringStickySessionId(unsigned int id) const;
+	Process *findBestProcess(const ProcessList &processes) const;
+	Process *findBestEnabledProcess() const;
 
 	void addProcessToList(const ProcessPtr &process, ProcessList &destination);
 	void removeProcessFromList(const ProcessPtr &process, ProcessList &source);
diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 72124c7530..0c0544d52f 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -58,81 +58,81 @@ Group::findProcessWithStickySessionId(unsigned int id) const {
 }
 
 Process *
-Group::findProcessWithStickySessionIdOrLowestBusyness(unsigned int id) const {
-	int leastBusyProcessIndex = -1;
-	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size(), highestGeneration = 0;
-	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
-
-	for (i = 0; i < size; i++) {
-		Process *process = enabledProcesses[i].get();
+Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
+	Process *bestProcess = nullptr;
+	ProcessList::const_iterator it;
+	ProcessList::const_iterator end = enabledProcesses.end();
+	for (it = enabledProcesses.begin(); it != end; it++) {
+		Process *process = (*it).get();
 		if (process->getStickySessionId() == id) {
 			return process;
-        } else if (leastBusyProcessIndex == -1 ||
-                   enabledProcessBusynessLevels[i] < lowestBusyness ||
-				   (enabledProcessBusynessLevels[i] == lowestBusyness && process->generation > highestGeneration)) {
-			highestGeneration = std::max(highestGeneration, process->generation);
-			leastBusyProcessIndex = i;
-			lowestBusyness = enabledProcessBusynessLevels[i];
+        } else if (bestProcess == nullptr ||
+                   process->generation > bestProcess->generation ||
+				   (process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
+				   (process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
+        ) {
+			bestProcess = process;
 		}
 	}
-
-	if (leastBusyProcessIndex == -1) {
-		return NULL;
-	} else {
-		return enabledProcesses[leastBusyProcessIndex].get();
-	}
+	return bestProcess;
 }
 
 Process *
-Group::findProcessWithLowestBusyness(const ProcessList &processes) const {
+Group::findBestProcess(const ProcessList &processes) const {
 	if (processes.empty()) {
-		return NULL;
+		return nullptr;
 	}
 
-	int lowestBusyness = -1;
-    unsigned int highestGeneration = 0;
-	Process *leastBusyProcess = NULL;
+	Process *bestProcess = nullptr;
 	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 ||
-			(busyness == lowestBusyness && process->generation > highestGeneration)) {
-			highestGeneration = std::max(highestGeneration, process->generation);
-			lowestBusyness = busyness;
-			leastBusyProcess = process;
+
+		if (bestProcess == nullptr ||
+			process->generation > bestProcess->generation ||
+			(process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
+			(process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
+        ) {
+			bestProcess = process;
 		}
 	}
-	return leastBusyProcess;
+	return bestProcess;
 }
 
 /**
- * Cache-optimized version of findProcessWithLowestBusyness() for the common case.
+ * Cache-optimized version of findBestProcess() for the common case.
  */
 Process *
-Group::findEnabledProcessWithLowestBusyness() const {
+Group::findBestEnabledProcess() const {
 	if (enabledProcesses.empty()) {
-		return NULL;
+		return nullptr;
 	}
 
-	int leastBusyProcessIndex = -1;
-	int lowestBusyness = 0;
-	unsigned int i, size = enabledProcessBusynessLevels.size(), highestGeneration = 0;
+	Process* bestProcess = nullptr;
+	unsigned long long bestProcessStartTime = 0;
+	unsigned int bestProcessGen = 0;
+	int bestProcessBusyness = 0;
+	unsigned int size = enabledProcessBusynessLevels.size();
 	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
 
