| Bug #61096 | Replication from master with new checksum algorithm | ||
|---|---|---|---|
| Submitted: | 9 May 2011 9:40 | Modified: | 7 Mar 2012 12:02 |
| Reporter: | Mats Kindahl | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Replication | Severity: | S2 (Serious) |
| Version: | 5.6 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | checksum, replication | ||
[9 May 2011 9:57]
MySQL Verification Team
Thank you for the bug report.
[7 Mar 2012 12:02]
Jon Stephens
Fixed in 5.6. Documented as follows in the 5.6.6 changelog:
Setting binlog_checksum on the master to a value that was unknown
on the slave caused replication to fail. Now in such cases, the
checksum is disabled on the slave and replication stops with an
appropriate error message.
Closed.
Description: In the event that the master is extended with a new checksum algorithm not known to the slave, the slave will deduce that there is no checksum support in the master. However, the master will send events with the new checksum while the slave treats it as no checksum, with potential for treating the checksum as part of the event body. How to repeat: See line 1753 in rpl_slave.cc: if (!mysql_real_query(mysql, STRING_WITH_LEN("SELECT @master_binlog_checksum")) && (master_res= mysql_store_result(mysql)) && (master_row= mysql_fetch_row(master_res)) && (master_row[0] != NULL)) { mi->checksum_alg_before_fd= (uint8) find_type(master_row[0], &binlog_checksum_typelib, 1) - 1; // valid outcome is either of DBUG_ASSERT(mi->checksum_alg_before_fd == BINLOG_CHECKSUM_ALG_OFF || mi->checksum_alg_before_fd == BINLOG_CHECKSUM_ALG_CRC32); } The find_type() call here will return 0 for checksum algorithms that are not known to the slave. Suggested fix: Change the code that checks the result of the SET @master_binlog_checksum = @@global.binlog_checksum Set checksum_alg_before_fd to OFF if an error is reported and UNKNOWN if there were no error but find_type in the excerpt above above returns 0. Either report an error and stop the slave or, if possible, report a warning and remove the checksum from the event before processing it.