Adieu slave_list

slave_list was used to provide data for SHOW SLAVE HOSTS and
Slaves_connected status variable.

Introduced binlog_dump_thread_count which is exposed via Slaves_connected
(replaces slave_list.records).

Store Slave_info on THD and access it by iterating server_threads
(replaces slave_list).

Added:
THD::slave_info
binlog_dump_thread_count
show_slave_hosts_callback()

Removed:
slave_list
SLAVE_LIST_CHUNK
SLAVE_ERRMSG_SIZE
slave_list_key()
slave_info_free()
init_slave_list()
end_slave_list()
all_slave_list_mutexes
init_all_slave_list_mutexes()
key_LOCK_slave_list
LOCK_slave_list

Moved:
SLAVE_INFO -> Slave_info
register_slave() -> THD::register_slave()
unregister_slave() -> THD::unregister_slave()

Also removed redundant end_slave() from close_connections(): it is called
again soon afterwards by clean_up().

Pre-requisite for clean MDEV-18450 solution.

mysql-test/suite/perfschema/r/server_init.result

@@ -68,10 +68,6 @@ where name like "wait/synch/mutex/sql/LOCK_crypt";
 count(name)
 1
 select count(name) from mutex_instances
-where name like "wait/synch/mutex/sql/LOCK_slave_list";
-count(name)
-1
-select count(name) from mutex_instances
 where name like "wait/synch/mutex/sql/LOCK_active_mi";
 count(name)
 1

mysql-test/suite/perfschema/t/server_init.test

@@ -70,9 +70,6 @@ select count(name) from mutex_instances
 select count(name) from mutex_instances
  where name like "wait/synch/mutex/sql/LOCK_crypt";
 
-select count(name) from mutex_instances
- where name like "wait/synch/mutex/sql/LOCK_slave_list";
-
 select count(name) from mutex_instances
  where name like "wait/synch/mutex/sql/LOCK_active_mi";
 

sql/mysqld.cc

@@ -705,7 +705,7 @@ mysql_mutex_t
   LOCK_delayed_insert, LOCK_delayed_status, LOCK_delayed_create,
   LOCK_crypt,
   LOCK_global_system_variables,
-  LOCK_user_conn, LOCK_slave_list,
+  LOCK_user_conn,
   LOCK_connection_count, LOCK_error_messages, LOCK_slave_background;
 mysql_mutex_t LOCK_stats, LOCK_global_user_client_stats,
               LOCK_global_table_stats, LOCK_global_index_stats;
@@ -1722,7 +1722,6 @@ static void close_connections(void)
   if (global_system_variables.log_warnings)
     server_threads.iterate(warn_threads_still_active);
 
-  end_slave();
 #ifdef WITH_WSREP
   if (wsrep_inited == 1)
   {
@@ -1947,9 +1946,6 @@ static void clean_up(bool print_message)
   free_global_index_stats();
   delete_dynamic(&all_options);                 // This should be empty
   free_all_rpl_filters();
-#ifdef HAVE_REPLICATION
-  end_slave_list();
-#endif
   wsrep_thr_deinit();
   my_uuid_end();
   delete type_handler_data;
@@ -4820,9 +4816,6 @@ static int init_server_components()
 #endif
 
   my_uuid_init((ulong) (my_rnd(&sql_rand))*12345,12345);
-#ifdef HAVE_REPLICATION
-  init_slave_list();
-#endif
   wt_init();
 
   /* Setup logs */
@@ -7110,11 +7103,7 @@ static int show_slaves_connected(THD *thd, SHOW_VAR *var, char *buff)
 
   var->type= SHOW_LONGLONG;
   var->value= buff;
-  mysql_mutex_lock(&LOCK_slave_list);
-
-  *((longlong *)buff)= slave_list.records;
-
-  mysql_mutex_unlock(&LOCK_slave_list);
+  *((longlong*) buff)= uint32_t(binlog_dump_thread_count);
   return 0;
 }
 

