Question

I have to set up a new mysql replication replicating two databases. So I have this script which locks tables, makes a dump and unlocks them.

runme.sh

mysql -uxxx -pxxx < 1.sql >> logpos.txt
mysqldump -uXXX -pXXX db1 > db1.sql
mysqldump -uXXX -pXXX db2 > db2.sql
mysql -uxxx -pxxx < 2.sql >> logpos.txt

first sql file locks tables and exports master status:

1.sql

FLUSH TABLES WITH READ LOCK;
SHOW MASTER STATUS;

second file exports master status and unlocks tables

2.sql

SHOW MASTER STATUS;
UNLOCK TABLES;

the result looks like this:

logpos.txt

File    Position        Binlog_Do_DB    Binlog_Ignore_DB
mysql-bin.000335        49106285        fli_search,flimmit
File    Position        Binlog_Do_DB    Binlog_Ignore_DB
mysql-bin.000335        49139991        fli_search,flimmit

Question:
How can the log position change while tables are locked?

Server version:  5.0.51a-24+lenny4-log (Debian)

I could do mysqldump for multiple databases and add –master-data, but I somehow felt unsafe because there are different database formats involved and I couldn’t really find out how mysqldump –master-data behaves with multiple databases. So I had this script and got different log positions…. any idea why? I cannot use this to set up a replication…

UPDATE:

I finally decided to set up replication with mysqldump --master-data --databases db1 db2
the dump was created tonight at 1 am.
today at about 10 am i set up the slave. i totally cleared the databases (dropped all tables) and imported the dump, which automatically set the master log file and log pos correctly. i checked that its the same as in the sql dump. everything looked fine.
of course i stopped the slave before importing (otherwise i couldnt import the dump with change master to statement anway).
i started the slave and eveyrthing looked just fine. the log pos increased, the seconds behind master decreased and went to 0 and some test data was replicated correctly.

but a major update from today ~7am (the time window between the dump creation and importing) was just missing. it pruned old records from a table, on the slave they were still present…
any idea why?

any additional information needeD? comment…

Answer 1

looks like i also have to do:

FLUSH TABLES WITH WRITE LOCK;

the master data switch seems to be unrelyable…