MDEV-21870 Deprecate and ignore innodb_scrub_log and innodb_scrub_log_speed

The configuration parameter innodb_scrub_log never really worked, as
reported in MDEV-13019 and MDEV-18370.

Because MDEV-14425 is changing the redo log format, the innodb_scrub_log
feature would have to be adjusted for it. Due to the known problems,
it is easier to remove the feature for now, and to ignore and deprecate
the parameters.

If old log contents should be kept secret, then enabling innodb_encrypt_log
or setting a smaller innodb_log_file_size could help.

mysql-test/suite/encryption/r/innodb-scrub-log.result

-create table t1(a int not null primary key auto_increment,
-b varchar(200), c char(100), d varchar(150)) engine=innodb;
-DROP TABLE t1;

mysql-test/suite/encryption/t/innodb-scrub-log.opt

---loose-innodb-scrub-log=on

mysql-test/suite/encryption/t/innodb-scrub-log.test

---source include/have_innodb.inc
-
-#
-# MDEV-11705: InnoDB: Failing assertion: (&log_sys.mutex)->is_owned() if server started with innodb-scrub-log
-#
-
-create table t1(a int not null primary key auto_increment,
-b varchar(200), c char(100), d varchar(150)) engine=innodb;
-
-let $wait_condition= SELECT variable_value FROM information_schema.global_status WHERE variable_name = 'innodb_scrub_log';
---source include/wait_condition.inc
-
-DROP TABLE t1;

mysql-test/suite/sys_vars/r/innodb_scrub_log_speed_basic.result

@@ -3,12 +3,16 @@ SELECT @@GLOBAL.innodb_scrub_log_speed;
 256
 200 Expected
 SET @@GLOBAL.innodb_scrub_log_speed=100;
+Warnings:
+Warning	138	The parameter innodb_scrub_log_speed is deprecated and has no effect.
 1 Expected
 SELECT @@GLOBAL.innodb_scrub_log_speed;
 @@GLOBAL.innodb_scrub_log_speed
-100
+256
 100 Expected
 SET @@GLOBAL.innodb_scrub_log_speed=DEFAULT;
+Warnings:
+Warning	138	The parameter innodb_scrub_log_speed is deprecated and has no effect.
 1 Expected
 SELECT @@GLOBAL.innodb_scrub_log_speed;
 @@GLOBAL.innodb_scrub_log_speed

mysql-test/suite/sys_vars/r/sysvars_innodb.result

@@ -1682,7 +1682,7 @@ SESSION_VALUE	NULL
 DEFAULT_VALUE	OFF
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	BOOLEAN
-VARIABLE_COMMENT	Enable background redo log scrubbing
+VARIABLE_COMMENT	Deprecated parameter with no effect.
 NUMERIC_MIN_VALUE	NULL
 NUMERIC_MAX_VALUE	NULL
 NUMERIC_BLOCK_SIZE	NULL
@@ -1694,7 +1694,7 @@ SESSION_VALUE	NULL
 DEFAULT_VALUE	256
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	BIGINT UNSIGNED
-VARIABLE_COMMENT	Background redo log scrubbing speed in bytes/sec
+VARIABLE_COMMENT	Deprecated parameter with no effect.
 NUMERIC_MIN_VALUE	1
 NUMERIC_MAX_VALUE	50000
 NUMERIC_BLOCK_SIZE	0

storage/innobase/handler/ha_innodb.cc

@@ -1094,7 +1094,6 @@ static SHOW_VAR innodb_status_variables[]= {
    &export_vars.innodb_scrub_page_split_failures_missing_index, SHOW_SIZE_T},
   {"scrub_background_page_split_failures_unknown",
    &export_vars.innodb_scrub_page_split_failures_unknown, SHOW_SIZE_T},
-  {"scrub_log", &export_vars.innodb_scrub_log, SHOW_LONGLONG},
   {"encryption_num_key_requests", &export_vars.innodb_encryption_key_requests,
    SHOW_LONGLONG},
 
