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Hi,<br>
<br>
Ruzsinszky Attila wrote:
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">Hi,
</pre>
<blockquote type="cite">
<pre wrap="">A MySQL Multi-Master architecture for a 2 node setup brings a lot of
configuration and administration overhead and has no conflict detection or
resolution. Integrating such a setup with Pacemaker only adds to the
</pre>
</blockquote>
<pre wrap=""><!---->Yes, I found it.
The real story: I want to learn clustering with a 2 node failover cluster.
I configured the cluster by DMC (DRBD Management Console).
I used the GUI configuring a MySQL service. It was almost unsuccessfull
which wasn't a surprise for me. After that I started to read some HowTo,
WEB page, etc. for help. I found someone from #mysql-nbd channel who
helped me and adviced me using M-M MySQL config but he doesn't know
almost anything about Pacemaker (He uses RH cluster).
</pre>
</blockquote>
And now (officially) RHCS can also use Pacemaker
<a class="moz-txt-link-freetext" href="http://theclusterguy.clusterlabs.org/post/1551292286">http://theclusterguy.clusterlabs.org/post/1551292286</a><br>
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">
After we did the working M-M config I started pacemaker and I could see
MySQL is working. I could connect to the commonIP and I could create a
test DB. Everything seemed all right until I put standby the master node
(from pacemaker point of view). In that moment mysqld started to "blinking"
between working and not working state because pacemaker always restarted
the process.
In the messages file I clould see some lines about missing privs. (RELOAD
and SUPER).
So I'm here now.
</pre>
</blockquote>
Yeah, like I said, Master-Master and Pacemaker without a proper
resource agent will cause issues. <br>
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">server. Even the LSB script doesn't handle a Multi-Master setup. You'd have
to write a custom resource agent, and it would probably fit your setup and
your setup alone, meaning it couldn't be widely used for other setups, I
know I had to make some modifications to the mysql resource agent and those
changes were specific to my setup.
</pre>
</blockquote>
<pre wrap=""><!---->No, I don't want to write scripts. I'm not a programmer. I just want
to try out a
new tech for MySQL clustering except MySQL+DRBD.It is clear for me
theoretically. The files of mysqld reside on the common dir. which was switched
by DRBD. Is that right?
</pre>
</blockquote>
Yes.<br>
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">MySQL Cluster is a choice, it could be integrated with Pacemaker, although I
</pre>
</blockquote>
<pre wrap=""><!---->Now I don't want MySQL Cluster. I think it is a bigger task for me.
</pre>
<blockquote type="cite">
<pre wrap="">Anyways, this is just to get a feel for what's involved in the process, and
how Pacemaker would fit the picture, at least from my point of view.
</pre>
</blockquote>
<pre wrap=""><!---->OK
</pre>
<blockquote type="cite">
<pre wrap="">I would recommend all questions related to MySQL Cluster, Replication,
Multi-Master be directed to the appropriate mailing lists though, and if you
</pre>
</blockquote>
<pre wrap=""><!---->As I mentioned I've got an M-M config from #mysql-nbd.
The recent problem is MySQL (M-M) + Pacemaker.
</pre>
</blockquote>
Back to square one, don't pass go, don't collect $200. No resource
agent, big problems. Now let me explain this, a 2-node Multi-Master
MySQL setup means setting up every node as both Master and Slave, node
1's Master replicates asynchronously to node 2's Slave and node 2's
Master replicates asynchronously to node 1's Slave. The replication
channels between the two are not redundant, nor do they recover from
failure automatically and you have to manually set the
auto-increment-increment and auto-increment-offset so that you don't
have primary key collisions.<br>
<br>
Now imagine a resource agent and what it should do to keep the
resources up. First you need to check periodically (monitor) the
replication channels, if they fail, you must determine which node has
the most recent information and make sure that first it's information
is sent to the other node via the Slave replication channel, then
activate the reverse Master-Slave channel, otherwise you'd be in a
MySQL 'split-brain' situation, where each node has information written
to it and the database now contains different views on each server.
Looking at how DRBD handles these kinds of things is one way to go
about it, but ... it's a huge task and there are a lot of things that
can go terribly wrong.<br>
<br>
So again, for the third time, the problem is not the Multi-Master
setup, nor it is Pacemaker, it's just a very specific use case for
which a resource agent wasn't written.<br>
<br>
Regards,<br>
<br>
Dan<br>
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">want to write a resource agent for a Multi-Master setup, by all means, do
share :)
</pre>
</blockquote>
<pre wrap=""><!---->No, I don't want. I'm a beginner both in clustering and MySQL.
</pre>
<blockquote type="cite">
<pre wrap="">Hope this helps.
</pre>
</blockquote>
<pre wrap=""><!---->Yes, of course.
BTW.
If I want to solve the above problem can you help me? </pre>
</blockquote>
<blockquote
cite="mid:AANLkTikDCogGZG7xajOmgXzT3j_hwqQ6_TjONWHoodbS@mail.gmail.com"
type="cite">
<pre wrap="">Of course with my
strict error messages, config files, etc. I "feel" my M-M config is not
rock stable (I was able to brake the IO or SQL "channel" between the
two mysqld processes) so I don't know whether I want this type of setup.
TIA,
Ruzsi
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</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Dan FRINCU
Systems Engineer
CCNA, RHCE
Streamwide Romania
</pre>
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