-	for (i = 0; i < size; i++) {
-		if (leastBusyProcessIndex == -1 ||
-			enabledProcessBusynessLevels[i] < lowestBusyness ||
-			(enabledProcessBusynessLevels[i] == lowestBusyness && enabledProcesses[i]->generation > highestGeneration)) {
-			highestGeneration = std::max(highestGeneration, enabledProcesses[i]->generation);
-			leastBusyProcessIndex = i;
-			lowestBusyness = enabledProcessBusynessLevels[i];
+	for (unsigned int i = 0; i < size; i++) {
+		Process *process = enabledProcesses.at(i).get();
+		unsigned int gen = process->generation;
+		unsigned long long startTime = process->spawnerCreationTime;
+		int busyness = enabledProcessBusynessLevels[i];
+		if (bestProcess == nullptr ||
+ 			gen > bestProcess->generation ||
+			(gen == bestProcessGen && startTime <  bestProcessStartTime) ||
+			(gen == bestProcessGen && startTime == bestProcessStartTime && busyness < bestProcessBusyness)
+		) {
+			bestProcess = process;
+			bestProcessGen = gen;
+			bestProcessBusyness = busyness;
+			bestProcessStartTime = startTime;
 		}
 	}
-	return enabledProcesses[leastBusyProcessIndex].get();
+	return bestProcess;
 }
 
 /**
diff --git a/src/agent/Core/ApplicationPool/Group/SessionManagement.cpp b/src/agent/Core/ApplicationPool/Group/SessionManagement.cpp
index a9e9510077..be17dca6c3 100644
--- a/src/agent/Core/ApplicationPool/Group/SessionManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/SessionManagement.cpp
@@ -58,14 +58,14 @@ Group::RouteResult
 Group::route(const Options &options) const {
 	if (OXT_LIKELY(enabledCount > 0)) {
 		if (options.stickySessionId == 0) {
-			Process *process = findEnabledProcessWithLowestBusyness();
+			Process *process = findBestEnabledProcess();
 			if (process->canBeRoutedTo()) {
 				return RouteResult(process);
 			} else {
 				return RouteResult(NULL, true);
 			}
 		} else {
-			Process *process = findProcessWithStickySessionIdOrLowestBusyness(
+			Process *process = findBestProcessPreferringStickySessionId(
 				options.stickySessionId);
 			if (process != NULL) {
 				if (process->canBeRoutedTo()) {
@@ -78,7 +78,7 @@ Group::route(const Options &options) const {
 			}
 		}
 	} else {
-		Process *process = findProcessWithLowestBusyness(disablingProcesses);
+		Process *process = findBestProcess(disablingProcesses);
 		if (process->canBeRoutedTo()) {
 			return RouteResult(process);
 		} else {
@@ -304,7 +304,7 @@ Group::get(const Options &newOptions, const GetCallback &callback,
 		assert(m_spawning || restarting() || poolAtFullCapacity());
 
 		if (disablingCount > 0 && !restarting()) {
-			Process *process = findProcessWithLowestBusyness(disablingProcesses);
+			Process *process = findBestProcess(disablingProcesses);
 			assert(process != NULL);
 			if (!process->isTotallyBusy()) {
 				return newSession(process, newOptions.currentTime);
diff --git a/src/agent/Core/ApplicationPool/Process.h b/src/agent/Core/ApplicationPool/Process.h
index c5ad2700ae..611a384fd5 100644
--- a/src/agent/Core/ApplicationPool/Process.h
+++ b/src/agent/Core/ApplicationPool/Process.h
@@ -28,7 +28,6 @@
 
 #include <string>
 #include <vector>
-#include <algorithm>
 #include <boost/intrusive_ptr.hpp>
 #include <boost/move/core.hpp>
 #include <boost/container/vector.hpp>
@@ -102,6 +101,12 @@ class Process {
 public:
 	static const unsigned int MAX_SOCKETS_ACCEPTING_HTTP_REQUESTS = 3;
 
+	/**
+	 * Time at which the Spawner that created this process was created.
+	 * Microseconds resolution.
+	 */
+	unsigned long long spawnerCreationTime;
+
 private:
 	/*************************************************************
 	 * Read-only fields, set once during initialization and never
@@ -141,12 +146,6 @@ class Process {
 	 */
 	StaticString codeRevision;
 
-	/**
-	 * Time at which the Spawner that created this process was created.
-	 * Microseconds resolution.
-	 */
-	unsigned long long spawnerCreationTime;
-
 	/** Time at which we started spawning this process. Microseconds resolution. */
 	unsigned long long spawnStartTime;
 
@@ -451,9 +450,9 @@ class Process {
 	ProcessMetrics metrics;
 
