From 446c9ec0c814a6bc0a61cfa6d7d9fda0fee67cd3 Mon Sep 17 00:00:00 2001
From: Rahim Kanji <rahim.kanji@outlook.com>
Date: Tue, 14 Mar 2023 13:22:46 +0500
Subject: [PATCH] Added logging

---
 include/MySQL_HostGroups_Manager.h | 23 +++++++++++++++++++++++
 lib/MySQL_HostGroups_Manager.cpp   | 17 +++++++++++++++--
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/include/MySQL_HostGroups_Manager.h b/include/MySQL_HostGroups_Manager.h
index f7cac8cc5..6f29b633c 100644
--- a/include/MySQL_HostGroups_Manager.h
+++ b/include/MySQL_HostGroups_Manager.h
@@ -424,8 +424,31 @@ class MySQL_HostGroups_Manager {
 		~HostGroup_Server_Mapping() = default;
 
 		// Note: copy_if_not_exists, remove, clear method also makes changes to MyHostGroups
+
+		/**
+		  * @brief Copies all unique nodes from source vector to destination vector.
+		  * @details Copies all unique nodes from source vector to destination vector. The source and destination vectors are identified by an input enumeration type, 
+		  *			 which can be either a reader or a writer. During the copying process, the function also adds servers to the HostGroup connection container.
+		  * @param dest_type Input  Can be reader or writer
+		  * @param src_type Input  Can be reader or writer
+		*/
 		void copy_if_not_exists(Type dest_type, Type src_type);
+
+		/**
+		  * @brief Removes node located at the specified index.
+		  * @details Node is removed from vector located at the specified index identified by an input enumeration type. 
+					 Node that was removed is marked as offline in the HostGroup connection container.
+		  * @param dest_type Input  Can be reader or writer
+		  * @param index Input  Index of node to be removed
+		*/
 		void remove(Type type, size_t index);
+
+		/**
+		  * @brief Removes all nodes.
+		  * @details All nodes are removed from vector, identified by an input enumeration type.
+					 Nodes that are removed is marked as offline in the HostGroup connection container.
+		  * @param type Input  Can be reader or writer
+		*/
 		void clear(Type type);
 		//
 
diff --git a/lib/MySQL_HostGroups_Manager.cpp b/lib/MySQL_HostGroups_Manager.cpp
index 8ec0db1f3..06803a923 100644
--- a/lib/MySQL_HostGroups_Manager.cpp
+++ b/lib/MySQL_HostGroups_Manager.cpp
@@ -1966,8 +1966,9 @@ bool MySQL_HostGroups_Manager::commit(
 	if (hgsm_mysql_servers_checksum != table_resultset_checksum[HGM_TABLES::MYSQL_SERVERS] ||
 		hgsm_mysql_replication_hostgroups_checksum != table_resultset_checksum[HGM_TABLES::MYSQL_REPLICATION_HOSTGROUPS])
 	{
-		proxy_info("Checksum for table 'mysql_servers': old:0x%lX new:0x%lX\n", hgsm_mysql_servers_checksum, table_resultset_checksum[HGM_TABLES::MYSQL_SERVERS]);
-		proxy_info("Checksum for table 'mysql_replication_hostgroups': old:0x%lX new:0x%lX\n", hgsm_mysql_replication_hostgroups_checksum, table_resultset_checksum[HGM_TABLES::MYSQL_REPLICATION_HOSTGROUPS]);
+		proxy_info("Rebuilding 'Hostgroup_Manager_Mapping' due to checksums change - mysql_servers { old: 0x%lX, new: 0x%lX }, mysql_replication_hostgroups { old:0x%lX, new:0x%lX }\n", 
+			hgsm_mysql_servers_checksum, table_resultset_checksum[HGM_TABLES::MYSQL_SERVERS], 
+			hgsm_mysql_replication_hostgroups_checksum, table_resultset_checksum[HGM_TABLES::MYSQL_REPLICATION_HOSTGROUPS]);
 		
 		char* error = NULL;
 		int cols = 0;
@@ -4617,6 +4618,8 @@ void MySQL_HostGroups_Manager::read_only_action_v2(const std::list<std::tuple<st
 			if (is_writer == false) {
 				// the server has read_only=0 (writer), but we can't find any writer, 
 				// so we copy all reader nodes to writer
+				proxy_info("Server '%s:%d' found with 'read_only=0', but not found as writer\n", hostname.c_str(), port);
+				proxy_debug(PROXY_DEBUG_MONITOR, 5, "Server '%s:%d' found with 'read_only=0', but not found as writer\n", hostname.c_str(), port);
 				host_server_mapping->copy_if_not_exists(HostGroup_Server_Mapping::Type::WRITER, HostGroup_Server_Mapping::Type::READER);
 
 				if (mysql_thread___monitor_writer_is_also_reader) {
@@ -4628,9 +4631,13 @@ void MySQL_HostGroups_Manager::read_only_action_v2(const std::list<std::tuple<st
 				}
 
 				update_mysql_servers_table = true;
+				proxy_info("Regenerating table 'mysql_servers' due to actions on server '%s:%d'\n", hostname.c_str(), port);
 			} else {
 				bool act = false;
 
+				proxy_info("Server '%s:%d' found with 'read_only=0', also found as writer\n", hostname.c_str(), port);
+				proxy_debug(PROXY_DEBUG_MONITOR, 5, "Server '%s:%d' found with 'read_only=0', also found as writer\n", hostname.c_str(), port);
+
 				// if the server was RO=0 on the previous check then no action is needed
 				if (host_server_mapping->get_readonly_flag() != 0) {
 					// it is the first time that we detect RO on this server
@@ -4673,17 +4680,21 @@ void MySQL_HostGroups_Manager::read_only_action_v2(const std::list<std::tuple<st
 					}
 
 					update_mysql_servers_table = true;
+					proxy_info("Regenerating table 'mysql_servers' due to actions on server '%s:%d'\n", hostname.c_str(), port);
 				}
 			}
 		} else if (read_only == 1) {
 			if (is_writer) {
 				// the server has read_only=1 (reader), but we find it as writer, so we copy all writer nodes to reader (previous reader nodes will be reused)
+				proxy_info("Server '%s:%d' found with 'read_only=1', but not found as reader\n", hostname.c_str(), port);
+				proxy_debug(PROXY_DEBUG_MONITOR, 5, "Server '%s:%d' found with 'read_only=1', but not found as reader\n", hostname.c_str(), port);
 				host_server_mapping->copy_if_not_exists(HostGroup_Server_Mapping::Type::READER, HostGroup_Server_Mapping::Type::WRITER);
 
 				// clearing all writer nodes
 				host_server_mapping->clear(HostGroup_Server_Mapping::Type::WRITER);
 
 				update_mysql_servers_table = true;
+				proxy_info("Regenerating table 'mysql_servers' due to actions on server '%s:%d'\n", hostname.c_str(), port);
 			}
 		} else {
 			// LCOV_EXCL_START
@@ -7637,6 +7648,8 @@ MySrvC* MySQL_HostGroups_Manager::find_server_in_hg(unsigned int _hid, const std
 
 void MySQL_HostGroups_Manager::HostGroup_Server_Mapping::copy_if_not_exists(Type dest_type, Type src_type) {
 
+	assert(dest_type != src_type);
+
 	const std::vector<Node>& src_nodes = mapping[src_type];
 
 	if (src_nodes.empty()) return;