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Code Activity

MDEV-40545 mariadb-binlog --force-read loops on truncated events

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What was wrong:
With --force-read, Log_event::read_log_event() returned a synthetic
"Encrypted event" (Unknown_log_event) for every read error. A
truncated event is such an error, so mariadb-binlog printed a fake
event instead of stopping, and on most truncated binlogs it then never
stopped at all.

How it is fixed:
The synthetic event is meant for encrypted events that mariadb-binlog
cannot decrypt (MDEV-11319). It is now returned only for a decryption
failure. Other read errors, like a truncated event or an out of memory
error, are critical: continuing after them cannot produce meaningful
output, so they are reported and mariadb-binlog stops as it does
without --force-read.

How it is tested:
main.mysqlbinlog_force_read_truncated reads two truncated binlogs from
std_data, one with a truncated event header and one with a truncated
event body. The test loops forever without the fix.
This commit is contained in:
Rion Bora
2026-10-12 12:18:38 +05:30
committed by ParadoxV5
parent 79655b07dc
commit fc9fdbcc09
5 changed files with 35 additions and 5 deletions
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18
mysql-test/main/mysqlbinlog_force_read_truncated.result Normal file
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@@ -0,0 +1,18 @@
#
# MDEV-40545: --force-read must not loop on a truncated event
#
# The event header is truncated
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!40019 SET @@session.max_delayed_threads=0*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
ERROR: Error in Log_event::read_log_event(): 'Event truncated'
ERROR: Could not read entry at offset 4: Error in log format or read error.
# The event body is truncated
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!40019 SET @@session.max_delayed_threads=0*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
ERROR: Error in Log_event::read_log_event(): 'Event truncated', data_len: 94, event_type: 15
ERROR: Could not read entry at offset 4: Error in log format or read error.
# End of 11.4 tests

13
mysql-test/main/mysqlbinlog_force_read_truncated.test Normal file
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@@ -0,0 +1,13 @@
--echo #
--echo # MDEV-40545: --force-read must not loop on a truncated event
--echo #
--echo # The event header is truncated
--error 1
--exec $MYSQL_BINLOG --short-form --force-read $MYSQL_TEST_DIR/std_data/truncated_binlog_header.000001 2>&1
--echo # The event body is truncated
--error 1
--exec $MYSQL_BINLOG --short-form --force-read $MYSQL_TEST_DIR/std_data/truncated_binlog_body.000001 2>&1
--echo # End of 11.4 tests

BIN
mysql-test/std_data/truncated_binlog_body.000001 Normal file
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BIN
mysql-test/std_data/truncated_binlog_header.000001 Normal file
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9
sql/log_event.cc
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@@ -935,6 +935,10 @@ Log_event* Log_event::read_log_event(IO_CACHE* file, int *out_error,
error= "Event too big";
goto err;
case LOG_READ_DECRYPT:
#ifdef MYSQL_CLIENT
if (force_opt)
DBUG_RETURN(new Unknown_log_event());
#endif
error= "Event decryption failure";
goto err;
case LOG_READ_CHECKSUM_FAILURE:
@@ -956,11 +960,6 @@ err:
if (unlikely(error))
{
DBUG_ASSERT(!res);
#ifdef MYSQL_CLIENT
if (force_opt)
DBUG_RETURN(new Unknown_log_event());
#endif
/*
The SQL slave thread will check *out_error to know
if there was an I/O error. Even if there is no "low-level" I/O errors