sql/mysqld.h

@@ -624,7 +624,7 @@ extern mysql_mutex_t
        LOCK_item_func_sleep, LOCK_status,
        LOCK_error_log, LOCK_delayed_insert, LOCK_short_uuid_generator,
        LOCK_delayed_status, LOCK_delayed_create, LOCK_crypt, LOCK_timezone,
-       LOCK_slave_list, LOCK_active_mi, LOCK_manager,
+       LOCK_active_mi, LOCK_manager,
        LOCK_global_system_variables, LOCK_user_conn,
        LOCK_prepared_stmt_count, LOCK_error_messages, LOCK_connection_count,
        LOCK_slave_background;

sql/repl_failsafe.cc

@@ -38,13 +38,21 @@
 #include "log_event.h"
 #include <mysql.h>
 
-#define SLAVE_LIST_CHUNK 128
-#define SLAVE_ERRMSG_SIZE (FN_REFLEN+64)
+
+struct Slave_info
+{
+  uint32 server_id;
+  uint32 master_id;
+  char host[HOSTNAME_LENGTH*SYSTEM_CHARSET_MBMAXLEN+1];
+  char user[USERNAME_LENGTH+1];
+  char password[MAX_PASSWORD_LENGTH*SYSTEM_CHARSET_MBMAXLEN+1];
+  uint16 port;
+};
 
 
+Atomic_counter<uint32_t> binlog_dump_thread_count;
 ulong rpl_status=RPL_NULL;
 mysql_mutex_t LOCK_rpl_status;
-HASH slave_list;
 
 const char *rpl_role_type[] = {"MASTER","SLAVE",NullS};
 TYPELIB rpl_role_typelib = {array_elements(rpl_role_type)-1,"",
@@ -81,53 +89,45 @@ void change_rpl_status(ulong from_status, ulong to_status)
     errmsg= msg;\
     goto err; \
   }\
-  strmake(obj,(char*) p,len); \
+  ::strmake(obj, (char*) p, len); \
   p+= len; \
 }\
 
 
-void unregister_slave(THD* thd, bool only_mine, bool need_mutex)
+void THD::unregister_slave()
 {
-  uint32 thd_server_id= thd->variables.server_id;
-  if (thd_server_id)
+  if (auto old_si= slave_info)
   {
-    if (need_mutex)
-      mysql_mutex_lock(&LOCK_slave_list);
-
-    SLAVE_INFO* old_si;
-    if ((old_si = (SLAVE_INFO*)my_hash_search(&slave_list,
-                                              (uchar*)&thd_server_id, 4)) &&
-	(!only_mine || old_si->thd == thd))
-    my_hash_delete(&slave_list, (uchar*)old_si);
-
-    if (need_mutex)
-      mysql_mutex_unlock(&LOCK_slave_list);
+    mysql_mutex_lock(&LOCK_thd_data);
+    slave_info= 0;
+    mysql_mutex_unlock(&LOCK_thd_data);
+    delete old_si;
+    binlog_dump_thread_count--;
   }
 }
 
 
 /**
-  Register slave in 'slave_list' hash table.
+  Register slave
 
   @return
     0	ok
   @return
     1	Error.   Error message sent to client
 */
 
-int register_slave(THD* thd, uchar* packet, size_t packet_length)
+int THD::register_slave(uchar *packet, size_t packet_length)
 {
-  int res;
-  SLAVE_INFO *si;
+  Slave_info *si;
   uchar *p= packet, *p_end= packet + packet_length;
   const char *errmsg= "Wrong parameters to function register_slave";
 
-  if (check_access(thd, REPL_SLAVE_ACL, any_db, NULL, NULL, 0, 0))
+  if (check_access(this, REPL_SLAVE_ACL, any_db, NULL, NULL, 0, 0))
+    return 1;
+  if (!(si= new Slave_info))
     return 1;
-  if (!(si = (SLAVE_INFO*)my_malloc(sizeof(SLAVE_INFO), MYF(MY_WME))))
-    goto err2;
 
-  thd->variables.server_id= si->server_id= uint4korr(p);
+  variables.server_id= si->server_id= uint4korr(p);
   p+= 4;
   get_object(p,si->host, "Failed to register slave: too long 'report-host'");
   get_object(p,si->user, "Failed to register slave: too long 'report-user'");
@@ -146,77 +146,44 @@ int register_slave(THD* thd, uchar* packet, size_t packet_length)
   p += 4;
   if (!(si->master_id= uint4korr(p)))
     si->master_id= global_system_variables.server_id;
-  si->thd= thd;
 