@@ -3432,7 +3431,16 @@ static const char* innodb_log_compressed_pages_msg
 static my_bool	innodb_log_optimize_ddl;
 static const char* innodb_log_optimize_ddl_msg
 = "The parameter innodb_log_optimize_ddl is deprecated and has no effect.";
-
+/** Deprecated parameter with no effect */
+static my_bool innodb_scrub_log;
+/** Deprecation message for innodb_scrub_log */
+static const char* innodb_scrub_log_msg
+= "The parameter innodb_scrub_log is deprecated and has no effect.";
+/** Deprecated parameter with no effect */
+static ulonglong innodb_scrub_log_speed;
+/** Deprecation message for innodb_scrub_log_speed */
+static const char* innodb_scrub_log_speed_msg
+= "The parameter innodb_scrub_log_speed is deprecated and has no effect.";
 /** Deprecated parameter with no effect */
 static ulong innodb_undo_logs;
 /** Deprecation message for innodb_undo_logs */
@@ -3761,6 +3769,16 @@ static int innodb_init_params()
 		deprecated::innodb_log_optimize_ddl = FALSE;
 	}
 
+	if (UNIV_UNLIKELY(deprecated::innodb_scrub_log)) {
+		sql_print_warning(deprecated::innodb_scrub_log_msg);
+		deprecated::innodb_scrub_log = FALSE;
+	}
+
+	if (UNIV_UNLIKELY(deprecated::innodb_scrub_log_speed != 256)) {
+		sql_print_warning(deprecated::innodb_scrub_log_speed_msg);
+		deprecated::innodb_scrub_log_speed = 256;
+	}
+
 	if (UNIV_UNLIKELY(deprecated::innodb_buffer_pool_instances)) {
 		sql_print_warning("The parameter innodb_buffer_pool_instances"
 				  " is deprecated and has no effect.");
@@ -18906,6 +18924,16 @@ innodb_undo_logs_warn(THD* thd, st_mysql_sys_var*, void*, const void*)
 			    deprecated::innodb_undo_logs_msg);
 }
 
+/** Issue a deprecation warning for SET GLOBAL innodb_scrub_log_speed.
+@param[in,out]	thd	client connection */
+static void
+innodb_scrub_log_speed_warn(THD* thd, st_mysql_sys_var*, void*, const void*)
+{
+	push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
+			    HA_ERR_UNSUPPORTED,
+			    deprecated::innodb_scrub_log_speed_msg);
+}
+
 static SHOW_VAR innodb_status_variables_export[]= {
 	{"Innodb", (char*) &show_innodb_vars, SHOW_FUNC},
 	{NullS, NullS, SHOW_LONG}
@@ -20147,18 +20175,15 @@ static MYSQL_SYSVAR_UINT(encryption_rotation_iops, srv_n_fil_crypt_iops,
 			 innodb_encryption_rotation_iops_update,
 			 srv_n_fil_crypt_iops, 0, UINT_MAX32, 0);
 
-static MYSQL_SYSVAR_BOOL(scrub_log, srv_scrub_log,
+static MYSQL_SYSVAR_BOOL(scrub_log, deprecated::innodb_scrub_log,
   PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
-  "Enable background redo log scrubbing",
+  innodb_deprecated_ignored,
   0, 0, 0);
 
-static MYSQL_SYSVAR_ULONGLONG(scrub_log_speed, innodb_scrub_log_speed,
+static MYSQL_SYSVAR_ULONGLONG(scrub_log_speed, deprecated::innodb_scrub_log_speed,
   PLUGIN_VAR_OPCMDARG,
-  "Background redo log scrubbing speed in bytes/sec",
-  NULL, NULL,
-  256,              /* 256 bytes/sec, corresponds to 2000 ms scrub_log_interval */
-  1,                /* min */
-  50000, 0);        /* 50Kbyte/sec, corresponds to 10 ms scrub_log_interval */
+  innodb_deprecated_ignored, NULL, innodb_scrub_log_speed_warn,
+  256, 1, 50000, 0);
 
 static MYSQL_SYSVAR_BOOL(encrypt_log, srv_encrypt_log,
   PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,

storage/innobase/include/log0log.h

@@ -875,15 +875,6 @@ inline void log_t::file::set_lsn_offset(lsn_t a_lsn) {
 /** Release the log sys mutex. */
 #define log_mutex_exit() mutex_exit(&log_sys.mutex)
 
-
-/* log scrubbing speed, in bytes/sec */
-extern ulonglong innodb_scrub_log_speed;
-
-/** Event to wake up log_scrub_thread */
-extern os_event_t	log_scrub_event;
-/** Whether log_scrub_thread is active */
-extern bool		log_scrub_thread_active;
-
 #include "log0log.ic"
 
