Cleanup of slave code:

- Added testing if connection is killed to shortcut reading of connection data
  This will allow us later in 10.2 to do a cleaner shutdown of slaves (less errors in the log)
- Add new status variables: Slaves_connected, Slaves_running and Slave_connections.
- Use MYSQL_SLAVE_NOT_RUN instead of 0 with slave_running.
- Don't print obvious extra warnings to the error log when slave is shut down normally.

sql/mysqld.cc

@@ -7299,6 +7299,38 @@ static int show_slave_running(THD *thd, SHOW_VAR *var, char *buff)
 }
 
 
+/* How many slaves are connected to this master */
+
+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);
+  return 0;
+}
+
+
+/* How many masters this slave is connected to */
+
+
+static int show_slaves_running(THD *thd, SHOW_VAR *var, char *buff)
+{
+  var->type= SHOW_LONGLONG;
+  var->value= buff;
+  mysql_mutex_lock(&LOCK_active_mi);
+
+  *((longlong *)buff)= master_info_index->any_slave_sql_running();
+
+  mysql_mutex_unlock(&LOCK_active_mi);
+  return 0;
+}
+
+
 static int show_slave_received_heartbeats(THD *thd, SHOW_VAR *var, char *buff)
 {
   Master_info *mi= NULL;
@@ -7950,6 +7982,9 @@ SHOW_VAR status_vars[]= {
   {"Select_scan",	       (char*) offsetof(STATUS_VAR, select_scan_count_), SHOW_LONG_STATUS},
   {"Slave_open_temp_tables",   (char*) &slave_open_temp_tables, SHOW_INT},
 #ifdef HAVE_REPLICATION
+  {"Slaves_connected",        (char*) &show_slaves_connected, SHOW_SIMPLE_FUNC },
+  {"Slaves_running",          (char*) &show_slaves_running, SHOW_SIMPLE_FUNC },
+  {"Slave_connections",       (char*) offsetof(STATUS_VAR, com_register_slave), SHOW_LONG_STATUS},
   {"Slave_heartbeat_period",   (char*) &show_heartbeat_period, SHOW_SIMPLE_FUNC},
   {"Slave_received_heartbeats",(char*) &show_slave_received_heartbeats, SHOW_SIMPLE_FUNC},
   {"Slave_retried_transactions",(char*)&slave_retried_transactions, SHOW_LONG},

sql/net_serv.cc

@@ -34,6 +34,7 @@
   HFTODO this must be hidden if we don't want client capabilities in 
   embedded library
  */
+
 #include <my_global.h>
 #include <mysql.h>
 #include <mysql_com.h>
@@ -107,13 +108,12 @@ extern void query_cache_insert(const char *packet, ulong length,
                                unsigned pkt_nr);
 #endif // HAVE_QUERY_CACHE
 #define update_statistics(A) A
-#else
-#define update_statistics(A)
-#endif
-
-#ifdef MYSQL_SERVER
+extern my_bool thd_net_is_killed();
 /* Additional instrumentation hooks for the server */
 #include "mysql_com_server.h"
+#else
+#define update_statistics(A)
+#define thd_net_is_killed() 0
 #endif
 
 #define TEST_BLOCKING		8
@@ -875,6 +875,16 @@ my_real_read(NET *net, size_t *complen,
 
 	  DBUG_PRINT("info",("vio_read returned %ld  errno: %d",
 			     (long) length, vio_errno(net->vio)));
+
+          if (i== 0 && thd_net_is_killed())
+          {
+            len= packet_error;
+            net->error= 0;
+            net->last_errno= ER_CONNECTION_KILLED;
+            MYSQL_SERVER_my_error(net->last_errno, MYF(0));
+            goto end;
+          }
+
 #if !defined(__WIN__) && defined(MYSQL_SERVER)
 	  /*
 	    We got an error that there was no data on the socket. We now set up

sql/rpl_mi.cc

@@ -35,7 +35,8 @@ Master_info::Master_info(LEX_STRING *connection_name_arg,
    rli(is_slave_recovery), port(MYSQL_PORT),
    checksum_alg_before_fd(BINLOG_CHECKSUM_ALG_UNDEF),
    connect_retry(DEFAULT_CONNECT_RETRY), inited(0), abort_slave(0),
-   slave_running(0), slave_run_id(0), clock_diff_with_master(0),
+   slave_running(MYSQL_SLAVE_NOT_RUN), slave_run_id(0),
+   clock_diff_with_master(0),
    sync_counter(0), heartbeat_period(0), received_heartbeats(0),
    master_id(0), prev_master_id(0),
    using_gtid(USE_GTID_NO), events_queued_since_last_gtid(0),
@@ -1273,23 +1274,24 @@ bool Master_info_index::give_error_if_slave_running()
    The LOCK_active_mi must be held while calling this function.
 
