| Bug #27101 | mysqlhotcopy --record_log_pos retrieves wrong slave parameters | ||
|---|---|---|---|
| Submitted: | 13 Mar 2007 19:01 | Modified: | 22 Apr 2008 13:55 |
| Reporter: | Alex Tomic | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: Command-line Clients | Severity: | S3 (Non-critical) |
| Version: | 5.0.40-BK, 5.0.27 | OS: | Linux (Linux) |
| Assigned to: | Iggy Galarza | CPU Architecture: | Any |
| Tags: | Contribution, mysqlhotcopy, replication | ||
[29 Mar 2007 6:39]
Valeriy Kravchuk
Thank you for a problem report and contributed patch. Verified with code review on latest 5.0.40-BK sources - mysqlhotcopy code is still the same. Your patch is surely worth developers' consideration.
[5 Mar 2008 19:13]
Andrei Elkin
Imo the problem was identified correctly. The fix is correct as well. Show slave status of mysql-4.0 output displays the necessary fields so that the patch should be applicable and workable with early version of the server.
[7 Mar 2008 20:46]
Bugs System
A patch for this bug has been committed. After review, it may be pushed to the relevant source trees for release in the next version. You can access the patch from: http://lists.mysql.com/commits/43628 ChangeSet@1.2581, 2008-03-07 15:45:40-05:00, iggy@amd64.(none) +1 -0 Bug #27101 mysqlhotcopy --record_log_pos retrieves wrong slave parameters - Make sure mysqlhotcopy doesn't create unrestorable slaves.
[27 Mar 2008 22:04]
Bugs System
Pushed into 5.1.24-rc
[27 Mar 2008 22:11]
Bugs System
Pushed into 5.0.60
[28 Mar 2008 11:10]
Bugs System
Pushed into 6.0.5-alpha
[22 Apr 2008 13:55]
Paul DuBois
Noted in 5.0.60, 5.1.24, 6.0.5 changelogs. For the --record_log_pos option, mysqlhotcopy now determines the slave status information from the result of SHOW SLAVE STATUS by using the Relay_Master_Log_File and Exec_Master_Log_Pos values rather than the Master_Log_File and Read_Master_Log_Pos values. This provides a more accurate indication of slave execution relative to the master.
Description: From perldoc for mysqlhotcopy, with relevant portion identified with ****: --record_log_pos log-pos-table Just before the database files are copied, update the record in the log-pos-table from the values returned from "show master status" and "show slave status". The master status values are stored in the log_file and log_pos columns, and establish the position in the binary logs that any slaves of this host should adopt if ini- tialised from this dump. **** The slave status values are stored in master_host, master_log_file, and master_log_pos, and these are useful if the host performing the dump is a slave and other sibling slaves are to be initialised from this dump. **** In order to restore a consistent backup of the master from a dump of the slave, we would want to know the log position and coordinate that the slave's SQL thread had executed, not where the I/O thread had retrieved from the master. See http://forums.mysql.com/read.php?26,143765,143765#msg-143765 for my posting to the MySQL forums about this problem for more details on why I think this is a bug. How to repeat: Run mysqlhotcopy with --record_log_pos option on a slave database for the purposes of restoring a new slave against master . Suggested fix: Not sure what is the best way of submitting a patch, but here is a diff between the 5.0.27 file and my fixed file that I tested successfully on one of my 5.0 servers (basically just change the two parameters that are read from $row_hash ). I've upgraded all my 4.x servers so I'm not able to test backward compatibility, but both new parameters are in the 4.0 docs for 'show slave status' so I assume it should work: $ diff -u mysqlhotcopy mysqlhotcopy.new --- mysqlhotcopy 2007-03-13 14:15:51.000000000 -0400 +++ mysqlhotcopy.new 2007-03-13 14:13:26.000000000 -0400 @@ -754,7 +754,7 @@ = @{$row_hash}{ qw / Master_Host Log_File Pos / }; } else { ($master_host, $log_file, $log_pos ) - = @{$row_hash}{ qw / Master_Host Master_Log_File Read_Master_Log_Pos / }; + = @{$row_hash}{ qw / Master_Host Relay_Master_Log_File Exec_Master_Log_Pos / }; } my $hostname = hostname();