From a808ad54633fde386ec6cd7e372d35bcb4cba63a Mon Sep 17 00:00:00 2001
From: Zwelf <zwelf@strct.cc>
Date: Fri, 21 Aug 2020 10:37:52 +0200
Subject: [PATCH 1/2] Enhance SQL error reporting

---
 .../server/databases/connection_pool.cpp      | 32 +++++++++++++++----
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/engine/server/databases/connection_pool.cpp b/src/engine/server/databases/connection_pool.cpp
index b48f51181..f7a2b8fb4 100644
--- a/src/engine/server/databases/connection_pool.cpp
+++ b/src/engine/server/databases/connection_pool.cpp
@@ -153,6 +153,7 @@ void CDbConnectionPool::Worker()
 			{
 				if(ExecSqlFunc(m_aapDbConnections[Mode::READ][i].get(), pThreadData.get(), false))
 				{
+					dbg_msg("sql", "%s done on read database %d", pThreadData->m_pName, i);
 					Success = true;
 					break;
 				}
@@ -164,6 +165,7 @@ void CDbConnectionPool::Worker()
 			{
 				if(ExecSqlFunc(m_aapDbConnections[Mode::WRITE][i].get(), pThreadData.get(), false))
 				{
+					dbg_msg("sql", "%s done on write database %d", pThreadData->m_pName, i);
 					Success = true;
 					break;
 				}
@@ -174,6 +176,7 @@ void CDbConnectionPool::Worker()
 				{
 					if(ExecSqlFunc(m_aapDbConnections[Mode::WRITE_BACKUP][i].get(), pThreadData.get(), true))
 					{
+						dbg_msg("sql", "%s done on write backup database %d", pThreadData->m_pName, i);
 						Success = true;
 						break;
 					}
@@ -181,8 +184,8 @@ void CDbConnectionPool::Worker()
 			}
 		} break;
 		}
-		if(Success)
-			dbg_msg("sql", "%s done", pThreadData->m_pName);
+		if(!Success)
+			dbg_msg("sql", "%s failed on all databases", pThreadData->m_pName);
 	}
 }
 
@@ -208,18 +211,35 @@ bool CDbConnectionPool::ExecSqlFunc(IDbConnection *pConnection, CSqlExecData *pD
 #if defined(CONF_SQL)
 	catch (sql::SQLException &e)
 	{
-		dbg_msg("sql", "MySQL Error: %s", e.what());
+		dbg_msg("sql", "%s MySQL Error: %s", pData->m_pName, e.what());
 	}
 #endif
 	catch (std::runtime_error &e)
 	{
-		dbg_msg("sql", "SQLite Error: %s", e.what());
+		dbg_msg("sql", "%s SQLite Error: %s", pData->m_pName, e.what());
 	}
 	catch (...)
 	{
-		dbg_msg("sql", "Unexpected exception caught");
+		dbg_msg("sql", "%s Unexpected exception caught", pData->m_pName);
+	}
+	try
+	{
+		pConnection->Unlock();
+	}
+#if defined(CONF_SQL)
+	catch (sql::SQLException &e)
+	{
+		dbg_msg("sql", "%s MySQL Error during unlock: %s", pData->m_pName, e.what());
+	}
+#endif
+	catch (std::runtime_error &e)
+	{
+		dbg_msg("sql", "%s SQLite Error during unlock: %s", pData->m_pName, e.what());
+	}
+	catch (...)
+	{
+		dbg_msg("sql", "%s Unexpected exception caught during unlock", pData->m_pName);
 	}
-	pConnection->Unlock();
 	pConnection->Disconnect();
 	if(!Success)
 		dbg_msg("sql", "%s failed", pData->m_pName);

From 3a30dfbd8495a1405df6e45f3b94eb3db1859135 Mon Sep 17 00:00:00 2001
From: Zwelf <zwelf@strct.cc>
Date: Fri, 21 Aug 2020 19:46:44 +0200
Subject: [PATCH 2/2] Keep connecting to last reachable MySQL server

---
 src/engine/server/databases/connection_pool.cpp | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/engine/server/databases/connection_pool.cpp b/src/engine/server/databases/connection_pool.cpp
index f7a2b8fb4..538bdb5c2 100644
--- a/src/engine/server/databases/connection_pool.cpp
+++ b/src/engine/server/databases/connection_pool.cpp
@@ -133,6 +133,9 @@ void CDbConnectionPool::Worker(void *pUser)
 
 void CDbConnectionPool::Worker()
 {
+	// remember last working server and try to connect to it first
+	int ReadServer = 0;
+	int WriteServer = 0;
 	while(1)
 	{
 		m_NumElem.wait();
@@ -151,9 +154,11 @@ void CDbConnectionPool::Worker()
 		{
 			for(int i = 0; i < (int)m_aapDbConnections[Mode::READ].size(); i++)
 			{
-				if(ExecSqlFunc(m_aapDbConnections[Mode::READ][i].get(), pThreadData.get(), false))
+				int CurServer = (ReadServer + i) % (int)m_aapDbConnections[Mode::READ].size();
+				if(ExecSqlFunc(m_aapDbConnections[Mode::READ][CurServer].get(), pThreadData.get(), false))
 				{
-					dbg_msg("sql", "%s done on read database %d", pThreadData->m_pName, i);
+					ReadServer = CurServer;
+					dbg_msg("sql", "%s done on read database %d", pThreadData->m_pName, CurServer);
 					Success = true;
 					break;
 				}
@@ -163,9 +168,11 @@ void CDbConnectionPool::Worker()
 		{
 			for(int i = 0; i < (int)m_aapDbConnections[Mode::WRITE].size(); i++)
 			{
+				int CurServer = (WriteServer + i) % (int)m_aapDbConnections[Mode::READ].size();
 				if(ExecSqlFunc(m_aapDbConnections[Mode::WRITE][i].get(), pThreadData.get(), false))
 				{
-					dbg_msg("sql", "%s done on write database %d", pThreadData->m_pName, i);
+					WriteServer = CurServer;
+					dbg_msg("sql", "%s done on write database %d", pThreadData->m_pName, CurServer);
 					Success = true;
 					break;
 				}