How to Report Replication Bugs or Problems
When you have determined that there is no user error involved, and replication still either does not
work at all or is unstable, it is time to send us a bug report. We need to obtain as much information as
possible from you to be able to track down the bug. Please spend some time and effort in preparing a
good bug report.
If you have a repeatable test case that demonstrates the bug, please enter it into our bugs database
using the instructions given in Section 1.7, “How to Report Bugs or Problems”. If you have a “phantom”
problem (one that you cannot duplicate at will), use the following procedure:
1. Verify that no user error is involved. For example, if you update the slave outside of the slave
thread, the data goes out of synchrony, and you can have unique key violations on updates. In
this case, the slave thread stops and waits for you to clean up the tables manually to bring them
into synchrony. This is not a replication problem. It is a problem of outside interference causing
replication to fail.
2. Run the slave with the --log-slave-updates  and --log-bin  options. These
options cause the slave to log the updates that it receives from the master into its own binary logs.
3. Save all evidence before resetting the replication state. If we have no information or only sketchy
information, it becomes difficult or impossible for us to track down the problem. The evidence you
should collect is:
• All binary log files from the master
• All binary log files from the slave
• The output of SHOW MASTER STATUS from the master at the time you discovered the problem
• The output of SHOW SLAVE STATUS from the slave at the time you discovered the problem
• Error logs from the master and the slave
4. Use mysqlbinlog to examine the binary logs. The following should be helpful to find the problem
statement. log_file and log_pos are the Master_Log_File and Read_Master_Log_Pos
values from SHOW SLAVE STATUS.
shell mysqlbinlog --start-position=log_pos log_file | head
After you have collected the evidence for the problem, try to isolate it as a separate test case first. Then
enter the problem with as much information as possible into our bugs database using the instructions at
Section 1.7, “How to Report Bugs or Problems”.
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