[pgpool-hackers: 4228] Re: Issue with failover_require_consensus

[Tatsuo Ishii]

> Hi Usama,
> 
> I think I found an issue with failover_require_consensus. When this
> parameter is enabled, watchdog asks other watchdog to confirm the
> failover event. If other watchdog replies back and the originator
> watchdog can make a consensus, failover process begins. However, if no
> replies arrive before FAILOVER_COMMAND_FINISH_TIMEOUT expires, the
> failover request is discarded and failover will not begin. If this
> only happens once or twice, we could expect that subsequent health
> check would trigger failover. But actually this could repeat forever
> (which means failover never happens) if health_check_period is larger
> than FAILOVER_COMMAND_FINISH_TIMEOUT (currently 15 seconds). For
> example, if health_check_period = 30 seconds, and other watchdog node
> 1 starts 50 seconds after watchdog node 0 (suppose this is the leader
> node), then every time failover consensus request is made (suppose the
> time is t), it will be canceled at t + 15, because failover on
> watchdog node 1 will happen at time t + 20 ( = 50 - 30).
> 
> Since we allow other watchdog node joins a watchdog cluster anytime, I
> think this is not a behavior we expect.
> 
> Can we make FAILOVER_COMMAND_FINISH_TIMEOUT longer or disable the
> expiring when failover_require_consensus is on?

Attached is the patch for this.

> disable the
> expiring when failover_require_consensus is on?

It seems the patch solves the issue and passed all of regression
test. But I wonder if the patch will give unwanted side effects. What
do you think?

Best reagards,
--
Tatsuo Ishii
SRA OSS LLC
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp
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