 #endif

storage/innobase/include/srv0srv.h

@@ -185,9 +185,6 @@ struct srv_stats_t
 	/** Number of encryption_get_latest_key_version calls */
 	ulint_ctr_64_t		n_key_requests;
 
-	/** Number of log scrub operations */
-	ulint_ctr_64_t		n_log_scrubs;
-
 	/** Number of spaces in keyrotation list */
 	ulint_ctr_64_t		key_rotation_list_length;
 
@@ -483,9 +480,6 @@ extern ibool	srv_print_verbose_log;
 extern bool	srv_monitor_active;
 
 
-/* TRUE if enable log scrubbing */
-extern my_bool	srv_scrub_log;
-
 extern ulong	srv_n_spin_wait_rounds;
 extern ulong	srv_n_free_tickets_to_enter;
 extern ulong	srv_thread_sleep_delay;
@@ -971,7 +965,6 @@ struct export_var_t{
 	ulint innodb_scrub_page_split_failures_out_of_filespace;
 	ulint innodb_scrub_page_split_failures_missing_index;
 	ulint innodb_scrub_page_split_failures_unknown;
-	int64_t innodb_scrub_log;
 };
 
 /** Thread slot in the thread table.  */

storage/innobase/log/log0log.cc

@@ -66,10 +66,6 @@ to the InnoDB redo log. */
 /** Redo log system */
 log_t	log_sys;
 
-/* Next log block number to do dummy record filling if no log records written
-for a while */
-static ulint		next_lbn_to_pad = 0;
-
 /* These control how often we print warnings if the last checkpoint is too
 old */
 static bool	log_has_printed_chkp_warning = false;
@@ -102,15 +98,6 @@ the previous */
 #define LOG_UNLOCK_NONE_FLUSHED_LOCK	1
 #define LOG_UNLOCK_FLUSH_LOCK		2
 
-/** Event to wake up log_scrub_thread */
-os_event_t	log_scrub_event;
-/** Whether log_scrub_thread is active */
-bool		log_scrub_thread_active;
-
-extern "C" UNIV_INTERN
-os_thread_ret_t
-DECLARE_THREAD(log_scrub_thread)(void*);
-
 /****************************************************************//**
 Returns the oldest modified block lsn in the pool, or log_sys.lsn if none
 exists.
@@ -553,12 +540,6 @@ void log_t::create()
 
   buf_free= LOG_BLOCK_HDR_SIZE;
   lsn= LOG_START_LSN + LOG_BLOCK_HDR_SIZE;
-
-  log_scrub_thread_active= !srv_read_only_mode && srv_scrub_log;
-  if (log_scrub_thread_active) {
-    log_scrub_event= os_event_create("log_scrub_event");
-    os_thread_create(log_scrub_thread, NULL, NULL);
-  }
 }
 
 mapped_file_t::~mapped_file_t() noexcept
@@ -1766,18 +1747,13 @@ logs_empty_and_mark_files_at_shutdown(void)
 		}
 	}
 
-	if (log_scrub_thread_active) {
-		ut_ad(!srv_read_only_mode);
-		os_event_set(log_scrub_event);
-	}
-
 	if (log_sys.is_initialised()) {
 		log_mutex_enter();
 		const ulint	n_write	= log_sys.n_pending_checkpoint_writes;
 		const ulint	n_flush	= log_sys.pending_flushes;
 		log_mutex_exit();
 
-		if (log_scrub_thread_active || n_write || n_flush) {
+		if (n_write || n_flush) {
 			if (srv_print_verbose_log && count > 600) {
 				ib::info() << "Pending checkpoint_writes: "
 					<< n_write
@@ -1789,8 +1765,6 @@ logs_empty_and_mark_files_at_shutdown(void)
 		}
 	}
 
-	ut_ad(!log_scrub_thread_active);
-
 	if (!buf_pool) {
 		ut_ad(!srv_was_started);
 	} else if (ulint pending_io = buf_pool_check_no_pending_io()) {
@@ -1989,104 +1963,9 @@ void log_t::close()
   mutex_free(&mutex);
   mutex_free(&log_flush_order_mutex);
 
-  if (!srv_read_only_mode && srv_scrub_log)
-    os_event_destroy(log_scrub_event);
-
   recv_sys.close();
 }
 