 	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const Json::Value &args)
-		: info(this, groupInfo, args),
+		: spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
+		  info(this, groupInfo, args),
 		  socketsAcceptingHttpRequestsCount(0),
-		  spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
 		  spawnStartTime(getJsonUint64Field(args, "spawn_start_time")),
 		  spawnEndTime(SystemTime::getUsec()),
 		  type(args["type"] == "dummy" ? SpawningKit::Result::DUMMY : SpawningKit::Result::UNKNOWN),
@@ -477,9 +476,9 @@ class Process {
 
 	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const SpawningKit::Result &skResult,
 		const Json::Value &args)
-		: info(this, groupInfo, skResult),
+		: spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
+		  info(this, groupInfo, skResult),
 		  socketsAcceptingHttpRequestsCount(0),
-		  spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
 		  spawnStartTime(skResult.spawnStartTime),
 		  spawnEndTime(skResult.spawnEndTime),
 		  type(skResult.type),

From 6b739f36bda65b11e93800735139227fe7979e6c Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Sun, 29 Sep 2024 22:31:37 -0600
Subject: [PATCH 09/20] update changelog

[ci skip] [ci:skip]
---
 CHANGELOG | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG b/CHANGELOG
index 3e1ee91260..f322903a7f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 Release 6.0.24 (Not yet released)
 -------------
- *
+ * Update the order Passenger routes requests to app processes. Processes are now chosen based on being in the latest generation (Enterprise), then by newest process, then by oldest, then by
+busyness. Closes GH-2551.
 
 
 Release 6.0.23

From fd217749bbdd2c77b694c4ccc0e8bc4aba4da6d0 Mon Sep 17 00:00:00 2001
From: "Hongli Lai (Phusion)" <hongli@phusion.nl>
Date: Thu, 3 Oct 2024 15:51:20 +0200
Subject: [PATCH 10/20] Fix indentation

---
 .../Core/ApplicationPool/Group/ProcessListManagement.cpp  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 0c0544d52f..5d5e304bfa 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -66,11 +66,11 @@ Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
 		Process *process = (*it).get();
 		if (process->getStickySessionId() == id) {
 			return process;
-        } else if (bestProcess == nullptr ||
-                   process->generation > bestProcess->generation ||
+		} else if (bestProcess == nullptr ||
+				   process->generation > bestProcess->generation ||
 				   (process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
 				   (process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
-        ) {
+		) {
 			bestProcess = process;
 		}
 	}
@@ -93,7 +93,7 @@ Group::findBestProcess(const ProcessList &processes) const {
 			process->generation > bestProcess->generation ||
 			(process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
 			(process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
-        ) {
+		) {
 			bestProcess = process;
 		}
 	}

From c0d99a6ef4081e8a96cd4d78e7a8ca382c48f05f Mon Sep 17 00:00:00 2001
From: "Hongli Lai (Phusion)" <hongli@phusion.nl>
Date: Thu, 3 Oct 2024 16:42:34 +0200
Subject: [PATCH 11/20] Remove the new test in ProcessTest.cpp because it's
 pointless

---
 test/cxx/Core/ApplicationPool/ProcessTest.cpp | 17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff --git a/test/cxx/Core/ApplicationPool/ProcessTest.cpp b/test/cxx/Core/ApplicationPool/ProcessTest.cpp
index e90f2fb1a0..a3d508cd06 100644
--- a/test/cxx/Core/ApplicationPool/ProcessTest.cpp
+++ b/test/cxx/Core/ApplicationPool/ProcessTest.cpp
@@ -14,7 +14,6 @@ namespace tut {
 		SpawningKit::Context skContext;
 		Context context;
 		BasicGroupInfo groupInfo;
-		unsigned int generation;
 		vector<SpawningKit::Result::Socket> sockets;
 		Pipe stdinFd, stdoutAndErrFd;
 		FileDescriptor server1, server2, server3;
@@ -35,8 +34,6 @@ namespace tut {
 			groupInfo.group = NULL;
 			groupInfo.name = "test";
 
-			generation = 0;
-
 			struct sockaddr_in addr;
 			socklen_t len = sizeof(addr);
 			SpawningKit::Result::Socket socket;
@@ -122,9 +119,8 @@ namespace tut {
 			args["spawner_creation_time"] = 0;
 
