[pgpool-hackers: 2287] Re: RFC: New health check implementation

[Muhammad Usama]

On Tue, Apr 25, 2017 at 7:24 PM, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> 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.
>

Sure thanks, And yes you are right  the health_check_period doesn't needs
to go in shared memory,

You can just push the structure related changes for the health_check_period
parameters and I will make it configurable, that way it will save you the
time and also I will be able to test the changes before pushing the changes.

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
>
> > 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
> >> >>> _______________________________________________
> >> >>> pgpool-hackers mailing list
> >> >>> pgpool-hackers at pgpool.net
> >> >>> http://www.pgpool.net/mailman/listinfo/pgpool-hackers
> >>
>
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