-/******************************************************//**
-Pads the current log block full with dummy log records. Used in producing
-consistent archived log file and scrubbing redo log. */
-static
-void
-log_pad_current_log_block(void)
-/*===========================*/
-{
-	byte		b		= 0;
-	ulint		pad_length;
-	ulint		i;
-	lsn_t		lsn;
-
-	ut_ad(!recv_no_log_write);
-	/* We retrieve lsn only because otherwise gcc crashed on HP-UX */
-	lsn = log_reserve_and_open(OS_FILE_LOG_BLOCK_SIZE);
-
-	pad_length = log_sys.trailer_offset()
-		- log_sys.buf_free % OS_FILE_LOG_BLOCK_SIZE;
-	if (pad_length == log_sys.payload_size()) {
-		pad_length = 0;
-	}
-
-	if (pad_length) {
-		srv_stats.n_log_scrubs.inc();
-	}
-
-	for (i = 0; i < pad_length; i++) {
-		log_write_low(&b, 1);
-	}
-
-	lsn = log_sys.lsn;
-
-	log_close();
-
-	ut_a(lsn % OS_FILE_LOG_BLOCK_SIZE == LOG_BLOCK_HDR_SIZE);
-}
-
-/*****************************************************************//*
-If no log record has been written for a while, fill current log
-block with dummy records. */
-static
-void
-log_scrub()
-/*=========*/
-{
-	log_mutex_enter();
-	ulint cur_lbn = log_block_convert_lsn_to_no(log_sys.lsn);
-
-	if (next_lbn_to_pad == cur_lbn)
-	{
-		log_pad_current_log_block();
-	}
-
-	next_lbn_to_pad = log_block_convert_lsn_to_no(log_sys.lsn);
-	log_mutex_exit();
-}
-
-/* log scrubbing speed, in bytes/sec */
-UNIV_INTERN ulonglong innodb_scrub_log_speed;
-
-/*****************************************************************//**
-This is the main thread for log scrub. It waits for an event and
-when waked up fills current log block with dummy records and
-sleeps again.
-@return this function does not return, it calls os_thread_exit() */
-extern "C" UNIV_INTERN
-os_thread_ret_t
-DECLARE_THREAD(log_scrub_thread)(void*)
-{
-	ut_ad(!srv_read_only_mode);
-
-	while (srv_shutdown_state < SRV_SHUTDOWN_FLUSH_PHASE) {
-		/* log scrubbing interval in µs. */
-		ulonglong interval = 1000*1000*512/innodb_scrub_log_speed;
-
-		os_event_wait_time(log_scrub_event, static_cast<ulint>(interval));
-
-		log_scrub();
-
-		os_event_reset(log_scrub_event);
-	}
-
-	log_scrub_thread_active = false;
-
-	/* We count the number of threads in os_thread_exit(). A created
-	thread should always use that to exit and not use return() to exit. */
-	os_thread_exit();
-
-	OS_THREAD_DUMMY_RETURN;
-}
-
 std::string get_log_file_path(const char *filename)
 {
   const size_t size= strlen(srv_log_group_home_dir) + /* path separator */ 1 +

storage/innobase/srv/srv0srv.cc

@@ -84,8 +84,6 @@ UNIV_INTERN ulong	srv_fatal_semaphore_wait_threshold =  DEFAULT_SRV_FATAL_SEMAPH
 in microseconds, in order to reduce the lagging of the purge thread. */
 ulint	srv_dml_needed_delay;
 
-my_bool	srv_scrub_log;
-
 const char*	srv_main_thread_op_info = "";
 
 /** Prefix used by MySQL to indicate pre-5.1 table name encoding */
@@ -1361,7 +1359,6 @@ srv_export_innodb_status(void)
 			scrub_stat.page_split_failures_missing_index;
 		export_vars.innodb_scrub_page_split_failures_unknown =
 			scrub_stat.page_split_failures_unknown;
-		export_vars.innodb_scrub_log = srv_stats.n_log_scrubs;
 	}
 
 	mutex_exit(&srv_innodb_monitor_mutex);

storage/innobase/srv/srv0start.cc

@@ -892,10 +892,6 @@ srv_shutdown_all_bg_threads()
 			if (srv_n_fil_crypt_threads_started) {
 				os_event_set(fil_crypt_threads_event);
 			}
-
-			if (log_scrub_thread_active) {
-				os_event_set(log_scrub_event);
-			}
 		}
 
 		if (srv_start_state_is_set(SRV_START_STATE_IO)) {