 			Process *p = context.processObjectPool.malloc();
-			p = new (p) Process(&groupInfo, generation, result, args);
+			p = new (p) Process(&groupInfo, 0, result, args);
 			ProcessPtr process(p, false);
-
 			process->shutdownNotRequired();
 			return process;
 		}
@@ -243,15 +239,4 @@ namespace tut {
 				&& contents.find("stdout and err 4\n") != string::npos;
 		);
 	}
-
-    TEST_METHOD(6) {
-        set_test_name("Test generation is inherited from pool at construction time");
-	    // this test is pointless b/c the process is made at line 123 of this file, not in the regular codebase
-	    ProcessPtr process1 = createProcess();
-		ensure_equals(process1->generation, generation);
-		generation++;
-		ProcessPtr process2 = createProcess();
-		ensure_equals(process2->generation, generation);
-		ensure(process1->generation != process2->generation);
-    }
 }

From f8481e1dc254074de85a73e085d5047eac08083a Mon Sep 17 00:00:00 2001
From: "Hongli Lai (Phusion)" <hongli@phusion.nl>
Date: Thu, 3 Oct 2024 16:44:45 +0200
Subject: [PATCH 12/20] Fix typo, set test name

---
 src/agent/Core/ApplicationPool/Process.h   | 2 +-
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Process.h b/src/agent/Core/ApplicationPool/Process.h
index 611a384fd5..0685e367a0 100644
--- a/src/agent/Core/ApplicationPool/Process.h
+++ b/src/agent/Core/ApplicationPool/Process.h
@@ -383,7 +383,7 @@ 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,
+    /** Which generation of app processes this one belongs to,
         inherited from the app group, incremented when a restart
 		is initiated*/
 	const unsigned int generation;
diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index 3bb0e4ce44..9a86b3ff86 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -632,7 +632,7 @@ namespace tut {
 	}
 
 	TEST_METHOD(15) {
-	    // Test that the process generation increments when the group restarts
+	    set_test_name("Process generation increments when the group restarts");
 		Options options = createOptions();
 
 		// Spawn a process and opens a session with it.

From 6ab1b52d6d9c8c4885dda8c8932626c5ed4a3902 Mon Sep 17 00:00:00 2001
From: "Hongli Lai (Phusion)" <hongli@phusion.nl>
Date: Thu, 3 Oct 2024 16:55:09 +0200
Subject: [PATCH 13/20] Use spawnStartTime instead of spawnerCreationTime

---
 .../Group/ProcessListManagement.cpp           | 10 ++++-----
 src/agent/Core/ApplicationPool/Process.h      | 22 ++++++++++---------
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 5d5e304bfa..8020020417 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -68,8 +68,8 @@ Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
 			return process;
 		} else if (bestProcess == nullptr ||
 				   process->generation > bestProcess->generation ||
-				   (process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
-				   (process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
+				   (process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
+				   (process->generation == bestProcess->generation && process->spawnStartTime == bestProcess->spawnStartTime && process->busyness() < bestProcess->busyness())
 		) {
 			bestProcess = process;
 		}
@@ -91,8 +91,8 @@ Group::findBestProcess(const ProcessList &processes) const {
 
 		if (bestProcess == nullptr ||
 			process->generation > bestProcess->generation ||
-			(process->generation == bestProcess->generation && process->spawnerCreationTime < bestProcess->spawnerCreationTime) ||
-			(process->generation == bestProcess->generation && process->spawnerCreationTime == bestProcess->spawnerCreationTime && process->busyness() < bestProcess->busyness())
+			(process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
+			(process->generation == bestProcess->generation && process->spawnStartTime == bestProcess->spawnStartTime && process->busyness() < bestProcess->busyness())
 		) {
 			bestProcess = process;
 		}
@@ -119,7 +119,7 @@ Group::findBestEnabledProcess() const {
 	for (unsigned int i = 0; i < size; i++) {
 		Process *process = enabledProcesses.at(i).get();
 		unsigned int gen = process->generation;
-		unsigned long long startTime = process->spawnerCreationTime;
+		unsigned long long startTime = process->spawnStartTime;
 		int busyness = enabledProcessBusynessLevels[i];
 		if (bestProcess == nullptr ||
  			gen > bestProcess->generation ||
diff --git a/src/agent/Core/ApplicationPool/Process.h b/src/agent/Core/ApplicationPool/Process.h
index 0685e367a0..7275402d6d 100644
--- a/src/agent/Core/ApplicationPool/Process.h
+++ b/src/agent/Core/ApplicationPool/Process.h
@@ -99,13 +99,9 @@ typedef boost::container::vector<ProcessPtr> ProcessList;
  */
 class Process {
 public:
-	static const unsigned int MAX_SOCKETS_ACCEPTING_HTTP_REQUESTS = 3;
+	friend class Group;
 
