[sr-dev] git:master: db_cluster: new module for generic database clustering

[Marius Zbihlei]

On 03/27/2012 03:44 PM, Daniel-Constantin Mierla wrote:
> Module: sip-router
> Branch: master
> Commit: 201fc2d600e48fbb717531c79013c1b971f82d76
> URL:    http://git.sip-router.org/cgi-bin/gitweb.cgi/sip-router/?a=commit;h=201fc2d600e48fbb717531c79013c1b971f82d76
>
> Author: Daniel-Constantin Mierla<miconda at gmail.com>
> Committer: Daniel-Constantin Mierla<miconda at gmail.com>
> Date:   Tue Mar 27 14:38:57 2012 +0200
>
Hello Daniel,

I have a few questions regarding the db_cluster module and especially 
the way it deals with errors:

  For serial operation , lets consider two handlers DB1 and DB2 with the 
same priority. For the first write operation DB1 lets presume that 
itfails so the insert is done on DB2 (network congestion, mysql deadlock 
etc). But for a serial select the first DB1 is chosen (I looked thru the 
code and I see no ways of caching the initial error) and this means that 
the info returned from DB1 (it might be insert_update or update so info 
might be also present in DB1). How does the module handle this?

Same scenarios and question  I think it applies with round-robin mode as 
well.

The way we do this in p_usrloc is by keeping a error counter per each 
handler that is associated with a state (on -off) and a timestamp (when 
it failed). This info can be used to disable usage of the DB handler( 
and later put the handler in Write-Only mode until the data is 
synchronized )

Cheers,
Marius

> Zbihlei Marius
>
> Head of
> Linux Development Services Romania
>
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