-  mysql_mutex_lock(&LOCK_slave_list);
-  unregister_slave(thd,0,0);
-  res= my_hash_insert(&slave_list, (uchar*) si);
-  mysql_mutex_unlock(&LOCK_slave_list);
-  return res;
+  binlog_dump_thread_count++;
+  unregister_slave();
+  mysql_mutex_lock(&LOCK_thd_data);
+  slave_info= si;
+  mysql_mutex_unlock(&LOCK_thd_data);
+  return 0;
 
 err:
-  my_free(si);
+  delete si;
   my_message(ER_UNKNOWN_ERROR, errmsg, MYF(0)); /* purecov: inspected */
-err2:
   return 1;
 }
 
-extern "C" uint32
-*slave_list_key(SLAVE_INFO* si, size_t *len,
-		my_bool not_used __attribute__((unused)))
-{
-  *len = 4;
-  return &si->server_id;
-}
-
-extern "C" void slave_info_free(void *s)
-{
-  my_free(s);
-}
-
-#ifdef HAVE_PSI_INTERFACE
-static PSI_mutex_key key_LOCK_slave_list;
-
-static PSI_mutex_info all_slave_list_mutexes[]=
-{
-  { &key_LOCK_slave_list, "LOCK_slave_list", PSI_FLAG_GLOBAL}
-};
-
-static void init_all_slave_list_mutexes(void)
-{
-  const char* category= "sql";
-  int count;
-
-  if (PSI_server == NULL)
-    return;
-
-  count= array_elements(all_slave_list_mutexes);
-  PSI_server->register_mutex(category, all_slave_list_mutexes, count);
-}
-#endif /* HAVE_PSI_INTERFACE */
-
-void init_slave_list()
-{
-#ifdef HAVE_PSI_INTERFACE
-  init_all_slave_list_mutexes();
-#endif
-
-  my_hash_init(&slave_list, system_charset_info, SLAVE_LIST_CHUNK, 0, 0,
-               (my_hash_get_key) slave_list_key,
-               (my_hash_free_key) slave_info_free, 0);
-  mysql_mutex_init(key_LOCK_slave_list, &LOCK_slave_list, MY_MUTEX_INIT_FAST);
-}
 
-void end_slave_list()
+static my_bool show_slave_hosts_callback(THD *thd, Protocol *protocol)
 {
-  /* No protection by a mutex needed as we are only called at shutdown */
-  if (my_hash_inited(&slave_list))
+  my_bool res= FALSE;
+  mysql_mutex_lock(&thd->LOCK_thd_data);
+  if (auto si= thd->slave_info)
   {
-    my_hash_free(&slave_list);
-    mysql_mutex_destroy(&LOCK_slave_list);
+    protocol->prepare_for_resend();
+    protocol->store(si->server_id);
+    protocol->store(si->host, &my_charset_bin);
+    if (opt_show_slave_auth_info)
+    {
+      protocol->store(si->user, &my_charset_bin);
+      protocol->store(si->password, &my_charset_bin);
+    }
+    protocol->store((uint32) si->port);
+    protocol->store(si->master_id);
+    res= protocol->write();
   }
+  mysql_mutex_unlock(&thd->LOCK_thd_data);
+  return res;
 }
 
+
 /**
   Execute a SHOW SLAVE HOSTS statement.
 
@@ -258,28 +225,9 @@ bool show_slave_hosts(THD* thd)
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
     DBUG_RETURN(TRUE);
 
-  mysql_mutex_lock(&LOCK_slave_list);
+  if (server_threads.iterate(show_slave_hosts_callback, protocol))
+    DBUG_RETURN(true);
 
