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MySQL Replication Setup -  master / slave connectivity issue

Posted on 2016-09-05
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Last Modified: 2016-09-10
Hello,

I have configured two standalone MySQL instances mysqlmaster (host ip 192.168.159.141) & mysqlslave (host ip 192.168.159.142) on my VMware virtual machine running CentOS. I have created users 'siva' on both machines who can connect from any host ip (%). Granted ALL permissions for this user on both instances .

But my remote connectivity fails with following error,

[root@mysqlmaster siva]# mysql -u siva -p -h 192.168.159.142
Enter password:
ERROR 2003 (HY000): Can't connect to MySQL server on '192.168.159.142' (113)
[root@mysqlmaster siva]#

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'mysqlmaster' configuration
[mysqld]
bind-address = *
port=3306
server-id=1
validate_password_policy=LOW
log_bin=mysql-bin.log
binlog-do-db = repl01

'mysqlslave' configuration
[mysqld]
bind-address = *
port=3306
server-id=2
validate_password_policy=LOW

Connectivity tests i have performed ,
1) PING test from both instances is successful.
2) Telnet on 3306 fails on both instances to other instance.

Not sure if this can be done if the hosts are standalone & not under any domain controller.

Thanks
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Question by:Siva Dasari
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by:arnold
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Seems fine , did you run the command on the slave to establish the link, though you are missing info on which databases are to be replicated, MySQL db is not to be replicated.

On the master, show master status, on the slave show slave status.....
The database repl01 exists on the slave?
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by:Siva Dasari
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I haven't created repl01 DB on slave yet. Firstly I'm trying to establish remote connection to make sure master can reach slave & vice versa. I didn't proceed further because the remote connection itself fails ...
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by:arnold
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The db must exist, the connection is from the slave to the master, it is a pull setup, not a push setup.
Are you following a specific guide to setup master/slave?

What you should consider doing adding the index/increment settings just in the event you choose to switch the master/slave to master/master where the insertion can occur on either, while the replication is in both directions.
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by:arnold
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See replication write up, http://dev.mysql.com/doc/refman/5.5/en/replication-howto.html

auto_increment_increment=10
auto_increment_offset=starting value from 1-9
This will enable to have a 9 node circular replication master/master where an insert row in any will always have a unique identifier eliminating collision; two records having the same auto_incremented counter value.
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Author Comment

by:Siva Dasari
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Ok, let me put my question simple. Forget about replication setup for now.
Why I'm unable to make remote call / connection from instanceA to instanceB or vice versa? I know there is something blocking but not sure what it is though ...
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Assisted Solution

by:arnold
arnold earned 500 total points
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When you created the slva user, did you specify a hostname from which it San connect?

Grant replication on repl01.* to 'slva'@'%' ... This will allow slva to connect from any host.

If instead of '%' you used an IP address, slva will only be allowed to connect from that IP address/host provided if a database is part of the setting, it must be part of the command,

Try this instead of using MySQL,
telnet 192.168.159.x 3306
If you do not get a connection established, check firewall rules on each host, to make sure port 3306 incoming connections are allowed....
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Author Comment

by:Siva Dasari
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As I stated in my initial question the user is created with host as % so the connection can be accepted from any host & granted all permissions to the user. I made the telnet tests from A to B & B to A on 3306 port but the results are negative.

As you mention I will review the firewall settings & see if I can find something ...
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by:arnold
arnold earned 500 total points
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Which Linux distro are you using, sfw, iptables -L, ......... Will .......
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Siva Dasari earned 0 total points
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Thanks Arnold for your guidance on this issue.

Issue is now resolved after opening the port 3306 on which mysql is configured to listen & it is done on both the instances A & B ... below are the steps I have executed.
[siva@mysqlslave ~]$ sudo firewall-cmd --zone=public --add-port=3306/tcp --permanent
[sudo] password for siva:
success
[siva@mysqlslave ~]$ sudo firewall-cmd --reload
success
[siva@mysqlslave ~]$ firewall-cmd --list-all
public (default, active)
  interfaces: eno16777736
  sources:
  services: dhcpv6-client ssh
  [b]ports: 3306/tcp[/b]
  masquerade: no
  forward-ports:
  icmp-blocks:
  rich rules:

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Author Closing Comment

by:Siva Dasari
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The ports are blocked on both the instances A & B. I have opened them in the firewall rules which resolved the issue.
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