Home / server / Questions / 266876
In Process
simon
Asked: 2011-05-05 12:09:33 +0800 CST

MySQL simple replication problem: 'show master status' produces 'Empty set'?

  • 772

I've been setting up MySQL master replication (on Debian 6.0.1) following these instructions faithfully: http://www.neocodesoftware.com/replication/

I've got as far as:

mysql > show master status;

but this is unfortunately producing the following, rather than any useful output:

Empty set (0.00 sec)

The error log at /var/log/mysql.err is just an empty file, so that's not giving me any clues.

Any ideas?

This is what I have put in /etc/mysql/my.cnf on one server (amended appropriately for the other server):

server-id = 1
replicate-same-server-id = 0
auto-increment-increment = 2
auto-increment-offset = 1
master-host = 10.0.0.3
master-user = <myusername>
master-password = <mypass>
master-connect-retry = 60
replicate-do-db = fruit
log-bin = /var/log/mysql-replication.log
binlog-do-db = fruit

And I have set up users and can connect from MySQL on Server A to the database on Server B using the username/password/ipaddress above.

mysql replication database master-slave

4 Answers

  1. Interestingly, I have mysql running on my PC with binary logs not enabled. I did the following:

    Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 19
Server version: 5.5.12 MySQL Community Server (GPL)

Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show master status;
Empty set (0.00 sec)

mysql> show binary logs;
ERROR 1381 (HY000): You are not using binary logging

mysql>

    As shown, since MySQL shows "Empty Set" for SHOW MASTER STATUS; because binary logging was not enabled. That's obvious given the configuration I have.

    First thing you should do is make sure the error log has a specific folder

    [mysqld]
log-error=/var/log/mysql/mysql.err
log-bin = /var/log/mysql/mysql-replication.log

    Then run the following:

    service mysql stop
mkdir /var/log/mysql
chown -R mysql:mysql /var/log/mysql
service mysql start

    Then in the mysql client run these SQL Commands

    SHOW MASTER STATUS;
SHOW BINARY LOGS;

    If you get the same output I had before, then MySQL cannot write binary logs to the designated folder. Your dilemma becomes why MySQL cannot write to /var/log.

    This is not a full answer but I hope this helps.

    • 8

  2. If thhe Mysql version is >5.0, your replication settings master-host, master-user, master-password and a few others in your my.cnf will be ignored. Use CHANGE MASTER TO for initial replication setup.

    Compare http://dev.mysql.com/doc/refman/5.1/en/replication-howto-slaveinit.html

    • 1

  3. Your setting for log-bin is incorrect, so MySQL can't write binary logs. It isn't a filename, it is a partial filename pattern, to which MySQL will prepend a directory and append a sequence number and extension. The usual setting is something like

    log-bin=log-bin

    Check the manual.

    • 0

  4. If you are using Amazon RDS or Aurora, remember to reboot the writer instance after applying bin_log in cluster parameter.

    This needs to be done manually. Rebooting writer instance will also cause read replicas to reboot.

    Before rebooting you will get Empty set.

    • 0