MDEV-7145: Delayed replication

Merge feature into 10.2 from feature branch.

Delayed replication adds an option

  CHANGE MASTER TO master_delay=<seconds>

Replication will then delay applying events with that many
seconds. This creates a replication slave that reflects the state of
the master some time in the past.

Feature is ported from MySQL source tree.

Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/sql/log.cc b/sql/log.cc
index 569942ac485..2c290715741 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -4304,6 +4304,10 @@ void MYSQL_BIN_LOG::wait_for_last_checkpoint_event()
   relay log.
 
   IMPLEMENTATION
+
+  - You must hold rli->data_lock before calling this function, since
+    it writes group_relay_log_pos and similar fields of
+    Relay_log_info.
   - Protects index file with LOCK_index
   - Delete relevant relay log files
   - Copy all file names after these ones to the front of the index file
@@ -4317,7 +4321,7 @@ void MYSQL_BIN_LOG::wait_for_last_checkpoint_event()
                       read by the SQL slave thread are deleted).
 
   @note
-    - This is only called from the slave-execute thread when it has read
+    - This is only called from the slave SQL thread when it has read
     all commands from a relay log and want to switch to a new relay log.
     - When this happens, we can be in an active transaction as
     a transaction can span over two relay logs
@@ -4348,6 +4352,8 @@ int MYSQL_BIN_LOG::purge_first_log(Relay_log_info* rli, bool included)
   DBUG_ASSERT(rli->slave_running == MYSQL_SLAVE_RUN_NOT_CONNECT);
   DBUG_ASSERT(!strcmp(rli->linfo.log_file_name,rli->event_relay_log_name));
 
+  mysql_mutex_assert_owner(&rli->data_lock);
+
   mysql_mutex_lock(&LOCK_index);
 
   ir= rli->inuse_relaylog_list;
@@ -4406,7 +4412,7 @@ int MYSQL_BIN_LOG::purge_first_log(Relay_log_info* rli, bool included)
   }
 
   /* Store where we are in the new file for the execution thread */
-  flush_relay_log_info(rli);
+  rli->flush();
 
   DBUG_EXECUTE_IF("crash_before_purge_logs", DBUG_SUICIDE(););