MDEV-34504 PURGE BINARY LOGS not working anymore

PURGE BINARY LOGS did not always purge binary logs. This commit fixes
some of the issues and adds notifications if a binary log cannot be
purged.

User visible changes:
- 'PURGE BINARY LOG TO log_name' and 'PURGE BINARY LOGS BEFORE date'
  worked differently. 'TO' ignored 'slave_connections_needed_for_purge'
  while 'BEFORE' did not. Now both versions ignores the
  'slave_connections_needed_for_purge variable'.
- 'PURGE BINARY LOG..' commands now returns 'note' if a binary log cannot
   be deleted like
   Note 1375 Binary log 'master-bin.000004' is not purged because it is
             the current active binlog
- Automatic binary log purges, based on date or size, will write a
  note to the error log if a binary log matching the size or date
  cannot yet be deleted.
- If 'slave_connections_needed_for_purge' is set from a config or
  command line, it is set to 0 if Galera is enabled and 1 otherwise
  (old default). This ensures that automatic binary log purge works
  with Galera as before the addition of
  'slave_connections_needed_for_purge'.
  If the variable is changed to 0, a warning will be printed to the error
  log.

Code changes:
- Added THD argument to several purge_logs related functions that needed
  THD.
- Added 'interactive' options to purge_logs functions. This allowed
  me to remove testing of sql_command == SQLCOM_PURGE.
- Changed purge_logs_before_date() to first check if log is applicable
  before calling can_purge_logs(). This ensures we do not get a
  notification for logs that does not match the remove criteria.
- MYSQL_BIN_LOG::can_purge_log() will write notifications to the user
  or error log if a log cannot yet be removed.
- log_in_use() will return reason why a binary log cannot be removed.

Changes to keep code consistent:
- Moved checking of binlog_format for Galera to be after Galera is
  initialized (The old check never worked). If Galera is enabled
  we now change the binlog_format to ROW, with a warning, instead of
  aborting the server. If this change happens a warning will be printed to
  the error log.
- Print a warning if Galera or FLASHBACK changes the binlog_format
  to ROW. Before it was done silently.

Reviewed by: Sergei Golubchik <serg@mariadb.com>,
             Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/suite/rpl/r/purge_binlog.result

@@ -0,0 +1,52 @@
+include/master-slave.inc
+[connection master]
+#
+# MDEV-34504 PURGE BINARY LOGS not working anymore
+#
+select @@slave_connections_needed_for_purge;
+@@slave_connections_needed_for_purge
+0
+set @old_dbug= @@global.debug_dbug;
+create table t1 (a int, b varchar(32768));
+insert into t1 values(1,repeat("a",32768));
+connection slave;
+select a from t1;
+a
+1
+set @@global.debug_dbug= "+d,pause_before_io_read_event";
+connection master;
+insert into t1 values(2,repeat("b",32768));
+insert into t1 values(3,repeat("c",32768));
+connection slave;
+set debug_sync='now wait_for io_thread_at_read_event';
+select a from t1;
+a
+1
+connection master;
+FLUSH BINARY LOGS;
+show binary logs;
+Log_name	File_size
+master-bin.000001	#
+master-bin.000002	#
+PURGE BINARY LOGS TO 'master-bin.000002';
+Warnings:
+Note	1375	Binary log XXX is not purged because it is in use by a slave thread
+show binary logs;
+Log_name	File_size
+master-bin.000001	#
+master-bin.000002	#
+connection slave;
+set @@global.debug_dbug= @old_dbug;
+set debug_sync='now signal io_thread_continue_read_event';
+connection master;
+connection slave;
+select count(*) from t1;
+count(*)
+153
+connection master;
+PURGE BINARY LOGS TO 'master-bin.000002';
+show binary logs;
+Log_name	File_size
+master-bin.000002	#
+drop table t1;
+include/rpl_end.inc

mysql-test/suite/rpl/r/rpl_rotate_logs.result

@@ -70,6 +70,8 @@ master-bin.000002	#
 master-bin.000003	#
 SELECT @time_for_purge:=DATE_ADD('tmpval', INTERVAL 1 SECOND);
 purge master logs before (@time_for_purge);
+Warnings:
+Note	1375	Binary log 'master-bin.000003' is not purged because it is the current active binlog
 show binary logs;
 Log_name	File_size
 master-bin.000003	#

mysql-test/suite/rpl/t/purge_binlog.test

@@ -0,0 +1,51 @@
+--source include/have_debug.inc
+--source include/have_debug_sync.inc
+--source include/master-slave.inc
+--source include/have_binlog_format_row.inc
+
+--echo #
+--echo # MDEV-34504 PURGE BINARY LOGS not working anymore
+--echo #
+
+select @@slave_connections_needed_for_purge;
+set @old_dbug= @@global.debug_dbug;
+
+create table t1 (a int, b varchar(32768));
+insert into t1 values(1,repeat("a",32768));
+--sync_slave_with_master
+select a from t1;
+set @@global.debug_dbug= "+d,pause_before_io_read_event";
+--connection master
+insert into t1 values(2,repeat("b",32768));
+insert into t1 values(3,repeat("c",32768));
+--connection slave
+set debug_sync='now wait_for io_thread_at_read_event';
+select a from t1;
+--connection master
+--disable_query_log
+let $i=150;
+while ($i)
+{
+--eval insert into t1 values($i+4,repeat(char(64+$i),32768));
+--dec $i
+}
+--enable_query_log
+
+FLUSH BINARY LOGS;
+--source include/show_binary_logs.inc
+--let $purge_to_binlog= query_get_value(SHOW MASTER STATUS, File, 1)
+--replace_regex /Binary log.*is not/Binary log XXX is not/
+--eval PURGE BINARY LOGS TO '$purge_to_binlog'
+--source include/show_binary_logs.inc
+--connection slave
+set @@global.debug_dbug= @old_dbug;
+set debug_sync='now signal io_thread_continue_read_event';
+--connection master
+--sync_slave_with_master
+select count(*) from t1;
+--connection master
+--eval PURGE BINARY LOGS TO '$purge_to_binlog'
+--source include/show_binary_logs.inc
+drop table t1;
+
+--source include/rpl_end.inc

mysql-test/suite/rpl/t/rpl_rotate_logs.test

@@ -190,10 +190,12 @@ sync_slave_with_master;
 #
 --error 1220
 show binlog events in 'non existing_binlog_file';
+--disable_warnings
 purge master logs before now();
 --error 1220
 show binlog events in '';
 purge master logs before now();
+--enable_warnings
 
 --echo End of 5.0 tests
 --echo #cleanup