-	/**
-	 * Time at which the Spawner that created this process was created.
-	 * Microseconds resolution.
-	 */
-	unsigned long long spawnerCreationTime;
+	static const unsigned int MAX_SOCKETS_ACCEPTING_HTTP_REQUESTS = 3;
 
 private:
 	/*************************************************************
@@ -146,6 +142,12 @@ class Process {
 	 */
 	StaticString codeRevision;
 
+	/**
+	 * Time at which the Spawner that created this process was created.
+	 * Microseconds resolution.
+	 */
+	unsigned long long spawnerCreationTime;
+
 	/** Time at which we started spawning this process. Microseconds resolution. */
 	unsigned long long spawnStartTime;
 
@@ -450,9 +452,9 @@ class Process {
 	ProcessMetrics metrics;
 
 	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const Json::Value &args)
-		: spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
-		  info(this, groupInfo, args),
+		: info(this, groupInfo, args),
 		  socketsAcceptingHttpRequestsCount(0),
+		  spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
 		  spawnStartTime(getJsonUint64Field(args, "spawn_start_time")),
 		  spawnEndTime(SystemTime::getUsec()),
 		  type(args["type"] == "dummy" ? SpawningKit::Result::DUMMY : SpawningKit::Result::UNKNOWN),
@@ -476,9 +478,9 @@ class Process {
 
 	Process(const BasicGroupInfo *groupInfo, const unsigned int gen, const SpawningKit::Result &skResult,
 		const Json::Value &args)
-		: spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
-		  info(this, groupInfo, skResult),
+		: info(this, groupInfo, skResult),
 		  socketsAcceptingHttpRequestsCount(0),
+		  spawnerCreationTime(getJsonUint64Field(args, "spawner_creation_time")),
 		  spawnStartTime(skResult.spawnStartTime),
 		  spawnEndTime(skResult.spawnEndTime),
 		  type(skResult.type),

From cec763864668a8ca2d9987126120e92b176c8e86 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 14 Oct 2024 13:13:38 -0600
Subject: [PATCH 14/20] remove unused headers

---
 src/agent/Core/ApplicationPool/Pool.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Pool.h b/src/agent/Core/ApplicationPool/Pool.h
index 16ee56f928..e2c727db7f 100644
--- a/src/agent/Core/ApplicationPool/Pool.h
+++ b/src/agent/Core/ApplicationPool/Pool.h
@@ -28,10 +28,8 @@
 
 #include <string>
 #include <vector>
-#include <algorithm>
 #include <utility>
 #include <sstream>
-#include <iomanip>
 #include <boost/thread.hpp>
 #include <boost/bind/bind.hpp>
 #include <boost/shared_ptr.hpp>

From a45c981a935e1d70e83a413f20d3b76af2b774ae Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 14 Oct 2024 13:16:55 -0600
Subject: [PATCH 15/20] =?UTF-8?q?change=20test=20condition=20per=20hongli?=
 =?UTF-8?q?=E2=80=99s=20request?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index 9a86b3ff86..bdda8bc6b6 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -644,12 +644,15 @@ namespace tut {
 
 		// Close the session so that the process is now idle.
 		ProcessPtr process = currentSession->getProcess()->shared_from_this();
+		pid_t pid = process->getPid();
 		currentSession.reset();
 		unsigned int gen1 = process->generation;
 
 		ensure(pool->restartGroupByName(options.appRoot));
 		EVENTUALLY(5,
-			result = pool->getProcessCount() == 1;
+				   LockGuard l(pool->syncher);
+				   vector<ProcessPtr> processes = pool->getProcesses(false);
+				   processes.size() > 0 && processes[0]->getPid() != pid;
 		);
 		pool->asyncGet(options, callback);
 		EVENTUALLY(5,

