Re: do i need to set up mysql cluster for mysql-ha to work?
Fernando Ipar <[email protected]> Fri, 25 Mar 2005 01:41:05 -0200
| Newsgroups | gmane.comp.db.mysql.high-availability |
|---|---|
| Message-ID | <[email protected]> |
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You're right, LOAD DATA FROM MASTER works just for MyISAM, but the
innodb snapshot will work just as fine. <br>
In fact, the 'high level' algorithm would be: <br>
- stop data modifying queries on the slave (by issuing a lock, stopping
the service, whatever)<br>
- synch the fixed master with the slave ('load data..', 'ibbackup',
'tar',...)<br>
-<b> make sure the MASTER_LOG_FILE and MASTER_LOG_POS values are correct</b>.
I write this on bold, since LOAD DATA FROM MASTER<br>
takes care of this automatically, but if you do a backup on your own,
these values will be outdated<br>
- reconfigure the master/slave relationship<br>
- restart the service<br>
<br>
I would be interested in providing different methods to synch back to a
'fixed master', according to the configuration (mysql version, table
handler, ...), so if you get this working with ibbackup and you'd like
to share those scripts, they'll be welcome :). <br>
<br>
Regards, <br>
Fernando. <br>
<br>
Xinhuan Zheng wrote:
<blockquote cite="[email protected]"
type="cite">
<pre wrap="">Thanks for explaination. So actually the failover is composed of 1)
fake ip on slave and serve client requests 2) integrate master back.
The step 1 is clear to me. The step 2 you said using 'load data from
master'. That one just works for MyISAM. If i'm using InnoDB (mysql
4.1.10), i'm not sure if that works. Do i need to take innodb snapshot
(we already have ibbackup tool installed) and sync the snapshot from
slave to 'fixed master'? thanks again. --xinhuan
On Wed, 23 Mar 2005 20:06:40 -0200, Fernando Ipar
<a class="moz-txt-link-rfc2396E" href="mailto:[email protected]"><[email protected]></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> Exactly.
Right now, the script only handles the slave takeover when the master
fails.
I wasn't clear with the 'autimatic fixed master integration' thing :).
By 'fixed master' I mean a replacement for the failed master that caused
the slave to takeover (meaning that you solve whatever problem caused the
master to fail, so it's now 'fixed').
By 'automatic integration' I mean having this server integrate back into
the cluster and begin working again as master, automatically.
However, using mysql >= 4.x, you can easily do this like this: (this is
what's being scripted right now, and what will go into the next release
after testing)
- configure the fixed machine to work as slave to the 'new master' (the
slave that did the takeover)
- STOP THE 'new master'. This is important because we're going to update
the original master with the changes that took place during the repair
period, and we don't want any more changes to happen in the meantime.
- do a LOAD DATA FROM MASTER on the fixed box
- configure it as master
- configure the slave again as slave to the fixed box
- (hopefully) get it all working :)
I'm sorry if my words were confusing, I have some trouble putting my ideas
into text. Fortunately, it's easier to put them down as code ;).
Regards,
Fernando.
Xinhuan Zheng wrote:
what do you mean by automatic fixed master integration? I want to promote a
slave automatically and later on when died master is fixed, let the master
temporarily a slave to get all the updates. When this is done, switch
master/slave back to their original role. The take_over.sh seems not having
those functions, right? On Wed, 23 Mar 2005 16:57:14 -0200, Fernando Ipar
<a class="moz-txt-link-rfc2396E" href="mailto:[email protected]"><[email protected]></a> wrote:
The takeover is invoked at slave_routine.sh, line 104. The takeover script
just configures the cluster IP on the slave, so that new client requests are
processed in this 'new' master (By the way, this means that, at the moment
of a master failure, clients will experience problems like timeouts or
connection errors. The lenght of this error period can be configured, using
the SLAVE_SLEEP_TIME and SSH_PATIENCE parameters. You can read through the
takeover.sh script if you want to know more about the takeover process. ARP
spoofing is used in cases where the master won't release the cluster IP
(there's a comment on slave_routine.sh briefly explaining one possible
scenario for this). What we don't have now in the scripts is automatic
integration of a fixed master. I'm working on this right now for a customer,
and once the code is deemed stable, a new release will be ready. However,
this method will only work automatically for MySQL versions 4.x or higher.
Regards, Fernando. Xinhuan Zheng wrote:
Good explaination. Now i understand how shared ip works. I have another
question: it seems to me that the shared ip is taken over by slave, how does
master and slave role get switched? In read world, I'd like to switch a died
master to slave and promote a slave to a master temporarily and once master
is fixed and get all updates from its slave, switch them back. I don't see
all these in the scripts or probably I miss them. Can you please advise?
thanks very much. --xinhuan -- ---------------------------- Fernando Ipar -
Director Seriema Systems Av. Italia 6201 601 3724 / 135
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</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
----------------------------
Fernando Ipar - Director
Seriema Systems
Av. Italia 6201
601 3724 / 135
<a class="moz-txt-link-abbreviated" href="http://www.seriema-systems.com">www.seriema-systems.com</a>
-----------------------------
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