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.

1 files changed, 1 insertions, 122 deletions

diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index 8d1175cba85..86c2ddf8464 100644
--- a/storage/innobase/log/log0log.cc
+++ b/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 @@ wait_suspend_loop:
 		}
 	}
 
-	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 @@ wait_suspend_loop:
 		}
 	}
 
-	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 +