[pgpool-hackers: 2286] Re: RFC: New health check implementation

[Tatsuo Ishii]

Hi Usama,

> Hi Ishii-San
> 
> I am working on config framework modification to allow same name parameters
> with and without index postfix, I am almost done with the framework related
> changes.

Thanks!

> And now for testing I need to add one such parameter and I was thinking
> instead of using a dummy configuration variable for testing I would rather
> add the *health_check_period* and *health_check_period[idx]* so that you
> can also use it.
> For that can you tell me where do you want to create health_check_period
> variable for each backend? Is BackendInfo structure is the right place?

I'm working on it for the part. I will push it tomorrow. BTW, unlike
BackendInfo, the structure does not need to live on the shared memory.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

> Thanks
> Best Regards
> 
> 
> On Mon, Apr 24, 2017 at 7:42 AM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> 
>> >> On 21-Apr-2017, at 4:31 AM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
>> >>
>> >> Usama,
>> >>
>> >> Is it possible to have following config parameter at the same time?
>> >> My feeling is we can't because current implementation of config
>> >> handling does not allow it.
>> >>
>> >> health_check_period = 10
>> >> health_check_period0 = 5
>> >
>> > Yes, having the same named configuration parameter with and without
>> index postfix would cause problem with the current implementations, but if
>> we want to support this I can tweak the configuration framework to allow
>> that.
>>
>> That would be desirable.
>>
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
>>
>> > Thanks
>> > Best regards
>> > Muhammad Usama
>> >
>> >>
>> >> Best regards,
>> >> --
>> >> Tatsuo Ishii
>> >> SRA OSS, Inc. Japan
>> >> English: http://www.sraoss.co.jp/index_en.php
>> >> Japanese:http://www.sraoss.co.jp
>> >>
>> >>> Hi,
>> >>>
>> >>> This is a Request for Comments on the new implementation of health
>> >>> check aiming for Pgpool-II 3.7.
>> >>>
>> >>> Problems:
>> >>>
>> >>> Current implementation of health check is a single serial processing
>> >>> for all of database nodes. This implies some limitations for health
>> >>> check process: 1) it is not possible to specify different health check
>> >>> configuration values for each database node, 2) node failure detection
>> >>> may take longer. For example, if it takes 10 seconds before detecting
>> >>> node 0 failure, then detecting node 1 failure will be delayed at least
>> >>> 10 seconds because it starts node failure detection after node 0.
>> >>>
>> >>> The solution:
>> >>>
>> >>> Allow to specify health check parameters for each node. Pgpool.conf
>> >>> will look like:
>> >>>
>> >>> health_check_period0 = 10
>> >>> health_check_timeout0 = 20
>> >>> :
>> >>> :
>> >>>
>> >>> where "0" means database node 0 (similar concept as "backend_*0
>> >>> parameters).
>> >>>
>> >>> To make admin's life easier, current parameters can be used as
>> >>> well. Suppose there are 3 nodes, and we have:
>> >>>
>> >>> health_check_period = 10
>> >>> health_check_period0 = 5
>> >>>
>> >>> then health_check_period for node 1 and 2 will be 10, while
>> >>> health_check_period for node 0 will be 5. So parameter names without
>> >>> node id works as a "global variable".
>> >>>
>> >>> The implementation:
>> >>>
>> >>> Create separate child process of pgpool main process and let do the
>> >>> heal check job for each database node. Once the health check child
>> >>> process detects node failure, it signals to main process and main
>> >>> process will perform failover.
>> >>>
>> >>> This architecture makes pgpool main process simpler and robust, while
>> >>> earlier detection of node failure by the health check child process.
>> >>>
>> >>> Comments and suggestions are welcome.
>> >>>
>> >>> Best regards,
>> >>> --
>> >>> Tatsuo Ishii
>> >>> SRA OSS, Inc. Japan
>> >>> English: http://www.sraoss.co.jp/index_en.php
>> >>> Japanese:http://www.sraoss.co.jp
>> >>> _______________________________________________
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>> >>> http://www.pgpool.net/mailman/listinfo/pgpool-hackers
>>