    @return
-   TRUE  	If some slave SQL thread is running.
-   FALSE	No slave SQL thread is running
+   0            No Slave SQL thread is running
+   #		Number of slave SQL thread running
 */
 
-bool Master_info_index::any_slave_sql_running()
+uint Master_info_index::any_slave_sql_running()
 {
+  uint count= 0;
   DBUG_ENTER("any_slave_sql_running");
   if (!this) // master_info_index is set to NULL on server shutdown
-    DBUG_RETURN(TRUE);
+    DBUG_RETURN(count);
 
   for (uint i= 0; i< master_info_hash.records; ++i)
   {
     Master_info *mi= (Master_info *)my_hash_element(&master_info_hash, i);
     if (mi->rli.slave_running != MYSQL_SLAVE_NOT_RUN)
-      DBUG_RETURN(TRUE);
+      count++;
   }
-  DBUG_RETURN(FALSE);
+  DBUG_RETURN(count);
 }
 
 

sql/rpl_mi.h

@@ -218,7 +218,7 @@ class Master_info_index
   Master_info *get_master_info(LEX_STRING *connection_name,
                                Sql_condition::enum_warning_level warning);
   bool give_error_if_slave_running();
-  bool any_slave_sql_running();
+  uint any_slave_sql_running();
   bool start_all_slaves(THD *thd);
   bool stop_all_slaves(THD *thd);
 };

sql/rpl_rli.cc

@@ -63,7 +63,7 @@ Relay_log_info::Relay_log_info(bool is_slave_recovery)
    last_master_timestamp(0), sql_thread_caught_up(true), slave_skip_counter(0),
    abort_pos_wait(0), slave_run_id(0), sql_driver_thd(),
    gtid_skip_flag(GTID_SKIP_NOT), inited(0), abort_slave(0), stop_for_until(0),
-   slave_running(0), until_condition(UNTIL_NONE),
+   slave_running(MYSQL_SLAVE_NOT_RUN), until_condition(UNTIL_NONE),
    until_log_pos(0), retried_trans(0), executed_entries(0),
    m_flags(0)
 {

sql/slave.cc

@@ -112,7 +112,7 @@ static const char *reconnect_messages[SLAVE_RECON_ACT_MAX][SLAVE_RECON_MSG_MAX]=
 {
   {
     "Waiting to reconnect after a failed registration on master",
-    "Slave I/O thread killed while waitnig to reconnect after a failed \
+    "Slave I/O thread killed while waiting to reconnect after a failed \
 registration on master",
     "Reconnecting after a failed registration on master",
     "failed registering on master, reconnecting to try again, \
@@ -4040,10 +4040,9 @@ pthread_handler_t handle_slave_io(void *arg)
     if (request_dump(thd, mysql, mi, &suppress_warnings))
     {
       sql_print_error("Failed on request_dump()");
-      if (check_io_slave_killed(mi, "Slave I/O thread killed while \
-requesting master dump") ||
-          try_to_reconnect(thd, mysql, mi, &retry_count, suppress_warnings,
-                           reconnect_messages[SLAVE_RECON_ACT_DUMP]))
+      if (check_io_slave_killed(mi, NullS) ||
+        try_to_reconnect(thd, mysql, mi, &retry_count, suppress_warnings,
+                         reconnect_messages[SLAVE_RECON_ACT_DUMP]))
         goto err;
       goto connected;
     }
@@ -4059,6 +4058,7 @@ requesting master dump") ||
       });
     const char *event_buf;
 
+    mi->slave_running= MYSQL_SLAVE_RUN_READING;
     DBUG_ASSERT(mi->last_error().number == 0);
     while (!io_slave_killed(mi))
     {
@@ -4071,8 +4071,7 @@ requesting master dump") ||
       */
       THD_STAGE_INFO(thd, stage_waiting_for_master_to_send_event);
       event_len= read_event(mysql, mi, &suppress_warnings);
-      if (check_io_slave_killed(mi, "Slave I/O thread killed while \
-reading event"))
+      if (check_io_slave_killed(mi, NullS))
         goto err;
       DBUG_EXECUTE_IF("FORCE_SLAVE_TO_RECONNECT_EVENT",
         if (!retry_count_event)

sql/sql_class.cc

@@ -1743,7 +1743,8 @@ void add_diff_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var,
 void THD::awake(killed_state state_to_set)
 {
   DBUG_ENTER("THD::awake");
-  DBUG_PRINT("enter", ("this: %p current_thd: %p", this, current_thd));
+  DBUG_PRINT("enter", ("this: %p current_thd: %p  state: %d",
+                       this, current_thd, (int) state_to_set));
   THD_CHECK_SENTRY(this);
   mysql_mutex_assert_owner(&LOCK_thd_data);
 
@@ -3799,6 +3800,12 @@ void thd_increment_bytes_sent(ulong length)
   }
 }
 
+my_bool thd_net_is_killed()
+{
+  THD *thd= current_thd;
+  return thd && thd->killed ? 1 : 0;
+}
+
 
 void thd_increment_bytes_received(ulong length)
 {

sql/sql_class.h

@@ -656,6 +656,7 @@ typedef struct system_status_var
 {
   ulong com_other;
   ulong com_stat[(uint) SQLCOM_END];
+  ulong com_register_slave;
   ulong created_tmp_disk_tables_;
   ulong created_tmp_tables_;
   ulong ha_commit_count;

sql/sql_parse.cc

@@ -1177,6 +1177,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 #ifdef HAVE_REPLICATION
   case COM_REGISTER_SLAVE:
   {
+    status_var_increment(thd->status_var.com_register_slave);
     if (!register_slave(thd, (uchar*)packet, packet_length))
       my_ok(thd);
     break;