-  for (uint i = 0; i < slave_list.records; ++i)
-  {
-    SLAVE_INFO* si = (SLAVE_INFO*) my_hash_element(&slave_list, i);
-    protocol->prepare_for_resend();
-    protocol->store((uint32) si->server_id);
-    protocol->store(si->host, &my_charset_bin);
-    if (opt_show_slave_auth_info)
-    {
-      protocol->store(si->user, &my_charset_bin);
-      protocol->store(si->password, &my_charset_bin);
-    }
-    protocol->store((uint32) si->port);
-    protocol->store((uint32) si->master_id);
-    if (protocol->write())
-    {
-      mysql_mutex_unlock(&LOCK_slave_list);
-      DBUG_RETURN(TRUE);
-    }
-  }
-  mysql_mutex_unlock(&LOCK_slave_list);
   my_eof(thd);
   DBUG_RETURN(FALSE);
 }

sql/repl_failsafe.h

@@ -22,6 +22,7 @@
 #include <my_sys.h>
 #include "slave.h"
 
+extern Atomic_counter<uint32_t> binlog_dump_thread_count;
 typedef enum {RPL_AUTH_MASTER=0,RPL_IDLE_SLAVE,RPL_ACTIVE_SLAVE,
 	      RPL_LOST_SOLDIER,RPL_TROOP_SOLDIER,
 	      RPL_RECOVERY_CAPTAIN,RPL_NULL /* inactive */,
@@ -36,13 +37,7 @@ extern const char* rpl_role_type[], *rpl_status_type[];
 void change_rpl_status(ulong from_status, ulong to_status);
 int find_recovery_captain(THD* thd, MYSQL* mysql);
 
-extern HASH slave_list;
-
 bool show_slave_hosts(THD* thd);
-void init_slave_list();
-void end_slave_list();
-int register_slave(THD* thd, uchar* packet, size_t packet_length);
-void unregister_slave(THD* thd, bool only_mine, bool need_mutex);
 
 #endif /* HAVE_REPLICATION */
 #endif /* REPL_FAILSAFE_INCLUDED */

sql/sql_class.cc

@@ -642,6 +642,10 @@ THD::THD(my_thread_id id, bool is_wsrep_applier, bool skip_global_sys_var_lock)
    tdc_hash_pins(0),
    xid_hash_pins(0),
    m_tmp_tables_locked(false)
+#ifdef HAVE_REPLICATION
+   ,
+   slave_info(0)
+#endif
 #ifdef WITH_WSREP
    ,
    wsrep_applier(is_wsrep_applier),
@@ -1562,6 +1566,9 @@ void THD::cleanup(void)
   DBUG_ASSERT(!mdl_context.has_locks());
 
   apc_target.destroy();
+#ifdef HAVE_REPLICATION
+  unregister_slave();
+#endif
   cleanup_done=1;
   DBUG_VOID_RETURN;
 }

sql/sql_class.h

@@ -89,6 +89,9 @@ class user_var_entry;
 struct Trans_binlog_info;
 class rpl_io_thread_info;
 class rpl_sql_thread_info;
+#ifdef HAVE_REPLICATION
+struct Slave_info;
+#endif
 
 enum enum_ha_read_modes { RFIRST, RNEXT, RPREV, RLAST, RKEY, RNEXT_SAME };
 enum enum_duplicates { DUP_ERROR, DUP_REPLACE, DUP_UPDATE };
@@ -4809,6 +4812,13 @@ class THD: public THD_count, /* this must be first */
   }
 
 public:
+#ifdef HAVE_REPLICATION
+  Slave_info *slave_info;
+
+  int register_slave(uchar *packet, size_t packet_length);
+  void unregister_slave();
+#endif
+
   inline ulong wsrep_binlog_format() const
   {
     return WSREP_BINLOG_FORMAT(variables.binlog_format);

sql/sql_parse.cc

@@ -1654,7 +1654,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
   case COM_REGISTER_SLAVE:
   {
     status_var_increment(thd->status_var.com_register_slave);
-    if (!register_slave(thd, (uchar*)packet, packet_length))
+    if (!thd->register_slave((uchar*) packet, packet_length))
       my_ok(thd);
     break;
   }
@@ -2094,7 +2094,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       general_log_print(thd, command, "Log: '%s'  Pos: %lu", name, pos);
       if (nlen < FN_REFLEN)
         mysql_binlog_send(thd, thd->strmake(name, nlen), (my_off_t)pos, flags);
-      unregister_slave(thd,1,1);
+      thd->unregister_slave();
       /*  fake COM_QUIT -- if we get here, the thread needs to terminate */
       error = TRUE;
       break;