MDEV-16146: MariaDB slave stops with following errors.

Problem:
========
180511 11:07:58 [ERROR] Slave I/O: Unexpected master's heartbeat data:
heartbeat is not compatible with local info;the event's data: log_file_name
mysql-bin.000009 log_pos 1054262041, Error_code: 1623

Analysis:
=========
In replication setup when master server doesn't have any events to send to
slave server it sends an 'Heartbeat_log_event'. This event carries the
current binary log filename and offset details. The offset values is stored
within 4 bytes of event header. When the size of binary log is higher than
UINT32_MAX the log_pos values will not fit in 4 bytes memory.  It overflows
and hence slave stops with an error.

Fix:
===
Since we cannot extend the common_header of Log_event class, a greater than
4GB value of Log_event::log_pos is made to be transported with a HeartBeat
event's sub-header.  Log_event::log_pos in such case is set to zero to
indicate that the 8 byte sub-header is allocated in the event.

In case of cross version replication following behaviour is expected

OLD - Server without fix
NEW - Server with fix

OLD<->NEW : works bidirectionally as long as the binlog offset is
            (normally) within 4GB.

When log_pos > UINT32_MAX
OLD->NEW  : The 'log_pos' is bound to overflow and NEW slave may report
            an invalid event/incompatible heart beat event error.
NEW->OLD  : Since patched server sets log_pos=0 on overflow, OLD slave will
            report invalid event error.

2 files changed, 61 insertions, 0 deletions

diff --git a/mysql-test/suite/rpl/r/rpl_incompatible_heartbeat.result b/mysql-test/suite/rpl/r/rpl_incompatible_heartbeat.result
new file mode 100644
index 00000000000..51da761c50d
--- /dev/null
+++ b/mysql-test/suite/rpl/r/rpl_incompatible_heartbeat.result
@@ -0,0 +1,17 @@
+include/master-slave.inc
+[connection master]
+connection master;
+SET @saved_dbug = @@GLOBAL.debug_dbug;
+SET @@global.debug_dbug= 'd,simulate_pos_4G';
+connection slave;
+include/stop_slave.inc
+CHANGE MASTER TO MASTER_HEARTBEAT_PERIOD=0.001;
+include/start_slave.inc
+connection master;
+SET @@GLOBAL.debug_dbug = @saved_dbug;
+connection slave;
+connection master;
+CREATE TABLE t (f INT) ENGINE=INNODB;
+INSERT INTO t VALUES (10);
+DROP TABLE t;
+include/rpl_end.inc
diff --git a/mysql-test/suite/rpl/t/rpl_incompatible_heartbeat.test b/mysql-test/suite/rpl/t/rpl_incompatible_heartbeat.test
new file mode 100644
index 00000000000..104debe707f
--- /dev/null
+++ b/mysql-test/suite/rpl/t/rpl_incompatible_heartbeat.test
@@ -0,0 +1,44 @@
+# ==== Purpose ====
+#
+# Test verifies that slave IO thread can process heartbeat events with log_pos
+# values higher than UINT32_MAX.
+#
+# ==== Implementation ====
+#
+# Steps:
+#    0 - Stop slave threads. Configure a small master_heartbeat_period.
+#    1 - Using debug points, simulate a huge binlog offset higher than
+#        UINT32_MAX on master.
+#    2 - Start the slave and observe that slave IO thread is able to process
+#        the offset received through heartbeat event.
+#
+# ==== References ====
+#
+# MDEV-16146: MariaDB slave stops with incompatible heartbeat
+#
+--source include/have_debug.inc
+--source include/have_innodb.inc
+--source include/have_binlog_format_mixed.inc
+# Test simulates binarylog offsets higher than UINT32_MAX
+--source include/have_64bit.inc
+--source include/master-slave.inc
+
+--connection master
+SET @saved_dbug = @@GLOBAL.debug_dbug;
+SET @@global.debug_dbug= 'd,simulate_pos_4G';
+
+--connection slave
+--source include/stop_slave.inc
+CHANGE MASTER TO MASTER_HEARTBEAT_PERIOD=0.001;
+--source include/start_slave.inc
+
+--connection master
+sleep 1;
+SET @@GLOBAL.debug_dbug = @saved_dbug;
+--sync_slave_with_master
+
+--connection master
+CREATE TABLE t (f INT) ENGINE=INNODB;
+INSERT INTO t VALUES (10);
+DROP TABLE t;
+--source include/rpl_end.inc