From 8cff85c2bd2fba8b2e6afe0409f63c1e5a66caf8 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 14 Oct 2024 13:25:05 -0600
Subject: [PATCH 16/20] =?UTF-8?q?don=E2=80=99t=20select=20a=20totally=20bu?=
 =?UTF-8?q?sy=20process?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../ApplicationPool/Group/ProcessListManagement.cpp  | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 3758d198b0..6be6e7bee3 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -72,11 +72,11 @@ Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
 		Process *process = (*it).get();
 		if (process->getStickySessionId() == id) {
 			return process;
-		} else if (bestProcess == nullptr ||
+		} else if (!process->isTotallyBusy() && (bestProcess == nullptr ||
 				   process->generation > bestProcess->generation ||
 				   (process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
 				   (process->generation == bestProcess->generation && process->spawnStartTime == bestProcess->spawnStartTime && process->busyness() < bestProcess->busyness())
-		) {
+		)) {
 			bestProcess = process;
 		}
 	}
@@ -95,11 +95,11 @@ Group::findBestProcess(const ProcessList &processes) const {
 	for (it = processes.begin(); it != end; it++) {
 		Process *process = (*it).get();
 
-		if (bestProcess == nullptr ||
+		if (!process->isTotallyBusy() && (bestProcess == nullptr ||
 			process->generation > bestProcess->generation ||
 			(process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
 			(process->generation == bestProcess->generation && process->spawnStartTime == bestProcess->spawnStartTime && process->busyness() < bestProcess->busyness())
-		) {
+		)) {
 			bestProcess = process;
 		}
 	}
@@ -127,11 +127,11 @@ Group::findBestEnabledProcess() const {
 		unsigned int gen = process->generation;
 		unsigned long long startTime = process->spawnStartTime;
 		int busyness = enabledProcessBusynessLevels[i];
-		if (bestProcess == nullptr ||
+		if (!process->isTotallyBusy() && (bestProcess == nullptr ||
  			gen > bestProcess->generation ||
 			(gen == bestProcessGen && startTime <  bestProcessStartTime) ||
 			(gen == bestProcessGen && startTime == bestProcessStartTime && busyness < bestProcessBusyness)
-		) {
+		)) {
 			bestProcess = process;
 			bestProcessGen = gen;
 			bestProcessBusyness = busyness;

From b40c7d2d17292baa879a9a6be4213ad45f432a1c Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 14 Oct 2024 13:59:47 -0600
Subject: [PATCH 17/20] fallback to best possible process in case all are
 totally busy

---
 .../Group/ProcessListManagement.cpp           | 49 ++++++++++++++++++-
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
index 6be6e7bee3..c92c587205 100644
--- a/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
+++ b/src/agent/Core/ApplicationPool/Group/ProcessListManagement.cpp
@@ -66,12 +66,21 @@ Group::findProcessWithStickySessionId(unsigned int id) const {
 Process *
 Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
 	Process *bestProcess = nullptr;
+	Process *fallbackProcess = nullptr;
 	ProcessList::const_iterator it;
 	ProcessList::const_iterator end = enabledProcesses.end();
 	for (it = enabledProcesses.begin(); it != end; it++) {
 		Process *process = (*it).get();
 		if (process->getStickySessionId() == id) {
 			return process;
+		} else if (process->isTotallyBusy() && bestProcess == nullptr) {
+			if (fallbackProcess == nullptr ||
+				process->generation > fallbackProcess->generation ||
+				(process->generation == fallbackProcess->generation && process->spawnStartTime < fallbackProcess->spawnStartTime) ||
+				(process->generation == fallbackProcess->generation && process->spawnStartTime == fallbackProcess->spawnStartTime && process->busyness() < fallbackProcess->busyness())
+			) {
+				fallbackProcess = process;
+			}
 		} else if (!process->isTotallyBusy() && (bestProcess == nullptr ||
 				   process->generation > bestProcess->generation ||
 				   (process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
@@ -80,6 +89,9 @@ Group::findBestProcessPreferringStickySessionId(unsigned int id) const {
 			bestProcess = process;
 		}
 	}
+	if (bestProcess == nullptr) {
+		return fallbackProcess;
+	}
 	return bestProcess;
 }
 
@@ -90,12 +102,21 @@ Group::findBestProcess(const ProcessList &processes) const {
 	}
 
