Re: Unmonitored Master
Posted by: Oliver Candelario
Date: December 23, 2011 12:28AM

Hi Mark,

Thank you for the reply. Our problem falls on your #2 suggestion. Yes we are using Public IP binded to the masters local IP. The (2) servers are in different colocations. Now I understand why it was not discovered properly. Is there any workaround on this kind of case?

Hope you can still reply, really appreciate it.

Thank you again,
Oliver

Mark Leith Wrote:
-------------------------------------------------------
> Hey Oliver,
>
> MEM tries to do topology discovery in a couple of
> different ways:
>
> 1) It first tries to read the master.info file
> from the slave server, and use the credentials
> within it to connect to the master server, and
> select from the mysql.inventory table that every
> MEM agent creates. This requires that the agent is
> started as the same user as MySQL (so that it can
> read the master.info in the data directory), and
> that slave user has SELECT privileges against the
> mysql.inventory table as well.
>
> 2) If the above does not work, we fall back to IP
> matching - we read the Master_host / Master_port
> from SHOW SLAVE STATUS on the slave, if
> Master_host is not an IP address we do an IP
> lookup based on the host name, and report that
> back as the "Master_IP" to the MEM server. Then,
> every single agent reports about all of the
> network interfaces on each machine, so we use all
> of this to generate the topology based on where
> the IPs are pointing.
>
> The first solution is fairly bullet proof, there's
> not much that stops it from getting the right
> topologies, given the right permissions to read
> everything.
>
> The second solution has problems when using things
> like virtual IPs - the slave may connect to a
> virtual IP through to the master, but the end
> point IP address on the master that we know about
> is only as reported by the agent installed upon
> that master - it doesn't know about the virtual IP
> at the network layer before it.
>
> In summary - I'd make sure your agent is started
> as the user MySQL is started as (the "mysql" user
> generally), and that the slave user on the master
> has SELECT privileges on mysql.inventory. That
> will give the most reliable topology discovery.
>
> Regards,
>
> Mark

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