[Pgpool-hackers] Health check retries (patch)

[Matt Solnit]

Thanks!  English documentation patch is attached.  One comment:  I wrote "You need to reload pgpool.conf
if you change these settings", but in fact, I have no idea if this is true :-).  Please feel free to change as necessary.
     
-- Matt

On Nov 18, 2011, at 8:53 PM, Tatsuo Ishii wrote:

> Matt,
> 
> Thank you! The patch looks pretty good.  Patch committed with a few
> modications.
> http://git.postgresql.org/gitweb/?p=pgpool2.git;a=commit;h=55199bdfa7630cf9a5142703ef85ee7695bb4221
> 
> 1) While retrying, emit log(rather than debug message). This would be
> more usefull for DBA because it makes clear that pgpool tries to
> recover state. Here is a sampe message.
> 2011-11-19 13:23:12 LOG:   pid 10375: health check retry sleep time: 1 second(s)
> 
> 2) After successfull retry, emit a log.
> 2011-11-19 13:23:19 LOG:   pid 10375: after some retrying backend returned to healthy state
> 
> BTW, I think to make the new feature works better, it's best to turn
> on fail_over_on_backend_error because even if health checking retries,
> writing to backend socket causes immediate failover if
> fail_over_on_backend_error is set to off.
> 
> Also new_connection() was fixed because it caused immediate failover
> when trying to connect to backend despite fail_over_on_backend_error
> is set to on.
> 
> Could you provide English documentation for this?
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese: http://www.sraoss.co.jp
> 
>> Hi everyone.  In August, I wrote to the pgpool-general list (see below) asking if there was any
>> way to have pgpool-II retry a failed health check before promoting the slave.
>> 
>> I'm attaching a patch that adds this functionality.  Would anyone care to review it?  We've been
>> using it successfully in production for about 3 months now, and it's working great.
>> 
>> This is my first time submitting a patch to PostgreSQL or PgPool, so go easy :-).
>> 
>> Some comments:
>> - The purpose of this feature is to allow pgpool-II to handle brief networking interruptions
>>   without being "fooled" into thinking that the master node is down and the slave needs to
>>   be promoted.
>> - This patch adds two new configuration settings.
>> - The "health_check_max_retries" setting is the maximum number of times to retry a health
>>   check before giving up.
>> - The "health_check_retry_delay" is the amount of time (in seconds) to sleep between retries.
>> - The feature is turned *off* by default (health_check_max_retries defaults to 0, or no retries).
>> 
>> Patch is against git HEAD revision (commit 58043c962b8305507de0f450be74c24cbe4c8430).
>> 
>> Please let me know if you have any questions or comments.
>> 
>> -- Matt
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