 	Process *bestProcess = nullptr;
+	Process *fallbackProcess = nullptr;
 	ProcessList::const_iterator it;
 	ProcessList::const_iterator end = processes.end();
 	for (it = processes.begin(); it != end; it++) {
 		Process *process = (*it).get();
 
-		if (!process->isTotallyBusy() && (bestProcess == nullptr ||
+	 if (process->isTotallyBusy() && bestProcess == nullptr) {
+			if (fallbackProcess == nullptr ||
+				process->generation > fallbackProcess->generation ||
+				(process->generation == fallbackProcess->generation && process->spawnStartTime < fallbackProcess->spawnStartTime) ||
+				(process->generation == fallbackProcess->generation && process->spawnStartTime == fallbackProcess->spawnStartTime && process->busyness() < fallbackProcess->busyness())
+			) {
+				fallbackProcess = process;
+			}
+	 } else if (!process->isTotallyBusy() && (bestProcess == nullptr ||
 			process->generation > bestProcess->generation ||
 			(process->generation == bestProcess->generation && process->spawnStartTime < bestProcess->spawnStartTime) ||
 			(process->generation == bestProcess->generation && process->spawnStartTime == bestProcess->spawnStartTime && process->busyness() < bestProcess->busyness())
@@ -103,6 +124,9 @@ Group::findBestProcess(const ProcessList &processes) const {
 			bestProcess = process;
 		}
 	}
+	if (bestProcess == nullptr) {
+		return fallbackProcess;
+	}
 	return bestProcess;
 }
 
@@ -119,6 +143,12 @@ Group::findBestEnabledProcess() const {
 	unsigned long long bestProcessStartTime = 0;
 	unsigned int bestProcessGen = 0;
 	int bestProcessBusyness = 0;
+
+	Process* fallbackProcess = nullptr;
+	unsigned long long fallbackProcessStartTime = 0;
+	unsigned int fallbackProcessGen = 0;
+	int fallbackProcessBusyness = 0;
+
 	unsigned int size = enabledProcessBusynessLevels.size();
 	const int *enabledProcessBusynessLevels = &this->enabledProcessBusynessLevels[0];
 
@@ -127,7 +157,19 @@ Group::findBestEnabledProcess() const {
 		unsigned int gen = process->generation;
 		unsigned long long startTime = process->spawnStartTime;
 		int busyness = enabledProcessBusynessLevels[i];
-		if (!process->isTotallyBusy() && (bestProcess == nullptr ||
+		bool totallyBusy = process->isTotallyBusy();
+		if (totallyBusy && bestProcess == nullptr) {
+			if (fallbackProcess == nullptr ||
+ 				gen > fallbackProcess->generation ||
+				(gen == fallbackProcessGen && startTime <  fallbackProcessStartTime) ||
+				(gen == fallbackProcessGen && startTime == fallbackProcessStartTime && busyness < fallbackProcessBusyness)
+			) {
+				fallbackProcess = process;
+				fallbackProcessGen = gen;
+				fallbackProcessBusyness = busyness;
+				fallbackProcessStartTime = startTime;
+			}
+		} else if (!totallyBusy && (bestProcess == nullptr ||
  			gen > bestProcess->generation ||
 			(gen == bestProcessGen && startTime <  bestProcessStartTime) ||
 			(gen == bestProcessGen && startTime == bestProcessStartTime && busyness < bestProcessBusyness)
@@ -138,6 +180,9 @@ Group::findBestEnabledProcess() const {
 			bestProcessStartTime = startTime;
 		}
 	}
+	if (bestProcess == nullptr) {
+		return fallbackProcess;
+	}
 	return bestProcess;
 }
 

From dec5f73dd6c31d32159a95ea5a39210f1d59d395 Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Thu, 17 Oct 2024 13:10:50 -0600
Subject: [PATCH 18/20] fix pool test for process generation incrementing

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index bdda8bc6b6..32c732f116 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -652,7 +652,7 @@ namespace tut {
 		EVENTUALLY(5,
 				   LockGuard l(pool->syncher);
 				   vector<ProcessPtr> processes = pool->getProcesses(false);
-				   processes.size() > 0 && processes[0]->getPid() != pid;
+				   result = (processes.size() > 0 && processes[0]->getPid() != pid);
 		);
 		pool->asyncGet(options, callback);
 		EVENTUALLY(5,

