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Message from discussion About cluster status while adding a new node
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Henrik Ingo  
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 More options Aug 8 2012, 3:18 am
From: Henrik Ingo <henrik.i...@avoinelama.fi>
Date: Wed, 8 Aug 2012 10:18:37 +0300
Local: Wed, Aug 8 2012 3:18 am
Subject: Re: [codership-team] About cluster status while adding a new node
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On Wed, Aug 8, 2012 at 12:23 AM, Sébastien Han <han.sebast...@gmail.com> wrote:
> Hello,

> I would like more precision about the
> When a node is about join the cluster, it sends a request throught the gcomm
> url to a current member of the cluster. The chosen node status will changed
> from JOINED to DONOR and apparently a FLUSH TABLES WITH READ LOCK is
> performed by the SST. I'm currently using the RSYNC method which seems to be
> the fastest one.

> My question is:

> -Does the full cluster in a READ-ONLY status or only the DONOR node? I ask
> this question because your wiki says that **only** the donor is locked and
> the Percona XtraDB docs says that the **entire** cluster is locked...

Of course only the donor is locked (and this is only in the case of
rsync method, for instance with the xtrabackup sst method the donor is
not locked).

> -What happen to the incoming requests? I use HAProxy in from of every nodes.
> Are they manage like writeset caching during state transfer? With those
> options: gcs.recv_q_hard_limit, gcs.recv_q_soft_limit, gcs.max_throttle.

Currently an incoming query to the donor, if you are using rsync sst,
will block and wait for its turn (or until it exceeds a lock timeout
and fails).
In the next release a new configuration option
wsrep_sst_donor_rejects_queries will be introduced. When set to TRUE,
the donor will immediately reject an incoming query with "Unknown
error". The benefit of this is that HAProxy can then immediately
discover such failure and re-route to another node.

See https://bugs.launchpad.net/codership-mysql/+bug/1002714 for more info.

henrik
--
henrik.i...@avoinelama.fi
+358-40-8211286 skype: henrik.ingo irc: hingo
www.openlife.cc

My LinkedIn profile: http://www.linkedin.com/profile/view?id=9522559


 
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