[Pgpool-general] What are the causes of pgpool failover

[ProAce]

Hi there!

In my web server farm, I install pgpool in each web server ( 32
servers in total) and set configuration as replication without
load-balance.
And I turn on the health check function, check every 5 seconds, and
timeout is 30 seconds.

The web server farm has run for more than 2 months, and it seems
everything is OK, but I'm still worried that the pgpool health check
status is different at every web server.
I run some testing program and find the pgpool health check status
remains always the same at each web server.  :)

Here, I'd like to raise three questions.
Firstly, I want to know what causes will let pgpool turn to degeneration mode.
Maybe I can do someting to monitor those causes on each server.

The second question is how many postgresql's folders/files must be
synchronized after degeneration mode?
All the data folders/files ? Or just some specific folders/files?

The third question is as follows.
I once had the two db have different data on purpose, and the pgpool
notified me that the data were mismatched between two db servers, and
interrupted the request. (1) How does the pgpool check it?
(2) I also want to know If the check function is trustworthy. Because
even some pgpool turn into  degeneration mode while others do not,
when the pgpool tell me the data were mismatched, I can still perform
fail back procedure immediately.

Thanks a million for your help!

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Appendix:
Some configuration modified by me as below:
num_init_children = 32
replication_mode = true
health_check_timeout = 30
health_check_period = 5
log_statement = true