From 6de82a7e59cd9da889631275534723429ffa487f Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Fri, 18 Oct 2024 10:59:31 -0600
Subject: [PATCH 19/20] try to make test 8 match new expectations of process
 selection

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 27 ++++++++++++++--------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index 32c732f116..5b7022a1bc 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -434,6 +434,7 @@ namespace tut {
 		EVENTUALLY(5,
 			result = pool->getProcessCount() == 2;
 		);
+	    ProcessPtr first_spawned_process = pool->getProcesses(false)[0];
 
 		// asyncGet() selects some process.
 		pool->asyncGet(options, callback);
@@ -442,31 +443,39 @@ namespace tut {
 		ProcessPtr process1 = currentSession->getProcess()->shared_from_this();
 		currentSession.reset();
 
-		// The first process now has 1 session, so next asyncGet() should
-		// select the other process.
+		// Next asyncGet() should select the process with the lowest spawnTime.
 		pool->asyncGet(options, callback);
 		ensure_equals("(2)", number, 2);
 		SessionPtr session2 = currentSession;
 		ProcessPtr process2 = currentSession->getProcess()->shared_from_this();
 		currentSession.reset();
-		ensure("(3)", process1 != process2);
+		ensure_equals("(3)", process2, first_spawned_process);
 
-		// Both processes now have an equal number of sessions. Next asyncGet()
-		// can select either.
+        // Now that one process is totally busy, next asyncGet() should
+        // select the process that is not totally busy.
 		pool->asyncGet(options, callback);
 		ensure_equals("(4)", number, 3);
 		SessionPtr session3 = currentSession;
 		ProcessPtr process3 = currentSession->getProcess()->shared_from_this();
 		currentSession.reset();
+	    ensure("(5)", process3 != first_spawned_process);
 
-		// One process now has the lowest number of sessions. Next
-		// asyncGet() should select that one.
+		// Next asyncGet() should select the process that is not totally busy again.
 		pool->asyncGet(options, callback);
-		ensure_equals("(5)", number, 4);
+		ensure_equals("(6)", number, 4);
 		SessionPtr session4 = currentSession;
 		ProcessPtr process4 = currentSession->getProcess()->shared_from_this();
 		currentSession.reset();
-		ensure("(6)", process3 != process4);
+		ensure_equals("(7)", process3, process4);
+
+        // Now that both processes are totally busy, next asyncGet()
+        // should select the process that has the lowest spawnTime.
+		pool->asyncGet(options, callback);
+		ensure_equals("(8)", number, 5);
+		SessionPtr session5 = currentSession;
+		ProcessPtr process5 = currentSession->getProcess()->shared_from_this();
+		currentSession.reset();
+		ensure_equals("(9)", process5, first_spawned_process);
 	}
 
 	TEST_METHOD(9) {

From 3b0605ab2aa5807947ab68fe646092f7407076ff Mon Sep 17 00:00:00 2001
From: Camden Narzt <c.narzt@me.com>
Date: Mon, 21 Oct 2024 06:53:50 -0600
Subject: [PATCH 20/20] =?UTF-8?q?test=20doesn=E2=80=99t=20process=20reques?=
 =?UTF-8?q?ts=20on=20totallybusy=20processes=20obviously?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 test/cxx/Core/ApplicationPool/PoolTest.cpp | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/test/cxx/Core/ApplicationPool/PoolTest.cpp b/test/cxx/Core/ApplicationPool/PoolTest.cpp
index 5b7022a1bc..459c60379f 100644
--- a/test/cxx/Core/ApplicationPool/PoolTest.cpp
+++ b/test/cxx/Core/ApplicationPool/PoolTest.cpp
@@ -467,15 +467,6 @@ namespace tut {
 		ProcessPtr process4 = currentSession->getProcess()->shared_from_this();
 		currentSession.reset();
 		ensure_equals("(7)", process3, process4);
-
-        // Now that both processes are totally busy, next asyncGet()
-        // should select the process that has the lowest spawnTime.
-		pool->asyncGet(options, callback);
-		ensure_equals("(8)", number, 5);
-		SessionPtr session5 = currentSession;
-		ProcessPtr process5 = currentSession->getProcess()->shared_from_this();
-		currentSession.reset();
-		ensure_equals("(9)", process5, first_spawned_process);
 	}
 
 	TEST_METHOD(9) {